Don't do (x - (y - z)) --> (x + (z - y)) on floating-point types, because

it may round differently. This fixes PR4374.

llvm-svn: 73243

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/fsub-fsub.ll b/llvm/test/Transforms/InstCombine/fsub-fsub.ll
new file mode 100644
index 00000000000..ab70479204b
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/fsub-fsub.ll
@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep fsub | count 2
+; PR4374
+
+define float @func(float %a, float %b) nounwind {
+        %tmp3 = fsub float %a, %b
+        %tmp4 = fsub float -0.000000e+00, %tmp3
+        ret float %tmp4
+}