Handle IMPLICIT_DEF with isUndef operand marker, part 2. This patch moves the code to annotate machineoperands to LiveIntervalAnalysis. It also add markers for implicit_def that define physical registers. The rest, is just a lot of details.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74580 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index bbf1e24..be0b016 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -2029,8 +2029,12 @@
if (!TargetRegisterInfo::isVirtualRegister(VirtReg)) {
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
+ // Also check if it's copying from an "undef", if so, we can't
+ // eliminate this or else the undef marker is lost and it will
+ // confuses the scavenger. This is extremely rare.
unsigned Src, Dst, SrcSR, DstSR;
- if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst) {
+ if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst &&
+ !MI.findRegisterUseOperand(Src)->isUndef()) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
SmallVector<unsigned, 2> KillRegs;
@@ -2049,7 +2053,7 @@
Spills.disallowClobberPhysReg(VirtReg);
goto ProcessNextInst;
}
-
+
// If it's not a no-op copy, it clobbers the value in the destreg.
Spills.ClobberPhysReg(VirtReg);
ReusedOperands.markClobbered(VirtReg);