Fix a minor bug in two-address pass. It was missing a commute opportunity.
regB = move RCX
regA = op regB, regC
RAX = move regA
where both regB and regC are killed. If regB is constrainted to non-compatible
physical registers but regC is not constrainted at all, then it's better to
commute the instruction.
movl %edi, %eax
shlq $32, %rcx
leaq (%rcx,%rax), %rax
=>
movl %edi, %eax
shlq $32, %rcx
orq %rcx, %rax
rdar://8762995
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121793 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index f4cca25..60086ce 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -554,7 +554,8 @@
unsigned ToRegB = getMappedReg(regB, DstRegMap);
unsigned ToRegC = getMappedReg(regC, DstRegMap);
if (!regsAreCompatible(FromRegB, ToRegB, TRI) &&
- (regsAreCompatible(FromRegB, ToRegC, TRI) ||
+ ((!FromRegC && !ToRegC) ||
+ regsAreCompatible(FromRegB, ToRegC, TRI) ||
regsAreCompatible(FromRegC, ToRegB, TRI)))
return true;