[PATCH] D56151: [DebugInfo] PR40010: Avoid register coalesing altering DBG_VALUE valuations

[Vedant Kumar via Phabricator via llvm-commits]

vsk added a comment.

Thanks for working on this.

As you pointed out in llvm.org/PR40010, we do have a general problem of leaving around DBG_VALUE instructions which should be dead/undef but aren't. Do you think it would be possible/worthwhile to diagnose this issue in MachineVerifier?



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Comment at: lib/CodeGen/RegisterCoalescer.cpp:1895
+  SmallVector<MachineInstr *, 4> DbgValuesToChange;
+  for (MachineRegisterInfo::reg_instr_iterator
+           I = MRI->reg_instr_begin(CP.getSrcReg()),
----------------
Using MachineRegisterInfo::reg_instructions might aid readability here. Any reason not to?


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Comment at: lib/CodeGen/RegisterCoalescer.cpp:1901
+    if (UseMI->isDebugValue() && UseMI->getOperand(0).isReg() &&
+        TargetRegisterInfo::isVirtualRegister(CP.getDstReg()) &&
+        mergingChangesDbgValue(UseMI, LIS->getInterval(CP.getDstReg())))
----------------
Could you explain why it's sufficient to fix up coalescer pairs in which the destination is a vreg?


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