[LiveRangeCalc] Fix isJointlyDominated #116020
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Check that every path from the entry block to the use block passes through at least one def block. Previously we only checked that at least one path passed through a def block.
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@llvm/pr-subscribers-llvm-regalloc Author: Jay Foad (jayfoad) ChangesCheck that every path from the entry block to the use block passes Full diff: https://github.com/llvm/llvm-project/pull/116020.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/LiveRangeCalc.cpp b/llvm/lib/CodeGen/LiveRangeCalc.cpp
index dfd4d2910955af..1a9bc694ed0fdc 100644
--- a/llvm/lib/CodeGen/LiveRangeCalc.cpp
+++ b/llvm/lib/CodeGen/LiveRangeCalc.cpp
@@ -441,15 +441,21 @@ bool LiveRangeCalc::isJointlyDominated(const MachineBasicBlock *MBB,
for (SlotIndex I : Defs)
DefBlocks.set(Indexes.getMBBFromIndex(I)->getNumber());
+ unsigned EntryNum = MF.front().getNumber();
SetVector<unsigned> PredQueue;
PredQueue.insert(MBB->getNumber());
for (unsigned i = 0; i != PredQueue.size(); ++i) {
unsigned BN = PredQueue[i];
if (DefBlocks[BN])
- return true;
+ continue;
+ if (BN == EntryNum) {
+ // We found a path from MBB back to the entry block without hitting any of
+ // the def blocks.
+ return false;
+ }
const MachineBasicBlock *B = MF.getBlockNumbered(BN);
for (const MachineBasicBlock *P : B->predecessors())
PredQueue.insert(P->getNumber());
}
- return false;
+ return true;
}
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Contributor
Author
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I'll try to come up with a test case using MachineVerifier. |
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Author
Actually MachineVerifier only uses this function to verify LiveIntervals and I can't write a MIR test for malformed LiveIntervals, so I don't have any way to test this. |
kparzysz
approved these changes
Nov 13, 2024
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kparzysz
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kparzysz
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LGTM. Thanks for catching this!
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/10779 Here is the relevant piece of the build log for the reference |
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Check that every path from the entry block to the use block passes
through at least one def block. Previously we only checked that at least
one path passed through a def block.