RegisterCoalescer: Forcibly leave SSA to avoid MIR test errors
Not sure how to produce a test that demonstrates the problem
today. The coalescer would have to introduce a verifier caught SSA
violation, like multiple defs of a virtual register. I'm not sure what
would do that now, but an upcoming patch will.
https://reviews.llvm.org/D156271
GitOrigin-RevId: 32a23aecf8002e181eb1022b8733ef8666b3241f
diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 2384621..516095a 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -4131,6 +4131,14 @@
else
JoinGlobalCopies = (EnableGlobalCopies == cl::BOU_TRUE);
+ // FIXME: MachineFunctionProperties cannot express the required pre-property
+ // no-SSA. When running a MIR testcase without any virtual register defs, the
+ // MIR parser assumes SSA. MachineFunctionPass::getClearedProperties is called
+ // after the pass is run, so the properties at this point say it's an SSA
+ // function. Forcibly clear it here so -verify-coalescing doesn't complain
+ // after multiple virtual register defs are introduced.
+ MRI->leaveSSA();
+
// If there are PHIs tracked by debug-info, they will need updating during
// coalescing. Build an index of those PHIs to ease updating.
SlotIndexes *Slots = LIS->getSlotIndexes();
