[MachineSinking] Conservatively clear kill flags after coalescing.
This solves the problem of having a kill flag inside a loop
with a definition of the register prior to the loop:
%vreg368<def> ...
Inside loop:
%vreg520<def> = COPY %vreg368
%vreg568<def,tied1> = add %vreg341<tied0>, %vreg520<kill>
=> was coalesced into =>
%vreg568<def,tied1> = add %vreg341<tied0>, %vreg368<kill>
MachineVerifier then complained:
*** Bad machine code: Virtual register killed in block, but needed live out. ***
The kill flag for %vreg368 is incorrect, and is cleared by this patch.
This is similar to the clearing done at the end of
MachineSinking::SinkInstruction().
Patch provided by Jonas Paulsson.
Reviewed by Quentin Colombet and Juergen Ributzka.
llvm-svn: 217427
diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 7782001..261af54 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -157,6 +157,11 @@
DEBUG(dbgs() << "*** to: " << *MI);
MRI->replaceRegWith(DstReg, SrcReg);
MI->eraseFromParent();
+
+ // Conservatively, clear any kill flags, since it's possible that they are no
+ // longer correct.
+ MRI->clearKillFlags(SrcReg);
+
++NumCoalesces;
return true;
}