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

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index bbf1e24873..be0b016b66 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -2029,8 +2029,12 @@ private:
         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 @@ private:
             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);