change an assert when generating fmuladd to an ordinary 'if' check (PR25719)

We don't want to generate fmuladd if there's a use of the fmul expression, but this shouldn't be an assert.

The test case is derived from the commit message for r253337:
http://reviews.llvm.org/rL253337

That commit reverted r253269:
http://reviews.llvm.org/rL253269

...but the bug exists independently of the default fp-contract setting. It just became easier to hit with that change.

PR25719:
https://llvm.org/bugs/show_bug.cgi?id=25719

Differential Revision: http://reviews.llvm.org/D15165

llvm-svn: 254573

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/test/CodeGen/fp-contract-pragma.cpp b/clang/test/CodeGen/fp-contract-pragma.cpp
index 86e236e4db5..1ea974f5fef 100644
--- a/clang/test/CodeGen/fp-contract-pragma.cpp
+++ b/clang/test/CodeGen/fp-contract-pragma.cpp
@@ -62,3 +62,15 @@ float fp_contract_6(float a, float b, float c) {
   return a * b + c;
 }
 
+// If the multiply has multiple uses, don't produce fmuladd.
+// This used to assert (PR25719):
+// https://llvm.org/bugs/show_bug.cgi?id=25719
+
+float fp_contract_7(float a, float b, float c) {
+// CHECK: _Z13fp_contract_7fff
+// CHECK:  %mul = fmul float %b, 2.000000e+00
+// CHECK-NEXT: fsub float %mul, %c
+  #pragma STDC FP_CONTRACT ON
+  return (a = 2 * b) - c;
+}
+