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Fix a long-standing bug where Clang had a different default from GCC on 

Linux and other (non-Darwin) platforms and have it use -fmath-errno by
default (for better or worse).

Darwin has seen the light here and uses -fno-math-errno by default, this
patch preserves that.

If any maintainers for a non-Linux platform would also like to opt-in to
-fno-math-errno by default, I'm happy to add folks, but we're currently
getting buts and misleading comparisons with GCC due to this difference
in behavior on Linux at least.

llvm-svn: 155607
This commit is contained in:
Chandler Carruth 2012-04-26 02:10:51 +00:00
parent bc8c5b5d67
commit 3634c66b41
2 changed files with 17 additions and 11 deletions
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15
clang/lib/Driver/Tools.cpp
View File

@ -1617,16 +1617,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
A->getOption().getID() != options::OPT_fhonor_nans)
CmdArgs.push_back("-menable-no-nans");
// -fno-math-errno is default.
bool MathErrno = false;
// -fno-math-errno is default on Darwin. Other platforms, -fmath-errno is the
// default.
bool MathErrno = !getToolChain().getTriple().isOSDarwin();
if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
options::OPT_fmath_errno,
options::OPT_fno_math_errno)) {
if (A->getOption().getID() == options::OPT_fmath_errno) {
CmdArgs.push_back("-fmath-errno");
MathErrno = true;
}
}
options::OPT_fno_math_errno))
MathErrno = A->getOption().getID() == options::OPT_fmath_errno;
if (MathErrno)
CmdArgs.push_back("-fmath-errno");
// There are several flags which require disabling very specific
// optimizations. Any of these being disabled forces us to turn off the

13
clang/test/Driver/fast-math.c
View File

@ -19,8 +19,15 @@
// CHECK-MATH-ERRNO: "-cc1"
// CHECK-MATH-ERRNO: "-fmath-errno"
//
// RUN: %clang -### -fassociative-math -freciprocal-math -fno-signed-zeros \
// RUN: -fno-trapping-math -c %s 2>&1 \
// RUN: %clang -### -fmath-errno -fno-math-errno -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
// RUN: %clang -### -target i686-apple-darwin -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
// CHECK-NO-MATH-ERRNO: "-cc1"
// CHECK-NO-MATH-ERRNO-NOT: "-fmath-errno"
//
// RUN: %clang -### -fno-math-errno -fassociative-math -freciprocal-math \
// RUN: -fno-signed-zeros -fno-trapping-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-UNSAFE-MATH %s
// CHECK-UNSAFE-MATH: "-cc1"
// CHECK-UNSAFE-MATH: "-menable-unsafe-fp-math"
@ -36,7 +43,7 @@
// RUN: | FileCheck --check-prefix=CHECK-NO-INFS %s
// RUN: %clang -### -ffinite-math-only -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-NO-NANS %s
// RUN: %clang -### -funsafe-math-optimizations -c %s 2>&1 \
// RUN: %clang -### -funsafe-math-optimizations -fno-math-errno -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-UNSAFE-MATH %s
//
// One umbrella flag is *really* weird and also changes the semantics of the