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[NewGVN] Fix caching for OpIsSafeForPhiOfOps #98340

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Jul 12, 2024
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[NewGVN] Fix caching for OpIsSafeForPhiOfOps #98340

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23 changes: 16 additions & 7 deletions llvm/lib/Transforms/Scalar/NewGVN.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -529,7 +529,11 @@ class NewGVN {
// IR.
SmallPtrSet<const Instruction *, 8> PHINodeUses;

DenseMap<const Value *, bool> OpSafeForPHIOfOps;
// The cached results, in general, are only valid for the specific block where
// they were computed. The unsigned part of the key is a unique block
// identifier
DenseMap<std::pair<const Value *, unsigned>, bool> OpSafeForPHIOfOps;
unsigned CacheIdx;

// Map a temporary instruction we created to a parent block.
DenseMap<const Value *, BasicBlock *> TempToBlock;
Expand Down Expand Up @@ -2600,19 +2604,19 @@ bool NewGVN::OpIsSafeForPHIOfOps(Value *V, const BasicBlock *PHIBlock,
if (!isa<Instruction>(I))
continue;

auto OISIt = OpSafeForPHIOfOps.find(I);
auto OISIt = OpSafeForPHIOfOps.find({I, CacheIdx});
if (OISIt != OpSafeForPHIOfOps.end())
return OISIt->second;

// Keep walking until we either dominate the phi block, or hit a phi, or run
// out of things to check.
if (DT->properlyDominates(getBlockForValue(I), PHIBlock)) {
OpSafeForPHIOfOps.insert({I, true});
OpSafeForPHIOfOps.insert({{I, CacheIdx}, true});
continue;
}
// PHI in the same block.
if (isa<PHINode>(I) && getBlockForValue(I) == PHIBlock) {
OpSafeForPHIOfOps.insert({I, false});
OpSafeForPHIOfOps.insert({{I, CacheIdx}, false});
return false;
}

Expand All @@ -2631,10 +2635,10 @@ bool NewGVN::OpIsSafeForPHIOfOps(Value *V, const BasicBlock *PHIBlock,
if (!isa<Instruction>(Op))
continue;
// Stop now if we find an unsafe operand.
auto OISIt = OpSafeForPHIOfOps.find(OrigI);
auto OISIt = OpSafeForPHIOfOps.find({OrigI, CacheIdx});
if (OISIt != OpSafeForPHIOfOps.end()) {
if (!OISIt->second) {
OpSafeForPHIOfOps.insert({I, false});
OpSafeForPHIOfOps.insert({{I, CacheIdx}, false});
return false;
}
continue;
Expand All @@ -2644,7 +2648,7 @@ bool NewGVN::OpIsSafeForPHIOfOps(Value *V, const BasicBlock *PHIBlock,
Worklist.push_back(cast<Instruction>(Op));
}
}
OpSafeForPHIOfOps.insert({V, true});
OpSafeForPHIOfOps.insert({{V, CacheIdx}, true});
return true;
}

Expand Down Expand Up @@ -3297,6 +3301,7 @@ void NewGVN::verifyIterationSettled(Function &F) {
TouchedInstructions.set();
TouchedInstructions.reset(0);
OpSafeForPHIOfOps.clear();
CacheIdx = 0;
iterateTouchedInstructions();
DenseSet<std::pair<const CongruenceClass *, const CongruenceClass *>>
EqualClasses;
Expand Down Expand Up @@ -3400,6 +3405,8 @@ void NewGVN::iterateTouchedInstructions() {
<< " because it is unreachable\n");
continue;
}
// Use the appropriate cache for "OpIsSafeForPHIOfOps".
CacheIdx = RPOOrdering.lookup(DT->getNode(CurrBlock)) - 1;
updateProcessedCount(CurrBlock);
}
// Reset after processing (because we may mark ourselves as touched when
Expand Down Expand Up @@ -3479,6 +3486,8 @@ bool NewGVN::runGVN() {
LLVM_DEBUG(dbgs() << "Block " << getBlockName(&F.getEntryBlock())
<< " marked reachable\n");
ReachableBlocks.insert(&F.getEntryBlock());
// Use index corresponding to entry block.
CacheIdx = 0;

iterateTouchedInstructions();
verifyMemoryCongruency();
Expand Down
100 changes: 100 additions & 0 deletions llvm/test/Transforms/NewGVN/cache-safe-phiofops.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,100 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=newgvn < %s | FileCheck %s

define i32 @unsafe(i1 %arg, i32 %arg1) {
; CHECK-LABEL: define i32 @unsafe(
; CHECK-SAME: i1 [[ARG:%.*]], i32 [[ARG1:%.*]]) {
; CHECK-NEXT: [[BB:.*:]]
; CHECK-NEXT: br label %[[BB4:.*]]
; CHECK: [[BB4]]:
; CHECK-NEXT: br i1 [[ARG]], label %[[BB6:.*]], label %[[BB5:.*]]
; CHECK: [[BB5]]:
; CHECK-NEXT: br label %[[BB6]]
; CHECK: [[BB6]]:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ [[ARG1]], %[[BB5]] ], [ 0, %[[BB4]] ]
; CHECK-NEXT: [[SREM:%.*]] = srem i32 [[ARG1]], [[PHI]]
; CHECK-NEXT: store i32 [[SREM]], ptr null, align 4
; CHECK-NEXT: br i1 [[ARG]], label %[[BB8:.*]], label %[[BB7:.*]]
; CHECK: [[BB7]]:
; CHECK-NEXT: br i1 true, label %[[BB8]], label %[[BB5]]
; CHECK: [[BB8]]:
; CHECK-NEXT: [[PHIOFOPS:%.*]] = phi i32 [ [[ARG1]], %[[BB6]] ], [ 0, %[[BB7]] ]
; CHECK-NEXT: [[PHI9:%.*]] = phi i32 [ 0, %[[BB7]] ], [ 1, %[[BB6]] ]
; CHECK-NEXT: store i32 [[PHIOFOPS]], ptr null, align 4
; CHECK-NEXT: br label %[[BB4]]
;
bb:
br label %bb4

bb4: ; preds = %bb8, %bb
br i1 %arg, label %bb6, label %bb5

bb5: ; preds = %bb7, %bb4
br label %bb6

bb6: ; preds = %bb5, %bb4
%phi = phi i32 [ %arg1, %bb5 ], [ 0, %bb4 ]
%or = or i32 %phi, %arg1
%srem = srem i32 %or, %phi
store i32 %srem, ptr null, align 4
br i1 %arg, label %bb8, label %bb7

bb7: ; preds = %bb6
br i1 true, label %bb8, label %bb5

bb8: ; preds = %bb7, %bb6
%phi9 = phi i32 [ 0, %bb7 ], [ 1, %bb6 ]
%mul = mul i32 %phi9, %or
store i32 %mul, ptr null, align 4
br label %bb4
}

define i32 @unsafe_load(i1 %arg) {
; CHECK-LABEL: define i32 @unsafe_load(
; CHECK-SAME: i1 [[ARG:%.*]]) {
; CHECK-NEXT: [[BB:.*:]]
; CHECK-NEXT: br label %[[BB1:.*]]
; CHECK: [[BB1]]:
; CHECK-NEXT: br i1 [[ARG]], label %[[BB3:.*]], label %[[BB2:.*]]
; CHECK: [[BB2]]:
; CHECK-NEXT: br label %[[BB3]]
; CHECK: [[BB3]]:
; CHECK-NEXT: [[PHI4:%.*]] = phi i32 [ 1, %[[BB2]] ], [ 0, %[[BB1]] ]
; CHECK-NEXT: [[LOAD:%.*]] = load i32, ptr null, align 4
; CHECK-NEXT: [[SREM:%.*]] = srem i32 [[LOAD]], [[PHI4]]
; CHECK-NEXT: store i32 [[SREM]], ptr null, align 4
; CHECK-NEXT: br i1 [[ARG]], label %[[BB6:.*]], label %[[BB5:.*]]
; CHECK: [[BB5]]:
; CHECK-NEXT: br i1 true, label %[[BB6]], label %[[BB2]]
; CHECK: [[BB6]]:
; CHECK-NEXT: [[PHIOFOPS:%.*]] = phi i32 [ [[LOAD]], %[[BB3]] ], [ 0, %[[BB5]] ]
; CHECK-NEXT: [[PHI7:%.*]] = phi i32 [ 0, %[[BB5]] ], [ 1, %[[BB3]] ]
; CHECK-NEXT: store i32 [[PHIOFOPS]], ptr null, align 4
; CHECK-NEXT: br label %[[BB1]]
;
bb:
br label %bb1

bb1: ; preds = %bb6, %bb
br i1 %arg, label %bb3, label %bb2

bb2: ; preds = %bb5, %bb1
%phi = phi i32 [ 1, %bb1 ], [ 0, %bb5 ]
br label %bb3

bb3: ; preds = %bb2, %bb1
%phi4 = phi i32 [ %phi, %bb2 ], [ 0, %bb1 ]
%load = load i32, ptr null, align 4
%srem = srem i32 %load, %phi4
store i32 %srem, ptr null, align 4
br i1 %arg, label %bb6, label %bb5

bb5: ; preds = %bb3
br i1 true, label %bb6, label %bb2

bb6: ; preds = %bb5, %bb3
%phi7 = phi i32 [ 0, %bb5 ], [ 1, %bb3 ]
%mul = mul i32 %phi7, %load
store i32 %mul, ptr null, align 4
br label %bb1
}
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