[RS4GC] Remat in presence of phi and use live value
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llvm-svn: 282150
diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index 8291814..acefcd6 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -1976,7 +1976,8 @@
// Utility function which clones all instructions from "ChainToBase"
// and inserts them before "InsertBefore". Returns rematerialized value
// which should be used after statepoint.
- auto rematerializeChain = [&ChainToBase](Instruction *InsertBefore) {
+ auto rematerializeChain = [&ChainToBase](
+ Instruction *InsertBefore, Value *RootOfChain, Value *AlternateLiveBase) {
Instruction *LastClonedValue = nullptr;
Instruction *LastValue = nullptr;
for (Instruction *Instr: ChainToBase) {
@@ -1996,13 +1997,24 @@
assert(LastValue);
ClonedValue->replaceUsesOfWith(LastValue, LastClonedValue);
#ifndef NDEBUG
- // Assert that cloned instruction does not use any instructions from
- // this chain other than LastClonedValue
for (auto OpValue : ClonedValue->operand_values()) {
+ // Assert that cloned instruction does not use any instructions from
+ // this chain other than LastClonedValue
assert(!is_contained(ChainToBase, OpValue) &&
"incorrect use in rematerialization chain");
+ // Assert that the cloned instruction does not use the RootOfChain
+ // or the AlternateLiveBase.
+ assert(OpValue != RootOfChain && OpValue != AlternateLiveBase);
}
#endif
+ } else {
+ // For the first instruction, replace the use of unrelocated base i.e.
+ // RootOfChain/OrigRootPhi, with the corresponding PHI present in the
+ // live set. They have been proved to be the same PHI nodes. Note
+ // that the *only* use of the RootOfChain in the ChainToBase list is
+ // the first Value in the list.
+ if (RootOfChain != AlternateLiveBase)
+ ClonedValue->replaceUsesOfWith(RootOfChain, AlternateLiveBase);
}
LastClonedValue = ClonedValue;
@@ -2017,7 +2029,8 @@
if (CS.isCall()) {
Instruction *InsertBefore = CS.getInstruction()->getNextNode();
assert(InsertBefore);
- Instruction *RematerializedValue = rematerializeChain(InsertBefore);
+ Instruction *RematerializedValue = rematerializeChain(
+ InsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
Info.RematerializedValues[RematerializedValue] = LiveValue;
} else {
InvokeInst *Invoke = cast<InvokeInst>(CS.getInstruction());
@@ -2027,10 +2040,10 @@
Instruction *UnwindInsertBefore =
&*Invoke->getUnwindDest()->getFirstInsertionPt();
- Instruction *NormalRematerializedValue =
- rematerializeChain(NormalInsertBefore);
- Instruction *UnwindRematerializedValue =
- rematerializeChain(UnwindInsertBefore);
+ Instruction *NormalRematerializedValue = rematerializeChain(
+ NormalInsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
+ Instruction *UnwindRematerializedValue = rematerializeChain(
+ UnwindInsertBefore, RootOfChain, Info.PointerToBase[LiveValue]);
Info.RematerializedValues[NormalRematerializedValue] = LiveValue;
Info.RematerializedValues[UnwindRematerializedValue] = LiveValue;