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add fast-math-flags to 'call' instructions (PR21290)

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This patch adds optional fast-math-flags (the same that apply to fmul/fadd/fsub/fdiv/frem/fcmp)
to call instructions in IR. Follow-up patches would use these flags in LibCallSimplifier, add 
support to clang, and extend FMF to the DAG for calls.

Motivating example:

%y = fmul fast float %x, %x
%z = tail call float @sqrtf(float %y)

We'd like to be able to optimize sqrt(x*x) into fabs(x). We do this today using a function-wide
attribute for unsafe-math, but we really want to trigger on the instructions themselves:

%z = tail call fast float @sqrtf(float %y)

because in an LTO build it's possible that calls with fast semantics have been inlined into a
function with non-fast semantics.

The code changes and tests are based on the recent commits that added "notail":
http://reviews.llvm.org/rL252368

and added FMF to fcmp:
http://reviews.llvm.org/rL241901

Differential Revision: http://reviews.llvm.org/D14707

llvm-svn: 255555
This commit is contained in:
Sanjay Patel
2015-12-14 21:59:03 +00:00
parent 46642ffeeb
commit fa54acedd1
14 changed files with 129 additions and 45 deletions
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8
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
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@@ -2153,11 +2153,17 @@ static void WriteInstruction(const Instruction &I, unsigned InstID,
Code = bitc::FUNC_CODE_INST_CALL;
Vals.push_back(VE.getAttributeID(CI.getAttributes()));
unsigned Flags = GetOptimizationFlags(&I);
Vals.push_back(CI.getCallingConv() << bitc::CALL_CCONV |
unsigned(CI.isTailCall()) << bitc::CALL_TAIL |
unsigned(CI.isMustTailCall()) << bitc::CALL_MUSTTAIL |
1 << bitc::CALL_EXPLICIT_TYPE |
unsigned(CI.isNoTailCall()) << bitc::CALL_NOTAIL);
unsigned(CI.isNoTailCall()) << bitc::CALL_NOTAIL |
unsigned(Flags != 0) << bitc::CALL_FMF);
if (Flags != 0)
Vals.push_back(Flags);
Vals.push_back(VE.getTypeID(FTy));
PushValueAndType(CI.getCalledValue(), InstID, Vals, VE); // Callee