Correctly handle <undef> tied uses when rewriting after a split.
This fixes PR10463. A two-address instruction with an <undef> use
operand was incorrectly rewritten so the def and use no longer used the
same register, violating the tie constraint.
Fix this by always rewriting <undef> operands with the register a def
operand would use.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135885 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index d607e37..46a43d8 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -938,15 +938,11 @@
continue;
}
- // <undef> operands don't really read the register, so just assign them to
- // the complement.
- if (MO.isUse() && MO.isUndef()) {
- MO.setReg(Edit->get(0)->reg);
- continue;
- }
-
+ // <undef> operands don't really read the register, so it doesn't matter
+ // which register we choose. When the use operand is tied to a def, we must
+ // use the same register as the def, so just do that always.
SlotIndex Idx = LIS.getInstructionIndex(MI);
- if (MO.isDef())
+ if (MO.isDef() || MO.isUndef())
Idx = MO.isEarlyClobber() ? Idx.getUseIndex() : Idx.getDefIndex();
// Rewrite to the mapped register at Idx.