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[ReachingDefAnalysis] Fix management of MBBFrameObjsReachingDefs #124943

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Merged
merged 5 commits into from
Feb 4, 2025
Merged

[ReachingDefAnalysis] Fix management of MBBFrameObjsReachingDefs #124943

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f14a174
precommit test case
michaelmaitland Jan 30, 2025
af0058b
[ReachingDefAnalysis][NFC] Fix management of MBBFrameObjsReachingDefs
michaelmaitland Jan 29, 2025
eab7c39
fixup! use FrameIndex as key; simplify map
michaelmaitland Jan 31, 2025
7dca773
fixup! use correct key
michaelmaitland Jan 31, 2025
bf1fe4f
fixup! add fixedStack
michaelmaitland Feb 4, 2025
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10 changes: 5 additions & 5 deletions llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
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Original file line number Diff line number Diff line change
Expand Up @@ -141,12 +141,12 @@ class ReachingDefAnalysis : public MachineFunctionPass {
DenseMap<MachineInstr *, int> InstIds;

MBBReachingDefsInfo MBBReachingDefs;

/// MBBFrameObjsReachingDefs[{i, j}] is a list of instruction indices
/// (relative to begining of MBB i) that define frame index j in MBB i. This
/// is used in answering reaching definition queries.
using MBBFrameObjsReachingDefsInfo =
DenseMap<unsigned, DenseMap<int, SmallVector<int>>>;
// MBBFrameObjsReachingDefs[i][j] is a list of instruction indices (relative
// to begining of MBB) that define frame index (j +
// MF->getFrameInfo().getObjectIndexBegin()) in MBB i. This is used in
// answering reaching definition queries.
DenseMap<std::pair<unsigned, int>, SmallVector<int>>;
MBBFrameObjsReachingDefsInfo MBBFrameObjsReachingDefs;

/// Default values are 'nothing happened a long time ago'.
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15 changes: 4 additions & 11 deletions llvm/lib/CodeGen/ReachingDefAnalysis.cpp
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Expand Up @@ -147,9 +147,7 @@ void ReachingDefAnalysis::processDefs(MachineInstr *MI) {
assert(FrameIndex >= 0 && "Can't handle negative frame indicies yet!");
if (!isFIDef(*MI, FrameIndex, TII))
continue;

int Key = FrameIndex - ObjectIndexBegin;
MBBFrameObjsReachingDefs[MBBNumber][Key].push_back(CurInstr);
MBBFrameObjsReachingDefs[{MBBNumber, FrameIndex}].push_back(CurInstr);
}
if (!isValidRegDef(MO))
continue;
Expand Down Expand Up @@ -344,15 +342,10 @@ int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, Register Reg) const {
int Key = FrameIndex - ObjectIndexBegin;

// Check that there was a reaching def.
auto Lookup1 = MBBFrameObjsReachingDefs.find(MBBNumber);
if (Lookup1 == MBBFrameObjsReachingDefs.end())
return LatestDef;
auto &InnerMap = Lookup1->second;
auto Lookup2 = InnerMap.find(Key);
if (Lookup2 == InnerMap.end())
auto Lookup = MBBFrameObjsReachingDefs.find({MBBNumber, Key});
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@topperc topperc Jan 31, 2025

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Doesn't this need to use FrameIndex instead of Key?

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@michaelmaitland michaelmaitland Jan 31, 2025

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yes, forgot to update. thanks

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@topperc topperc Jan 31, 2025 •
edited
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So there's no testing? Or is it because object begin was 0?

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@michaelmaitland michaelmaitland Jan 31, 2025

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There is no testing for a non-zero ObjectIndexBegin, so it ended up behaving as if Key == FrameIndex. Do you want me to add a test for a non-zero ObjectIndexBegin?

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@michaelmaitland michaelmaitland Feb 4, 2025

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@topperc test added. It doesn't matter anymore though since we no longer care about ObjectIndexBegin.

if (Lookup == MBBFrameObjsReachingDefs.end())
return LatestDef;
auto &Defs = Lookup2->second;

auto &Defs = Lookup->second;
for (int Def : Defs) {
if (Def >= InstId)
break;
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