Teach X86ISelLowering that the second result of X86ISD::UMUL is a flags

result.  This allows us to compile:

void *test12(long count) {
      return new int[count];
}

into:

test12:
	movl	$4, %ecx
	movq	%rdi, %rax
	mulq	%rcx
	movq	$-1, %rdi
	cmovnoq	%rax, %rdi
	jmp	__Znam                  ## TAILCALL

instead of:

test12:
	movl	$4, %ecx
	movq	%rdi, %rax
	mulq	%rcx
	seto	%cl
	testb	%cl, %cl
	movq	$-1, %rdi
	cmoveq	%rax, %rdi
	jmp	__Znam

Of course it would be even better if the regalloc inverted the cmov to 'cmovoq',
which would eliminate the need for the 'movq %rdi, %rax'.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120936 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 58b8cb1..6e1420c 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -7207,6 +7207,9 @@ static bool isX86LogicalCmp(SDValue Op) {
        Opc == X86ISD::AND))
     return true;
 
+  if (Op.getResNo() == 2 && Opc == X86ISD::UMUL)
+    return true;
+    
   return false;
 }