New virtual registers created for spill intervals should inherit allocation hints from the original register.
This helps us avoid silly copies when rematting values that are copied to a physical register:
leaq _.str44(%rip), %rcx
movq %rcx, %rsi
call _strcmp
becomes:
leaq _.str44(%rip), %rsi
call _strcmp
The coalescer will not touch the movq because that would tie down the physical register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90163 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 4412c1b..24adf36 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1095,6 +1095,12 @@
NewVReg = mri_->createVirtualRegister(rc);
vrm.grow();
CreatedNewVReg = true;
+
+ // The new virtual register should get the same allocation hints as the
+ // old one.
+ std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(Reg);
+ if (Hint.first || Hint.second)
+ mri_->setRegAllocationHint(NewVReg, Hint.first, Hint.second);
}
if (!TryFold)