nicolas/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

15
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
View File

@@ -5006,7 +5006,7 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
break;
}
case bitc::FUNC_CODE_INST_CALL: {
// CALL: [paramattrs, cc, fnty, fnid, arg0, arg1...]
// CALL: [paramattrs, cc, fmf, fnty, fnid, arg0, arg1...]
if (Record.size() < 3)
return error("Invalid record");
@@ -5014,6 +5014,13 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
AttributeSet PAL = getAttributes(Record[OpNum++]);
unsigned CCInfo = Record[OpNum++];
FastMathFlags FMF;
if ((CCInfo >> bitc::CALL_FMF) & 1) {
FMF = getDecodedFastMathFlags(Record[OpNum++]);
if (!FMF.any())
return error("Fast math flags indicator set for call with no FMF");
}
FunctionType *FTy = nullptr;
if (CCInfo >> bitc::CALL_EXPLICIT_TYPE & 1 &&
!(FTy = dyn_cast<FunctionType>(getTypeByID(Record[OpNum++]))))
@@ -5075,6 +5082,12 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
TCK = CallInst::TCK_NoTail;
cast<CallInst>(I)->setTailCallKind(TCK);
cast<CallInst>(I)->setAttributes(PAL);
if (FMF.any()) {
if (!isa<FPMathOperator>(I))
return error("Fast-math-flags specified for call without "
"floating-point scalar or vector return type");
I->setFastMathFlags(FMF);
}
break;
}
case bitc::FUNC_CODE_INST_VAARG: { // VAARG: [valistty, valist, instty]