diff options
Diffstat (limited to 'lib/CodeGen/VirtRegRewriter.cpp')
| -rw-r--r-- | lib/CodeGen/VirtRegRewriter.cpp | 8 |
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); |