[RegAlloc] Strengthen asserts in LiveRangeEdit::scanRemattable [nfc] #160765
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We should always be able to find the VNInfo in the original live interval which corresponds to the subset we're trying to spill, and the only cases where we have a VNInfo without a definition instruction are if the vni is unused, or corresponds to a phi. Adjust the code structure to explicitly check for PHIDef, and assert the stronger conditions.
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@llvm/pr-subscribers-llvm-regalloc Author: Philip Reames (preames) ChangesWe should always be able to find the VNInfo in the original live interval which corresponds to the subset we're trying to spill, and the only cases where we have a VNInfo without a definition instruction are if the vni is unused, or corresponds to a phi. Adjust the code structure to explicitly check for PHIDef, and assert the stronger conditions. Full diff: https://github.com/llvm/llvm-project/pull/160765.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index 2f65be51bb726..dc1121d7d9e28 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -75,11 +75,11 @@ void LiveRangeEdit::scanRemattable() {
Register Original = VRM->getOriginal(getReg());
LiveInterval &OrigLI = LIS.getInterval(Original);
VNInfo *OrigVNI = OrigLI.getVNInfoAt(VNI->def);
- if (!OrigVNI)
+ assert(OrigVNI && "Corrupt interval mapping?");
+ if (OrigVNI->isPHIDef())
continue;
MachineInstr *DefMI = LIS.getInstructionFromIndex(OrigVNI->def);
- if (!DefMI)
- continue;
+ assert(DefMI && "Missing instruction for def slot");
if (TII.isReMaterializable(*DefMI))
Remattable.insert(OrigVNI);
}
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Slightly skeptical review is appreciated. I want to make sure I'm not missing something in the invariants here. |
arsenm
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Sep 26, 2025
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…anRemattable [nfc]" (#160897) Reverts llvm/llvm-project#160765. Failures on buildbot indicate second assertion does not in fact hold.
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…lvm#160765) We should always be able to find the VNInfo in the original live interval which corresponds to the subset we're trying to spill, and the only cases where we have a VNInfo without a definition instruction are if the vni is unused, or corresponds to a phi. Adjust the code structure to explicitly check for PHIDef, and assert the stronger conditions.
mahesh-attarde
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Oct 3, 2025
…e [nfc]" (llvm#160897) Reverts llvm#160765. Failures on buildbot indicate second assertion does not in fact hold.
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We should always be able to find the VNInfo in the original live interval which corresponds to the subset we're trying to spill, and the only cases where we have a VNInfo without a definition instruction are if the vni is unused, or corresponds to a phi. Adjust the code structure to explicitly check for PHIDef, and assert the stronger conditions.