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, 21 insertions, 1 deletions

diff --git a/llvm/unittests/IR/IRBuilderTest.cpp b/llvm/unittests/IR/IRBuilderTest.cpp
index 0c602ed2b78..e0da018d7bf 100644
--- a/llvm/unittests/IR/IRBuilderTest.cpp
+++ b/llvm/unittests/IR/IRBuilderTest.cpp
@@ -131,7 +131,7 @@ TEST_F(IRBuilderTest, GetIntTy) {
 TEST_F(IRBuilderTest, FastMathFlags) {
   IRBuilder<> Builder(BB);
   Value *F, *FC;
-  Instruction *FDiv, *FAdd, *FCmp;
+  Instruction *FDiv, *FAdd, *FCmp, *FCall;
 
   F = Builder.CreateLoad(GV);
   F = Builder.CreateFAdd(F, F);
@@ -207,6 +207,26 @@ TEST_F(IRBuilderTest, FastMathFlags) {
   EXPECT_TRUE(FCmp->hasAllowReciprocal());
 
   Builder.clearFastMathFlags();
+ 
+  // Test a call with FMF.
+  auto CalleeTy = FunctionType::get(Type::getFloatTy(Ctx),
+                                    /*isVarArg=*/false);
+  auto Callee =
+      Function::Create(CalleeTy, Function::ExternalLinkage, "", M.get());
+
+  FCall = Builder.CreateCall(Callee, None);
+  EXPECT_FALSE(FCall->hasNoNaNs());
+
+  FMF.clear();
+  FMF.setNoNaNs();
+  Builder.SetFastMathFlags(FMF);
+
+  FCall = Builder.CreateCall(Callee, None);
+  EXPECT_TRUE(Builder.getFastMathFlags().any());
+  EXPECT_TRUE(Builder.getFastMathFlags().NoNaNs);
+  EXPECT_TRUE(FCall->hasNoNaNs());
+
+  Builder.clearFastMathFlags();
 
   // To test a copy, make sure that a '0' and a '1' change state. 
   F = Builder.CreateFDiv(F, F);