Red Hat ENTERPRISE LINUX 3 - USING GCC Using Instructions page 64

58
-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
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
on "non-stop" IEEE arithmetic, for example.
This option should never be turned on by any
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
This option causes the preprocessor macro
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.
-fsingle-precision-constant
Treat floating point constant as single precision constant instead of implicitly converting it to
double precision constant.
The following options control optimizations that may improve performance, but are not enabled by
any options. This section includes experimental options that may produce broken code.
-O
-fbranch-probabilities
After running a program compiled with
Options for Debugging Your Program or GCC), you can compile it a second time using
-fbranch-probabilities
branch was taken. When the program compiled with
execution counts to a file called
data file is very dependent on the structure of the generated code, so you must use the same
source code and the same optimization options for both compilations.
With
-fbranch-probabilities
. These can be used to improve optimization. Currently, they are only used in one
CALL_INSN
place: in
reorg.c
values are used to exactly determine which path is taken more often.
-fnew-ra
Use a graph coloring register allocator. Currently this option is meant for testing, so we are
interested to hear about miscompilations with
.
, to improve optimizations based on the number of times each
sourcename
, GCC puts a
, instead of guessing which path a branch is mostly to take, the
Chapter 4. GCC Command Options
option since it can result in incorrect output for
-O
.
. Setting this option may allow faster code if one relies
option since it can result in incorrect output
-O
__SUPPORT_SNAN__
.
-fprofile-arcs
-fprofile-arcs
for each source file The information in this
.da
REG_BR_PROB
.
-fnew-ra
.
-ftrapping-math
to be defined.
(refer to Section 4.9
exits it saves arc
note on each
JUMP_INSN
REG_BR_PROB
and