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[LVI] Handle nonnull attributes at callsite #125377

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Merged
dtcxzyw merged 5 commits into from
Feb 3, 2025
Merged

[LVI] Handle nonnull attributes at callsite #125377

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bcc2746
[CVP] Add pre-commit tests. NFC.
dtcxzyw Feb 2, 2025
c3bacf0
[LVI] Handle nonnull at callsite
dtcxzyw Feb 2, 2025
498ac15
[LVI] Address review comments.
dtcxzyw Feb 2, 2025
074099d
[CVP] Add more tests. NFC.
dtcxzyw Feb 2, 2025
54cb334
[LVI] Fix miscompilation
dtcxzyw Feb 2, 2025
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13 changes: 11 additions & 2 deletions llvm/lib/Analysis/LazyValueInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -622,10 +622,12 @@ LazyValueInfoImpl::solveBlockValueImpl(Value *Val, BasicBlock *BB) {
return getFromRangeMetadata(BBI);
}

static void AddNonNullPointer(Value *Ptr, NonNullPointerSet &PtrSet) {
static void AddNonNullPointer(Value *Ptr, NonNullPointerSet &PtrSet,
bool IsDereferenced = true) {
// TODO: Use NullPointerIsDefined instead.
if (Ptr->getType()->getPointerAddressSpace() == 0)
PtrSet.insert(getUnderlyingObject(Ptr));
PtrSet.insert(IsDereferenced ? getUnderlyingObject(Ptr)
: Ptr->stripInBoundsOffsets());
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@nikic nikic Feb 2, 2025

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As a followup, it may be worth checking whether always using stripInBoundsOffset() has a positive effect on llvm-opt-benchmark. The lookup always uses stripInBoundsOffset(), so currently there is mismatch between getUnderlyingObject on one side an stripInBoundsOffset on the other and it may give better results to always use only stripInBoundsOffset.

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@dtcxzyw dtcxzyw Feb 3, 2025

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It is worse than getUnderlyingObject.

}

static void AddNonNullPointersByInstruction(
Expand All @@ -644,6 +646,13 @@ static void AddNonNullPointersByInstruction(
AddNonNullPointer(MI->getRawDest(), PtrSet);
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
AddNonNullPointer(MTI->getRawSource(), PtrSet);
} else if (auto *CB = dyn_cast<CallBase>(I)) {
for (auto &U : CB->args()) {
if (U->getType()->isPointerTy() &&
CB->paramHasNonNullAttr(CB->getArgOperandNo(&U),
/*AllowUndefOrPoison=*/false))
AddNonNullPointer(U.get(), PtrSet, /*IsDereferenced=*/false);
}
}
}

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101 changes: 101 additions & 0 deletions llvm/test/Transforms/CorrelatedValuePropagation/non-null.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -344,4 +344,105 @@ define i1 @test_store_same_block(ptr %arg) {
ret i1 %cmp
}


define i1 @test_known_nonnull_at_callsite(ptr %src) {
; CHECK-LABEL: @test_known_nonnull_at_callsite(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @callee(ptr noundef nonnull [[SRC:%.*]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 false
;
entry:
call void @callee(ptr noundef nonnull %src)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

define i1 @test_known_nonnull_mixed(ptr %src) {
; CHECK-LABEL: @test_known_nonnull_mixed(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @callee2(ptr nonnull [[SRC:%.*]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 false
;
entry:
call void @callee2(ptr nonnull %src)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

define i1 @test_known_nonnull_at_callsite_dereferenceable(ptr %src) {
; CHECK-LABEL: @test_known_nonnull_at_callsite_dereferenceable(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @callee(ptr dereferenceable(1) [[SRC:%.*]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 false
;
entry:
call void @callee(ptr dereferenceable(1) %src)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

define i1 @test_known_nonnull_at_callsite_gep_inbounds(ptr %src, i64 %x) {
; CHECK-LABEL: @test_known_nonnull_at_callsite_gep_inbounds(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr [[SRC:%.*]], i64 [[X:%.*]]
; CHECK-NEXT: call void @callee(ptr noundef nonnull [[GEP]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 false
;
entry:
%gep = getelementptr inbounds i8, ptr %src, i64 %x
call void @callee(ptr noundef nonnull %gep)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

; Negative tests

define i1 @test_known_nonnull_at_callsite_without_noundef(ptr %src) {
; CHECK-LABEL: @test_known_nonnull_at_callsite_without_noundef(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @callee(ptr nonnull [[SRC:%.*]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 [[NONNULL]]
;
entry:
call void @callee(ptr nonnull %src)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

define i1 @test_known_nonnull_at_callsite_dereferenceable_null_is_defined(ptr %src) #0 {
; CHECK-LABEL: @test_known_nonnull_at_callsite_dereferenceable_null_is_defined(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @callee(ptr dereferenceable(1) [[SRC:%.*]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 [[NONNULL]]
;
entry:
call void @callee(ptr dereferenceable(1) %src)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

define i1 @test_known_nonnull_at_callsite_gep_without_inbounds(ptr %src, i64 %x) {
; CHECK-LABEL: @test_known_nonnull_at_callsite_gep_without_inbounds(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[SRC:%.*]], i64 [[X:%.*]]
; CHECK-NEXT: call void @callee(ptr noundef nonnull [[GEP]])
; CHECK-NEXT: [[NONNULL:%.*]] = icmp eq ptr [[SRC]], null
; CHECK-NEXT: ret i1 [[NONNULL]]
;
entry:
%gep = getelementptr i8, ptr %src, i64 %x
call void @callee(ptr noundef nonnull %gep)
%nonnull = icmp eq ptr %src, null
ret i1 %nonnull
}

declare void @callee(ptr)
declare void @callee2(ptr noundef)

attributes #0 = { null_pointer_is_valid }