Red Hat ENTERPRISE LINUX 4 Manual page 73

Chapter 4. GCC Command Options
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.
-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
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
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
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
-frounding-math
Disable transformations and optimizations that assume default floating point rounding behavior.
This is round-to-zero for all floating point to integer conversions, and round-to-nearest for all
other arithmetic truncations. This option should be specified for programs that change the FP
rounding mode dynamically, or that may be executed with a non-default rounding mode. This
option disables constant folding of floating point expressions at compile-time (which may be
affected by rounding mode) and arithmetic transformations that are unsafe in the presence of
sign-dependent rounding modes.
The default is
-fno-rounding-math
This option is experimental and does not currently guarantee to disable all GCC optimizations
that are affected by rounding mode. Future versions of GCC may provide finer control of this
option since it can result in incorrect output
-O
option since it can result in incorrect output
-O
.
option since it can result in incorrect output
-O
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
.
.
.
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