Fast-math test for SimplifyInstruction: fold multiply by 0

Applied the patch, rather than committing it.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168656 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstSimplify/fast-math.ll

@@ -0,0 +1,35 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+;; x * 0 ==> 0 when no-nans and no-signed-zero
+; CHECK: mul_zero_1
+define float @mul_zero_1(float %a) {
+  %b = fmul nsz nnan float %a, 0.0
+; CHECK: ret float 0.0
+  ret float %b
+}
+; CHECK: mul_zero_2
+define float @mul_zero_2(float %a) {
+  %b = fmul fast float 0.0, %a
+; CHECK: ret float 0.0
+  ret float %b
+}
+
+;; x * 0 =/=> 0 when there could be nans or -0
+; CHECK: no_mul_zero_1
+define float @no_mul_zero_1(float %a) {
+  %b = fmul nsz float %a, 0.0
+; CHECK: ret float %b
+  ret float %b
+}
+; CHECK: no_mul_zero_2
+define float @no_mul_zero_2(float %a) {
+  %b = fmul nnan float %a, 0.0
+; CHECK: ret float %b
+  ret float %b
+}
+; CHECK: no_mul_zero_3
+define float @no_mul_zero_3(float %a) {
+  %b = fmul float %a, 0.0
+; CHECK: ret float %b
+  ret float %b
+}