Fix PR11685 by implementing -ffast-math and its various friends in the
Clang driver. This involves a bunch of silly option parsing code to try
to carefully emulate GCC's options. Currently, this takes a conservative
approach, and unless all of the unsafe optimizations are enabled, none
of them are. The fine grained control doesn't seem particularly useful.
If it ever becomes useful, we can add that to LLVM first, and then
expose it here.
This also fixes a few tiny bugs in the flag management around
-fhonor-infinities and -fhonor-nans; the flags now form proper sets both
for enabling and disabling, with the last flag winning.
I've also implemented a moderately terrifying GCC feature where
a language change is also provided by the '-ffast-math' flag by defining
the __FAST_MATH__ preprocessor macro. This feature is tracked and
serialized in the frontend but it isn't used yet. A subsequent patch
will add the preprocessor macro and tests for it.
I've manually tested that codegen appears to respect this, but I've not
dug in enough to see if there is an easy way to test codegen options w/o
relying on the particulars of LLVM's optimizations.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147434 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index d275af2..ec6e03b 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -170,6 +170,9 @@
HelpText<"Allow optimization to assume there are no infinities.">;
def menable_no_nans : Flag<"-menable-no-nans">,
HelpText<"Allow optimization to assume there are no NaNs.">;
+def menable_unsafe_fp_math : Flag<"-menable-unsafe-fp-math">,
+ HelpText<"Allow unsafe floating-point math optimizations which may decrease "
+ "precision">;
def mfloat_abi : Separate<"-mfloat-abi">,
HelpText<"The float ABI to use">;
def mno_global_merge : Flag<"-mno-global-merge">,
@@ -482,6 +485,10 @@
HelpText<"Enable C++ exceptions">;
def fsjlj_exceptions : Flag<"-fsjlj-exceptions">,
HelpText<"Use SjLj style exceptions">;
+def ffast_math : Flag<"-ffast-math">,
+ HelpText<"Enable the *frontend*'s 'fast-math' mode. This has no effect on "
+ "optimizations, but provides a preprocessor macro __FAST_MATH__ the "
+ "same as GCC's -ffast-math flag.">;
def ffreestanding : Flag<"-ffreestanding">,
HelpText<"Assert that the compilation takes place in a freestanding environment">;
def fgnu_runtime : Flag<"-fgnu-runtime">,