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[ReachingDefAnalysis] Fix management of MBBFrameObjsReachingDefs #124943

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Merged
michaelmaitland 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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28 changes: 16 additions & 12 deletions llvm/lib/CodeGen/ReachingDefAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -147,16 +147,9 @@ void ReachingDefAnalysis::processDefs(MachineInstr *MI) {
assert(FrameIndex >= 0 && "Can't handle negative frame indicies yet!");
if (!isFIDef(*MI, FrameIndex, TII))
continue;
if (MBBFrameObjsReachingDefs.contains(MBBNumber)) {
auto Frame2InstrIdx = MBBFrameObjsReachingDefs[MBBNumber];
if (Frame2InstrIdx.count(FrameIndex - ObjectIndexBegin) > 0)
Frame2InstrIdx[FrameIndex - ObjectIndexBegin].push_back(CurInstr);
else
Frame2InstrIdx[FrameIndex - ObjectIndexBegin] = {CurInstr};
} else {
MBBFrameObjsReachingDefs[MBBNumber] = {
{FrameIndex - ObjectIndexBegin, {CurInstr}}};
}

int Key = FrameIndex - ObjectIndexBegin;
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@topperc topperc Jan 31, 2025

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Why do we need to normalize the FrameIndex. Can't we use it as the key directly?

MBBFrameObjsReachingDefs[MBBNumber][Key].push_back(CurInstr);
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@topperc topperc Jan 31, 2025

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A map of maps is a kind of silly data structure. You can make the key a std::pair and use a single level map. Unless we need to be able to easily access the inner map for a single basic block.

}
if (!isValidRegDef(MO))
continue;
Expand Down Expand Up @@ -348,8 +341,19 @@ int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, Register Reg) const {

if (Reg.isStack()) {
int FrameIndex = Reg.stackSlotIndex();
for (int Def : MBBFrameObjsReachingDefs.lookup(MBBNumber).lookup(
FrameIndex - ObjectIndexBegin)) {
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())
return LatestDef;
auto &Defs = Lookup2->second;

for (int Def : Defs) {
if (Def >= InstId)
break;
DefRes = Def;
Expand Down
37 changes: 37 additions & 0 deletions llvm/test/CodeGen/RISCV/rda-stack.mir
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Expand Up @@ -149,3 +149,40 @@ body: |
$x10 = LD %stack.0, 0 :: (load (s64))
PseudoRET implicit $x10
...
---
name: test4
tracksRegLiveness: true
stack:
- { id: 0, name: '', type: default, offset: 0, size: 4, alignment: 4,
stack-id: default, callee-saved-register: '', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
- { id: 1, name: '', type: default, offset: 0, size: 4, alignment: 4,
stack-id: default, callee-saved-register: '', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
body: |
; CHECK: RDA results for test4
; CHECK-NEXT: $x10:{ }
; CHECK-NEXT: %stack.0:{ }
; CHECK-NEXT: 0: SD $x10, %stack.0, 0 :: (store (s64))
; CHECK-EMPTY:
; CHECK-NEXT: $x11:{ }
; CHECK-NEXT: %stack.0:{ 0 }
; CHECK-NEXT: 1: SD $x11, %stack.0, 0 :: (store (s64))
; CHECK-EMPTY:
; CHECK-NEXT: $x10:{ }
; CHECK-NEXT: %stack.1:{ }
; CHECK-NEXT: 2: SD $x10, %stack.1, 0 :: (store (s64))
; CHECK-EMPTY:
; CHECK-NEXT: $x11:{ }
; CHECK-NEXT: %stack.1:{ 2 }
; CHECK-NEXT: 3: SD $x11, %stack.1, 0 :: (store (s64))
; CHECK-EMPTY:
; CHECK-NEXT: 4: PseudoRET
bb.0.entry:
liveins: $x10, $x11
SD $x10, %stack.0, 0 :: (store (s64))
SD $x11, %stack.0, 0 :: (store (s64))
SD $x10, %stack.1, 0 :: (store (s64))
SD $x11, %stack.1, 0 :: (store (s64))
PseudoRET
...