[CodeGen] Teach LLVM how to lower @llvm.{min,max}num to {MIN,MAX}NAN

The behavior of {MIN,MAX}NAN differs from that of {MIN,MAX}NUM when only
one of the inputs is NaN: -NUM will return the non-NaN argument while
-NAN would return NaN.

It is desirable to lower to @llvm.{min,max}num to -NAN if they don't
have a native instruction for -NUM.  Notably, ARMv7 NEON's vmin has the
-NAN semantics.

N.B.  Of course, it is only safe to do this if the intrinsic call is
marked nnan.

llvm-svn: 266279

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/vminmax.ll b/llvm/test/CodeGen/ARM/vminmax.ll
index 011bfd7ff88..e4f30faa917 100644
--- a/llvm/test/CodeGen/ARM/vminmax.ll
+++ b/llvm/test/CodeGen/ARM/vminmax.ll
@@ -291,3 +291,20 @@ declare <8 x i16> @llvm.arm.neon.vmaxu.v8i16(<8 x i16>, <8 x i16>) nounwind read
 declare <4 x i32> @llvm.arm.neon.vmaxu.v4i32(<4 x i32>, <4 x i32>) nounwind readnone
 
 declare <4 x float> @llvm.arm.neon.vmaxs.v4f32(<4 x float>, <4 x float>) nounwind readnone
+
+declare float @llvm.maxnum.f32(float %a, float %b)
+declare float @llvm.minnum.f32(float %a, float %b)
+
+define float @maxnum(float %a, float %b) {
+;CHECK-LABEL: maxnum:
+;CHECK: vmax.f32
+  %r = call nnan float @llvm.maxnum.f32(float %a, float %b)
+  ret float %r
+}
+
+define float @minnum(float %a, float %b) {
+;CHECK-LABEL: minnum:
+;CHECK: vmin.f32
+  %r = call nnan float @llvm.minnum.f32(float %a, float %b)
+  ret float %r
+}