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

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

1 files changed, 22 insertions, 12 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 3d43f81f49a..0b2880949f6 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -5603,14 +5603,14 @@ bool LLParser::ParseLandingPad(Instruction *&Inst, PerFunctionState &PFS) {
 }
 
 /// ParseCall
-///   ::= 'call' OptionalCallingConv OptionalAttrs Type Value
-///       ParameterList OptionalAttrs
-///   ::= 'tail' 'call' OptionalCallingConv OptionalAttrs Type Value
-///       ParameterList OptionalAttrs
-///   ::= 'musttail' 'call' OptionalCallingConv OptionalAttrs Type Value
-///       ParameterList OptionalAttrs
-///   ::= 'notail' 'call'  OptionalCallingConv OptionalAttrs Type Value
-///       ParameterList OptionalAttrs
+///   ::= 'call' OptionalFastMathFlags OptionalCallingConv
+///           OptionalAttrs Type Value ParameterList OptionalAttrs
+///   ::= 'tail' 'call' OptionalFastMathFlags OptionalCallingConv
+///           OptionalAttrs Type Value ParameterList OptionalAttrs
+///   ::= 'musttail' 'call' OptionalFastMathFlags OptionalCallingConv
+///           OptionalAttrs Type Value ParameterList OptionalAttrs
+///   ::= 'notail' 'call'  OptionalFastMathFlags OptionalCallingConv
+///           OptionalAttrs Type Value ParameterList OptionalAttrs
 bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
                          CallInst::TailCallKind TCK) {
   AttrBuilder RetAttrs, FnAttrs;
@@ -5624,10 +5624,14 @@ bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
   SmallVector<OperandBundleDef, 2> BundleList;
   LocTy CallLoc = Lex.getLoc();
 
-  if ((TCK != CallInst::TCK_None &&
-       ParseToken(lltok::kw_call,
-                  "expected 'tail call', 'musttail call', or 'notail call'")) ||
-      ParseOptionalCallingConv(CC) || ParseOptionalReturnAttrs(RetAttrs) ||
+  if (TCK != CallInst::TCK_None &&
+      ParseToken(lltok::kw_call,
+                 "expected 'tail call', 'musttail call', or 'notail call'"))
+    return true;
+
+  FastMathFlags FMF = EatFastMathFlagsIfPresent();
+
+  if (ParseOptionalCallingConv(CC) || ParseOptionalReturnAttrs(RetAttrs) ||
       ParseType(RetType, RetTypeLoc, true /*void allowed*/) ||
       ParseValID(CalleeID) ||
       ParseParameterList(ArgList, PFS, TCK == CallInst::TCK_MustTail,
@@ -5636,6 +5640,10 @@ bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
       ParseOptionalOperandBundles(BundleList, PFS))
     return true;
 
+  if (FMF.any() && !RetType->isFPOrFPVectorTy())
+    return Error(CallLoc, "fast-math-flags specified for call without "
+                          "floating-point scalar or vector return type");
+
   // If RetType is a non-function pointer type, then this is the short syntax
   // for the call, which means that RetType is just the return type.  Infer the
   // rest of the function argument types from the arguments that are present.
@@ -5708,6 +5716,8 @@ bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
   CallInst *CI = CallInst::Create(Ty, Callee, Args, BundleList);
   CI->setTailCallKind(TCK);
   CI->setCallingConv(CC);
+  if (FMF.any())
+    CI->setFastMathFlags(FMF);
   CI->setAttributes(PAL);
   ForwardRefAttrGroups[CI] = FwdRefAttrGrps;
   Inst = CI;