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, 0 deletions

diff --git a/llvm/test/Bitcode/compatibility.ll b/llvm/test/Bitcode/compatibility.ll
index de0fc137e53..465facc2a88 100644
--- a/llvm/test/Bitcode/compatibility.ll
+++ b/llvm/test/Bitcode/compatibility.ll
@@ -664,6 +664,28 @@ define void @fastmathflags(float %op1, float %op2) {
   ret void
 }
 
+; Check various fast math flags and floating-point types on calls.
+
+declare float @fmf1()
+declare double @fmf2()
+declare <4 x double> @fmf3()
+
+; CHECK-LABEL: fastMathFlagsForCalls(
+define void @fastMathFlagsForCalls(float %f, double %d1, <4 x double> %d2) {
+  %call.fast = call fast float @fmf1()
+  ; CHECK: %call.fast = call fast float @fmf1()
+
+  ; Throw in some other attributes to make sure those stay in the right places.
+
+  %call.nsz.arcp = notail call nsz arcp double @fmf2()
+  ; CHECK: %call.nsz.arcp = notail call nsz arcp double @fmf2()
+
+  %call.nnan.ninf = tail call nnan ninf fastcc <4 x double> @fmf3()
+  ; CHECK: %call.nnan.ninf = tail call nnan ninf fastcc <4 x double> @fmf3()
+
+  ret void
+}
+
 ;; Type System
 %opaquety = type opaque
 define void @typesystem() {