GlobalISel: expand mul-with-overflow into mul-hi on AArch64.

AArch64 has specific instructions to multiply two numbers at double the width
and produce the high part of the result. These can be used to implement LLVM's
mul.with.overflow instructions fairly simply. Helps with C++ operator new[].

llvm-svn: 294519

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
index ad0482ac7d5..32f9c5f80d0 100644
--- a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
@@ -64,7 +64,10 @@ AArch64LegalizerInfo::AArch64LegalizerInfo() {
     for (auto Ty : { s1, s8, s16, s32, s64 })
       setAction({BinOp, Ty}, Lower);
 
-  for (unsigned Op : {G_UADDE, G_USUBE, G_SADDO, G_SSUBO, G_SMULO, G_UMULO}) {
+  for (unsigned Op : {G_SMULO, G_UMULO})
+      setAction({Op, s64}, Lower);
+
+  for (unsigned Op : {G_UADDE, G_USUBE, G_SADDO, G_SSUBO, G_SMULH, G_UMULH}) {
     for (auto Ty : { s32, s64 })
       setAction({Op, Ty}, Legal);