Flag description file for Sun compiled SPECint2000 and SPECfp2000
binaries using the following compilers:
PGI Fortran 5.2
PathScale EKO Compiler Suite, Release 1.1
Red Hat gcc 3.5 ssa (from Red Hat Enterprise Linux WS 3 (AMD64))
SuSE optional gcc 3.3 (from SLES8 SP3)
----------------------------------------------------------------------------
PGI (Portland Group International) compiler 5.2 flags
----------------------------------------------------------------------------
+ACML Linking with AMD Core Math Library. Supplied with the PGI compiler 5.2
RM_SOURCES=lapak.f90
Remove the source file 'lapak.f90' in 178.galgel.
The optimization levels and their meanings are as follows:
-O0 A basic block is generated for each Fortran statement. No scheduling
is done between statements. No global optimizations are performed.
-O1 Scheduling within extended basic blocks is performed. Some register
allocation is performed. No global optimizations are performed.
-O2 All level 1 optimizations are performed. In addition, scalar
optimizations such as induction recognition and loop invariant motion
are performed by the global optimizer.
-O3 This level performs all level-one and level-two optimizations and
enables more aggressive hoisting and scalar replacement optimizations.
-fast Equivalent to "-O2 -Munroll=c:1 -Mnoframe -Mlre"
-fastsse Equivalent to "-fast -Mscalarsse -Mvect=sse -Mcache_align -Mflushz"
-Mcache_align
Align unconstrained objects of length greater than or equal to 16 bytes on
cache-line boundaries. An unconstrained object is a data object that is not
a member of an aggregate structure or common block. This option does
not affect the alignment of allocatable or automatic arrays.
Note: To effect cache-line alignment of stack-based local variables, the
main program or function must be compiled with -Mcache_align.
-Mfixed
Process source using Fortran90 freeform specifications.
-Mflushz
Set SSE MXCSR register to flush-to-zero mode.
-Mipa[=option[,option,...]]
Enable and specify options for InterProcedural Analysis (IPA). This
also sets the optimization level to a minimum of 2; see -O. If no
option list is specified, then it is equivalent to -Mipa=const. The
options are:
const (default) noconst
Enable (disable) propagation of constants across procedure
calls.
inline:n
Determine additional functions to inline, allowing up to n
levels of inlining.
fast
Chooses generally optimal -Mipa flags for the target
platform; use pgf90 -Mipa -help to see the equivalent
options. fast is equivalant to
-Mipa=align,arg,const,f90ptr,shape,globals,localarg,ptr
align noalign
Enable (disable) recognition when pointer targets are all
cache-line aligned, allowing better SSE code generation.
arg noarg
Remove (don't remove) arguments replaced by
-Mipa=ptr,const. -Mipa=noarg implies -Mipa=nolocalarg.
const (default) noconst
Enable (disable) propagation of constants across procedure
calls.
f90ptr nof90ptr
Enable (disable) Fortran 90 pointer disambiguation across
procedure calls.
globals noglobals
Analyze (don't analyze) which globals are modified by
procedure calls.
localarg nolocalarg
Enable (disable) feature to externalize local variables to
allow arguments to be replaced by -Mipa=ptr.
-Mipa=localarg implies -Mipa=arg.
ptr noptr
Enable (disable) pointer disambiguation across procedure
calls.
shape noshape
Perform (don't perform) Fortran 90 shape propagation.
-mp Enable OpenMP
-Mnoframe
Eliminate operations that set up a true stack frame pointer for functions.
-Mnosmart
Don't run the Smart assembly re-write tool to enable post-compilation
linear assembly scheduling and optimization
-Mscalarsse
Utilize the SSE (Streaming SIMD(Single Instruction Multiple Data)
Extensions) and SSE2 instructions to perform the operations coded.
This assumes the user has an assembler capable of interpreting SSE/SSE2
instructions, as in later versions of Linux. This implies -Mflushz.
-Munroll
Invokes the loop unroller. This also sets the optimization level to 2
if the level is set to less than 2.
c:m Instructs the compiler to completely unroll loops with a
constant loop count less than or equal to m, a supplied constant.
If this value is not supplied, the m count is set to 4.
n:u Instructs the compiler to unroll u times, a loop which is
not completely unrolled, or has a non-constant loop count.
If u is not supplied, the unroller computes the number of times a
candidate loop is unrolled.
-Mvect=sse
Instructs the vectorizer to search for loops, and where possible,
use the SSE or SSE2 and prefetch instructions
(depending on which processor is targeted).
-Mlre[=assoc|noassoc] -Mnolre
Enable (disable) loop-carried redundancy elimination. The assoc
option allows expression reassociation, and the noassoc option
disallows expression reassociation.
----------------------------------------------------------------------------
PathScale EKO Compiler Suite, Release 1.1
----------------------------------------------------------------------------
PathScale compiler flag disclosure in this file is an excerpt from
"PathScale EKO Compiler Suite (Fortran, C and C++ compilers)
flag descriptions, for SPEC CPU2000 submissions."
Copyright 2003, 2004 PathScale, Inc. All Rights Reserved.
PathScale EKO Compiler Suite (Fortran, C and C++ compilers)
flag descriptions, for SPEC CPU2000 submissions.
Portability Flags:
-DSPEC_CPU2000_LP64 Compile using LP64 programming model.
-DLINUX_i386 Linux Intel system, use "long long" as
64bit variable.
-DHAS_ERRLIST Prog env provides specification for
"sys_errlist[]".
-DSPEC_CPU2000_NEED_BOOL Use SPEC provided definition of the boolean type.
-DSPEC_CPU2000_LINUX_I386 Compile for an I386 system running Linux.
-DPSEC_CPU2000_GLIBC22 Compatibility with 2.2 & later versions of glibc
-DSYS_IS_USG Specifies that the operating system is
USG compliant.
-DSYS_HAS_TIME_PROTO Do not explicitly declare time().
-DSYS_HAS_SIGNAL_PROTO Do not explicitly #include <signal.h>
-DSYS_HAS_IOCTL_PROTO Do not explicitly declare ioctl().
-DSYS_HAS_ANSI System is ANSI compliant.
-DSYS_HAS_CALLOC_PROTO Do not explicitly declare calloc().
-fixedform tells f90 compiler to use fixed format
(F77 72 column format), instead of F90 free format.
-DWANT_STDC_PROTO Use function prototypes as in standard C.
Optimization Flags:
Some suboptions either enable or disable the feature. To enable a feature,
either specify only the suboption name or specify =1, =ON, or =TRUE. Disabling
a feature, is accomplished by adding =0, =OFF, or =FALSE. These values are
insensitive to case: 'on' & 'ON' mean the same thing. Below, ON & OFF indicate
the enabling or disabling of a feature.
-CG[:...]
Code Generation option group: control the optimizations
and transformations of the instruction-level code generator.
-CG:cflow=(ON|OFF)
A value of OFF disables control flow optimization in the code
generation. Default is ON.
-CG:gcm=(ON|OFF)
Specifying OFF disables the instruction-level global code
motion optimization phase. The default is ON.
-CG:local_fwd_sched=(ON|OFF)
Changes the instruction scheduling algorithm to work forward
instead of backward for the instructions in each basic block.
The default is OFF.
-CG:p2align_freq=n
Aligns branch targets based on execution frequency. This option
is meaningful only under feedback-directed compilation. The
default value n=0 turns off the alignment optimization. Any
other value specifies the frequency threshold at or above which
this alignment will be performed by the compiler.
-CG:prefetch=(ON|OFF)
Suppresses any generation of prefetch instructions in the code
generator. This has the same effect as -LNO:prefetch=0.
The default is ON.
-fb_create <prefix for feedback data files>
Used to specify that an instrumented executable program
is to be generated. Such an executable is suitable for
producing feedback data files with the specified prefix
for use in feedback-directed compilation (FDO). The commonly
used prefix is "fbdata". This is OFF by default.
-fb_opt <prefix for feedback data files>
Used to specify feedback-directed compilation (FDO) by extracting
feedback data from files with the specified prefix, which were
previously generated using -fb_create. The commonly used prefix
is "fbdata". This optimization is off by default.
-fno-math-errno
Do not set ERRNO after calling math functions that are executed
with a single instruction, e.g., sqrt. A program that relies
on IEEE exceptions for math error handling may want to use this
flag for speed while maintaining IEEE arithmetic compatibility.
This is implied by -Ofast. The default is -fmath-errno.
-INLINE:aggressive=(ON|OFF)
Tells the compiler to be more aggressive about inlining. The
default is -INLINE:aggressive=OFF.
-IPA[:...]
IPA option group: control the inter-procedural analyses and
transformations performed. Note that giving just the group name
without any options, i.e., -IPA, will invoke the interprocedural
analyzer. -IPA is off by default unless -Ofast is specified.
-ipa Same as -IPA alone.
-IPA:callee_limit=(n)
Functions whose size exceeds this limit will never be
automatically inlined by the compiler. The default is n=2000.
-IPA:ctype=(ON|OFF)
Turns on optimizations that speed up interfaces to the constructs
defined in ctype.h by assuming that the program will not be run
in a multi-threaded environment. The default is OFF.
-IPA:linear=(ON|OFF)
Sets linearization of array references. setting can be ON
or OFF. When inlining Fortran subroutines, IPA tries to map
formal array parameters to the shape of the actual
parameter. It may not always be able to always map it. In
the case that it cannot map the parameter, it linearizes the
array reference. By default, it will not inline such
callsites because they may cause performance problems. The
default is OFF.
-IPA:min_hotness=(n)
When feedback information is available, a call site to a
procedure must be invoked with a frequency that exceeds
the threshold specified by n before the procedure
will be inlined at that call site. The default is n=10.
-IPA:plimit=(n)
Inline calls to a procedure until the procedure has grown to
size of n. The default is 2500.
-IPA:space=(n)
Inline until a program expansion of n% is reached. This defaults
to 100.
-LNO:
option group specifies options and transformations performed
on loop nests. The -LNO: option group is enabled only if the -O3
option is also specified on the compiler command line.
-LNO:blocking[=(ON|OFF)]
Enable/disable the cache blocking transformation. The default
is on at -O3 or higher.
-LNO:fusion=n
Perform loop fusion, n: 0 - off, 1 - conservative, 2 - aggressive.
The default is 1.
-LNO:interchange[=(ON|OFF)]
Specifying OFF disables the loop interchange transformation in
the loop nest optimizer. Default is ON.
-LNO:opt=n
This option controls the LNO optimization level. n can be one of
the following:
0 = Disables nearly all loop nest optimizations
1 = Performs full loop nest transformations (default)
-LNO:ou_prod_max=n
Indicates that the product of unrolling of the various outer
loops in a given loop nest is not to exceed n, where n is a
positive integer. The default is 16.
-LNO:prefetch[=(0|1|2|3)]
Specify level of prefetching.
0 = Prefetch disabled.
1 = Prefetch is done only for arrays that are always
referenced in each iteration of a loop, the default.
2 = Prefetch is done without the above restrictions.
3 = Most aggressive.
-LNO:prefetch_ahead=n
Prefetch n cache line(s) ahead. The default is 2.
-LNO:sclrze=(ON|OFF)
Turns on/off the optimization that replaces an array by a scalar
variable. The default is ON.
-m32
Generates code according to the 32-bit ABI, also known as x86
or IA32.
-O or -O2
Turn on extensive optimization. The optimizations at this level are
generally conservative, in the sense that they (1) are virtually
always beneficial, (2) provide improvements commensurate to the
compile time spent to achieve them, and (3) avoid changes which
affect such things as floating point accuracy.
-O3
Turn on aggressive optimization. The optimizations at this level
are distinguished from -O2 by their aggressiveness, generally
seeking highest-quality generated code even if it requires extensive
compile time. They may include optimizations which are generally
beneficial but occasionally hurt performance. This includes but
is not limited to turning on the Loop Nest Optimizer, -LNO:opt=1,
and setting -OPT:ro=1:IEEE_arith=2:Olimit=9000:reorg_common=ON.
-Ofast Equivalent to "-O3 -ipa -OPT:Ofast -fno-math-errno." -OPT:Ofast is
described below.
-OPT:alias=<name>
Specifies the pointer aliasing model to be used. By
specifiying one or more of the following for <name>, the
compiler is able to make assumptions throughout the compilation:
typed Assume that the code adheres to the ANSI/ISO C
standard which states that two pointers of different
types cannot point to the same location in memory.
This is on by default when -Ofast is specified.
restrict Specifies that distinct pointers are assumed
to point to distinct, non-overlapping objects.
This is off by default.
disjoint Specifies that any two pointer expressions are
assumed to point to distinct, non-overlapping objects.
This is off by default.
-OPT:div_split=(ON|OFF)
Enable/disable changing x/y into x*(recip(y)). This is
OFF by default.
-OPT:goto=(OFF|ON)
Disable/enable the conversion of GOTOs into higher level
structures like FOR loops. The default is ON for -O2 or higher.
-OPT:IEEE_arithmetic,IEEE_arith=(n)
specify level of conformance to IEEE 754 floating pointing
roundoff/overflow behavior. n can be one of the following:
1 Adheres to IEEE accuracy. This is the default when
optimization levels -O0, -O1 and -O2 are in effect.
2. May produce inexact result not conforming to IEEE 754.
This is the default when -O3 is in effect.
3. All mathematically valid transformations are allowed.
-OPT:Ofast
Use optimizations selected to maximize performance.
Although the optimizations are generally safe,
they may affect floating point accuracy due to rearrangement
of computations. This effectively turns on the following
optimizations:
-OPT:ro=2:Olimit=0:div_split=ON:alias=typed -TARG:msse2=on
-OPT:Olimit=(n)
Disable optimization when size of program unit is > n. When n
is 0, program unit size is ignored and optimization process
will not be disabled due to compile time limit. The default is
0 when -Ofast is specified, otherwise the default is 6000
under -O2 and 9000 under -O3.
-OPT:roundoff,ro=(n)
Specifies the level of acceptable departure from source
language floating-point, round-off, and overflow semantics. n
can be one of the following:
0 Inhibits optimizations that might affect the
floating-point behavior. This is the default when
optimization levels -O0, -O1, and -O2 are in effect.
1 Allows simple transformations that might cause limited
round-off or overflow differences. Compounding such
transformations could have more extensive effects.
This is the default level when -O3 is in effect.
2 Allows more extensive transformations, such as the
reordering of reduction loops. This is the default
level when -Ofast is specified.
3 Enables any mathematically valid transformation.
-OPT:unroll_analysis=(ON|OFF)
The default value of ON lets the compiler analyze the
content of the loop to determine the best unrolling
parameters, instead of strictly adhering to the
-OPT:unroll_times_max and -OPT:unroll_size parameters.
-OPT:unroll_times_max,unroll_times=(n)
Unroll inner loops by a maximum of n. The default is 4.
-OPT:unroll_size=(n)
Sets the ceiling of maximum number of instructions for an
unrolled inner loop. If n = 0, the ceiling is disregarded.
-static
Suppresses dynamic linking at run-time for shared libraries;
uses static linking instead.
-TENV:X=(0|1|2|3|4)
Specify the level of enabled exceptions that will be assumed
for purposes of performing speculative code motion (default
is 1 at all optimization levels). In general, an instruction
will not be speculated (i.e. moved above a branch by the
optimizer) unless any exceptions it might cause are disabled
by this option. At level 0, no speculative code motion may
be performed. At level 1, safe speculative code motion may
be performed, with IEEE-754 underflow and inexact exceptions
disabled. At level 2, all IEEE-754 exceptions are disabled
except divide by zero. At level 3, all IEEE-754 exceptions
are disabled including divide by zero. At level 4, memory
exceptions may be disabled or ignored.
-TENV:frame_pointer=(ON|OFF)
Default is ON for C++ and OFF otherwise.
Local variables in the function stack frame are addressed via
the frame pointer register. Ordinarily, the compiler will
replace this use of frame pointer by addressing local variables
via the stack pointer when it determines that the stack pointer
is fixed throughout the function invocation. This frees up the
frame pointer for other purposes. Turning this flag on forces
the compiler to use the frame pointer to address local variables.
This flag defaults to on for C++ because the exception handling
mechanism relies on the frame pointer register being used to
address local variables. This flag can be turned off for C++
for programs that do not throw exceptions.
-Wl,-x
Passes the -x option to the linker. With this flag set, the
linker will not preserve local (non-global) symbols in the output
symbol table. The linker enters external and static symbols
only. This option conserves space in the output file. This is
OFF by default.
-WOPT:mem_opnds=(ON|OFF)
ON makes the scalar optimizer preserve any memory operands of
arithmetic operations so as to promote subsumption of memory
loads into the operands of arithmetic operations. The default
is OFF.
-WOPT:retype_expr=(ON|OFF)
ON enables the optimization in the compiler that converts 64-bit
address computation to use 32-bit arithmetic as much as
possible. The default is OFF.
-WOPT:val=(0|1|2)
Controls the number of times the value-numbering optimization is
performed in the global optimizer, with the default being 1.
This optimization tries to recognize expressions that will
compute identical run-time values and changes the program to avoid
re-computing them.
----------------------------------------------------------------------------
Flags for gcc 3.5 ssa (from Red Hat Enterprise Linux WS 3 (AMD64))
SuSE optional gcc 3.3 (from SLES8 SP3)
----------------------------------------------------------------------------
-O0
Do not optimize. This is the default.
-O
-O1
Optimize. Optimizing compilation takes somewhat more time, and a lot
more memory for a large function.
With `-O', the compiler tries to reduce code size and execution time,
without performing any optimizations that take a great deal of
compilation time.
`-O' turns on the following optimization flags:
-fdefer-pop
-fmerge-constants
-fthread-jumps
-floop-optimize
-fcrossjumping
-fif-conversion
-fif-conversion2
-fdelayed-branch
-fguess-branch-probability
-fcprop-registers
`-O' also turns on `-fomit-frame-pointer' on machines where doing so
does not interfere with debugging.
-O2
Optimize even more. GCC performs nearly all supported optimizations
that do not involve a space-speed tradeoff. The compiler does not
perform loop unrolling or function inlining when you specify `-O2'.
As compared to `-O', this option increases both compilation time and
the performance of the generated code.
`-O2' turns on all optimization flags specified by `-O'. It also
turns on the following optimization flags:
-fforce-mem
-foptimize-sibling-calls
-fstrength-reduce
-fcse-follow-jumps -fcse-skip-blocks
-frerun-cse-after-loop -frerun-loop-opt
-fgcse -fgcse-lm -fgcse-sm
-fdelete-null-pointer-checks
-fexpensive-optimizations
-fregmove
-fschedule-insns -fschedule-insns2
-fsched-interblock -fsched-spec
-fcaller-saves
-fpeephole2
-freorder-blocks -freorder-functions
-fstrict-aliasing
-falign-functions -falign-jumps
-falign-loops -falign-labels
Please note the warning under `-fgcse' about invoking `-O2' on
programs that use computed gotos.
-O3
Optimize yet more. `-O3' turns on all optimizations specified by
`-O2' and also turns on the `-finline-functions', `-fweb',
`-funit-at-time', `-ftracer', `-funswitch-loops' and
`-frename-registers' options.
-funroll-all-loops
Unroll all loops, even if their number of iterations is uncertain
when the loop is entered. This usually makes programs run more
slowly. `-funroll-all-loops' implies the same options as
`-funroll-loops'
-fprofile-arcs/-fbranch-probabilities
-fprofile-arcs
Instrument "arcs" during compilation to generate coverage data or for
profile-directed block ordering. During execution the program
records how many times each branch is executed and how many times it
is taken. When the compiled program exits it saves this data to a
file called `AUXNAME.da' for each source file. AUXNAME is generated
from the name of the output file, if explicitly specified and it is
not the final executable, otherwise it is the basename of the source
file. In both cases any suffix is removed (e.g. `foo.da' for input
file `dir/foo.c', or `dir/foo.da' for output file specified as `-o
dir/foo.o').
For profile-directed block ordering, compile the program with
`-fprofile-arcs' plus optimization and code generation options,
generate the arc profile information by running the program on a
selected workload, and then compile the program again with the same
optimization and code generation options plus
`-fbranch-probabilities' (*note Options that Control Optimization:
Optimize Options.).
With `-fprofile-arcs', for each function of your program GCC creates
a program flow graph, then finds a spanning tree for the graph. Only
arcs that are not on the spanning tree have to be instrumented: the
compiler adds code to count the number of times that these arcs are
executed. When an arc is the only exit or only entrance to a block,
the instrumentation code can be added to the block; otherwise, a new
basic block must be created to hold the instrumentation code.
-ffast-math
Sets `-fno-math-errno', `-funsafe-math-optimizations',
`-fno-trapping-math', `-ffinite-math-only' and
`-fno-signaling-nans'.
This option causes the preprocessor macro `__FAST_MATH__' to be
defined.
This option should never be turned on by any `-O' option since it can
result in incorrect output for programs which depend on an exact
implementation of IEEE or ISO rules/specifications for math
functions.
-fno-math-errno
Do not set ERRNO after calling math functions that are executed with
a single instruction, e.g., sqrt. A program that relies on IEEE
exceptions for math error handling may want to use this flag for
speed while maintaining IEEE arithmetic compatibility.
This option should never be turned on by any `-O' option since it can
result in incorrect output for programs which depend on an exact
implementation of IEEE or ISO rules/specifications for math
functions.
The default is `-fmath-errno'.
-funsafe-math-optimizations
Allow optimizations for floating-point arithmetic that (a) assume
that arguments and results are valid and (b) may violate IEEE or ANSI
standards. When used at link-time, it may include libraries or
startup files that change the default FPU control word or other
similar optimizations.
This option should never be turned on by any `-O' option since it can
result in incorrect output for programs which depend on an exact
implementation of IEEE or ISO rules/specifications for math
functions.
The default is `-fno-unsafe-math-optimizations'.
-ffinite-math-only
Allow optimizations for floating-point arithmetic that assume that
arguments and results are not NaNs or +-Infs.
This option should never be turned on by any `-O' option since it can
result in incorrect output for programs which depend on an exact
implementation of IEEE or ISO rules/specifications.
The default is `-fno-finite-math-only'.
-fno-trapping-math
Compile code assuming that floating-point operations cannot generate
user-visible traps. These traps include division by zero, overflow,
underflow, inexact result and invalid operation. This option implies
`-fno-signaling-nans'. Setting this option may allow faster code if
one relies on "non-stop" IEEE arithmetic, for example.
This option should never be turned on by any `-O' option since it can
result in incorrect output for programs which depend on an exact
implementation of IEEE or ISO rules/specifications for math
functions.
The default is `-ftrapping-math'.
-fsignaling-nans
Compile code assuming that IEEE signaling NaNs may generate
user-visible traps during floating-point operations. Setting this
option disables optimizations that may change the number of
exceptions visible with signaling NaNs. This option implies
`-ftrapping-math'.
This option causes the preprocessor macro `__SUPPORT_SNAN__' to be
defined.
The default is `-fno-signaling-nans'.
This option is experimental and does not currently guarantee to
disable all GCC optimizations that affect signaling NaN behavior.
-m32
-m64
These `-m' switches are supported in addition to the above on AMD
x86-64 processors in 64-bit environments.
Generate code for a 32-bit or 64-bit environment. The 32-bit
environment sets int, long and pointer to 32 bits and generates code
that runs on any i386 system. The 64-bit environment sets int to 32
bits and long and pointer to 64 bits and generates code for AMD's
x86-64 architecture.
-msse2
-mno-sse
-mno-sse2
These switches enable or disable the use of built-in functions that
allow direct access to the MMX, SSE and 3Dnow extensions of the
instruction set.
-fno-defer-pop
Always pop the arguments to each function call as soon as that
function returns. For machines which must pop arguments after a
function call, the compiler normally lets arguments accumulate on the
stack for several function calls and pops them all at once.
Disabled at levels `-O', `-O2', `-O3', `-Os'.
-fmerge-constants
Attempt to merge identical constants (string constants and floating
point constants) across compilation units.
This option is the default for optimized compilation if the assembler
and linker support it. Use `-fno-merge-constants' to inhibit this
behavior.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fthread-jumps
Perform optimizations where we check to see if a jump branches to a
location where another comparison subsumed by the first is found. If
so, the first branch is redirected to either the destination of the
second branch or a point immediately following it, depending on
whether the condition is known to be true or false.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-floop-optimize
Perform loop optimizations: move constant expressions out of loops,
simplify exit test conditions and optionally do strength-reduction
and loop unrolling as well.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fcrossjumping
Perform cross-jumping transformation. This transformation unifies
equivalent code and save code size. The resulting code may or may not
perform better than without cross-jumping.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fif-conversion
Attempt to transform conditional jumps into branch-less equivalents.
This include use of conditional moves, min, max, set flags and abs
instructions, and some tricks doable by standard arithmetics. The
use of conditional execution on chips where it is available is
controlled by `if-conversion2'.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fif-conversion2
Use conditional execution (where available) to transform conditional
jumps into branch-less equivalents.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fdelayed-branch
If supported for the target machine, attempt to reorder instructions
to exploit instruction slots available after delayed branch
instructions.
Enabled at levels `-O', `-O2', `-O3', `-Os'.
-fguess-branch-probability
Do not guess branch probabilities using a randomized model.
Sometimes gcc will opt to use a randomized model to guess branch
probabilities, when none are available from either profiling feedback
(`-fprofile-arcs') or `__builtin_expect'. This means that different
runs of the compiler on the same program may produce different object
code.
In a hard real-time system, people don't want different runs of the
compiler to produce code that has different behavior; minimizing
non-determinism is of paramount import. This switch allows users to
reduce non-determinism, possibly at the expense of inferior
optimization.
The default is `-fguess-branch-probability' at levels `-O', `-O2',
`-O3', `-Os'.
-fcprop-registers
After register allocation and post-register allocation instruction
splitting, we perform a copy-propagation pass to try to reduce
scheduling dependencies and occasionally eliminate the copy.
Disabled at levels `-O', `-O2', `-O3', `-Os'.
-fforce-mem
Force memory operands to be copied into registers before doing
arithmetic on them. This produces better code by making all memory
references potential common subexpressions. When they are not common
subexpressions, instruction combination should eliminate the separate
register-load.
Enabled at levels `-O2', `-O3', `-Os'.
-foptimize-sibling-calls
Optimize sibling and tail recursive calls.
Enabled at levels `-O2', `-O3', `-Os'.
-fstrength-reduce
Perform the optimizations of loop strength reduction and elimination
of iteration variables.
Enabled at levels `-O2', `-O3', `-Os'.
-fcse-follow-jumps
In common subexpression elimination, scan through jump instructions
when the target of the jump is not reached by any other path. For
example, when CSE encounters an `if' statement with an `else' clause,
CSE will follow the jump when the condition tested is false.
Enabled at levels `-O2', `-O3', `-Os'.
-fcse-skip-blocks
This is similar to `-fcse-follow-jumps', but causes CSE to follow
jumps which conditionally skip over blocks. When CSE encounters a
simple `if' statement with no else clause, `-fcse-skip-blocks' causes
CSE to follow the jump around the body of the `if'.
Enabled at levels `-O2', `-O3', `-Os'.
-frerun-cse-after-loop
Re-run common subexpression elimination after loop optimizations has
been performed.
Enabled at levels `-O2', `-O3', `-Os'.
-frerun-loop-opt
Run the loop optimizer twice.
Enabled at levels `-O2', `-O3', `-Os'.
-fgcse
Perform a global common subexpression elimination pass. This pass
also performs global constant and copy propagation.
_Note:_ When compiling a program using computed gotos, a GCC
extension, you may get better runtime performance if you disable the
global common subexpression elimination pass by adding `-fno-gcse' to
the command line.
Enabled at levels `-O2', `-O3', `-Os'.
-fgcse-lm
When `-fgcse-lm' is enabled, global common subexpression elimination
will attempt to move loads which are only killed by stores into
themselves. This allows a loop containing a load/store sequence to
be changed to a load outside the loop, and a copy/store within the
loop.
Enabled by default when gcse is enabled.
-fgcse-sm
When `-fgcse-sm' is enabled, A store motion pass is run after global
common subexpression elimination. This pass will attempt to move
stores out of loops. When used in conjunction with `-fgcse-lm',
loops containing a load/store sequence can be changed to a load
before the loop and a store after the loop.
Enabled by default when gcse is enabled.
-fdelete-null-pointer-checks
Use global dataflow analysis to identify and eliminate useless checks
for null pointers. The compiler assumes that dereferencing a null
pointer would have halted the program. If a pointer is checked after
it has already been dereferenced, it cannot be null.
In some environments, this assumption is not true, and programs can
safely dereference null pointers. Use
`-fno-delete-null-pointer-checks' to disable this optimization for
programs which depend on that behavior.
Enabled at levels `-O2', `-O3', `-Os'.
-fexpensive-optimizations
Perform a number of minor optimizations that are relatively
expensive.
Enabled at levels `-O2', `-O3', `-Os'.
-fregmove
Attempt to reassign register numbers in move instructions and as
operands of other simple instructions in order to maximize the amount
of register tying. This is especially helpful on machines with
two-operand instructions.
Note `-fregmove' and `-foptimize-register-move' are the same
optimization.
Enabled at levels `-O2', `-O3', `-Os'.
-fschedule-insns
If supported for the target machine, attempt to reorder instructions
to eliminate execution stalls due to required data being
unavailable. This helps machines that have slow floating point or
memory load instructions by allowing other instructions to be issued
until the result of the load or floating point instruction is
required.
Enabled at levels `-O2', `-O3', `-Os'.
-fschedule-insns2
Similar to `-fschedule-insns', but requests an additional pass of
instruction scheduling after register allocation has been done. This
is especially useful on machines with a relatively small number of
registers and where memory load instructions take more than one
cycle.
Enabled at levels `-O2', `-O3', `-Os'.
-fsched-interblock
-fno-sched-interblock
Don't schedule instructions across basic blocks. This is normally
enabled by default when scheduling before register allocation, i.e.
with `-fschedule-insns' or at `-O2' or higher.
-fsched-spec
-fno-sched-spec
Don't allow speculative motion of non-load instructions. This is
normally enabled by default when scheduling before register
allocation, i.e. with `-fschedule-insns' or at `-O2' or higher.
-fcaller-saves
Enable values to be allocated in registers that will be clobbered by
function calls, by emitting extra instructions to save and restore
the registers around such calls. Such allocation is done only when
it seems to result in better code than would otherwise be produced.
This option is always enabled by default on certain machines, usually
those which have no call-preserved registers to use instead.
Enabled at levels `-O2', `-O3', `-Os'.
-fpeephole2
-fno-peephole
-fno-peephole2
Disable any machine-specific peephole optimizations. The difference
between `-fno-peephole' and `-fno-peephole2' is in how they are
implemented in the compiler; some targets use one, some use the
other, a few use both.
`-fpeephole' is enabled by default. `-fpeephole2' enabled at
levels `-O2', `-O3', `-Os'.
-freorder-blocks
Reorder basic blocks in the compiled function in order to reduce
number of taken branches and improve code locality.
Enabled at levels `-O2', `-O3', `-Os'.
-freorder-functions
Reorder basic blocks in the compiled function in order to reduce
number of taken branches and improve code locality. This is
implemented by using special subsections `text.hot' for most
frequently executed functions and `text.unlikely' for unlikely
executed functions. Reordering is done by the linker so object file
format must support named sections and linker must place them in a
reasonable way.
Also profile feedback must be available in to make this option
effective. See `-fprofile-arcs' for details.
Enabled at levels `-O2', `-O3', `-Os'.
-fstrict-aliasing
Allows the compiler to assume the strictest aliasing rules applicable
to the language being compiled. For C (and C++), this activates
optimizations based on the type of expressions. In particular, an
object of one type is assumed never to reside at the same address as
an object of a different type, unless the types are almost the same.
For example, an `unsigned int' can alias an `int', but not a `void*'
or a `double'. A character type may alias any other type.
Pay special attention to code like this:
union a_union {
int i;
double d;
};
int f() {
a_union t;
t.d = 3.0;
return t.i;
}
The practice of reading from a different union member than the one
most recently written to (called "type-punning") is common. Even
with `-fstrict-aliasing', type-punning is allowed, provided the
memory is accessed through the union type. So, the code above will
work as expected. However, this code might not:
int f() {
a_union t;
int* ip;
t.d = 3.0;
ip = &t.i;
return *ip;
}
Every language that wishes to perform language-specific alias
analysis should define a function that computes, given an `tree'
node, an alias set for the node. Nodes in different alias sets are
not allowed to alias. For an example, see the C front-end function
`c_get_alias_set'.
Enabled at levels `-O2', `-O3', `-Os'.
-falign-functions
-falign-functions=N
Align the start of functions to the next power-of-two greater than N,
skipping up to N bytes. For instance, `-falign-functions=32' aligns
functions to the next 32-byte boundary, but `-falign-functions=24'
would align to the next 32-byte boundary only if this can be done by
skipping 23 bytes or less.
`-fno-align-functions' and `-falign-functions=1' are equivalent and
mean that functions will not be aligned.
Some assemblers only support this flag when N is a power of two; in
that case, it is rounded up.
If N is not specified, use a machine-dependent default.
Enabled at levels `-O2', `-O3'.
-falign-jumps
-falign-jumps=N
Align branch targets to a power-of-two boundary, for branch targets
where the targets can only be reached by jumping, skipping up to N
bytes like `-falign-functions'. In this case, no dummy operations
need be executed.
If N is not specified, use a machine-dependent default.
Enabled at levels `-O2', `-O3'.
-falign-loops
-falign-loops=N
Align loops to a power-of-two boundary, skipping up to N bytes like
`-falign-functions'. The hope is that the loop will be executed many
times, which will make up for any execution of the dummy operations.
If N is not specified, use a machine-dependent default.
Enabled at levels `-O2', `-O3'.
-falign-labels
-falign-labels=N
Align all branch targets to a power-of-two boundary, skipping up to N
bytes like `-falign-functions'. This option can easily make code
slower, because it must insert dummy operations for when the branch
target is reached in the usual flow of the code.
If `-falign-loops' or `-falign-jumps' are applicable and are
greater than this value, then their values are used instead.
If N is not specified, use a machine-dependent default which is very
likely to be `1', meaning no alignment.
Enabled at levels `-O2', `-O3'.
-finline-limit=N
By default, gcc limits the size of functions that can be inlined.
This flag allows the control of this limit for functions that are
explicitly marked as inline (i.e., marked with the inline keyword
or defined within the class definition in c++). N is the size of
functions that can be inlined in number of pseudo instructions
(not counting parameter handling). The default value of N is 600.
Increasing this value can result in more inlined code at the cost
of compilation time and memory consumption. Decreasing usually
makes the compilation faster and less code will be inlined (which
presumably means slower programs). This option is particularly
useful for programs that use inlining heavily such as those based
on recursive templates with C++.
Inlining is actually controlled by a number of parameters, which
may be specified individually by using `--param NAME=VALUE'. The
`-finline-limit=N' option sets some of these parameters as follows:
max-inline-insns
is set to N.
max-inline-insns-single
is set to N/2.
max-inline-insns-single-auto
is set to N/2.
min-inline-insns
is set to 130 or N/4, whichever is smaller.
max-inline-insns-rtl
is set to N.
Using `-finline-limit=600' thus results in the default settings for
these parameters. See below for a documentation of the individual
parameters controlling inlining.
_Note:_ pseudo instruction represents, in this particular context, an
abstract measurement of function's size. In no way, it represents a
count of assembly instructions and as such its exact meaning might
change from one release to an another.
-freduce-all-givs
Forces all general-induction variables in loops to be
strength-reduced.
_Note:_ When compiling programs written in Fortran,
`-fmove-all-movables' and `-freduce-all-givs' are enabled by default
when you use the optimizer.
These options may generate better or worse code; results are highly
dependent on the structure of loops within the source code.
-fprefetch-loop-arrays
If supported by the target machine, generate instructions to prefetch
memory to improve the performance of loops that access large arrays.
Disabled at level `-Os'.
rm -f *.da *.life analyz_prbrob.out
Remove any profile feedback information from previous runs.
----------------------------------------------------------------------------
Portability flags used with gcc 3.5 ssa compiler
----------------------------------------------------------------------------
-DSPEC_CPU2000_LP64
Used to make longs and pointers 64 bit.
-DHAS_ERRLIST
Tells that the system provides the "sys_nerr" and "sys_errlist[]"
variables in 252.eon.