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[DSE] Update dereferenceable attributes when adjusting memintrinsic ptr #125073

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Merged
merged 4 commits into from
Feb 18, 2025
Merged

[DSE] Update dereferenceable attributes when adjusting memintrinsic ptr #125073

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6b014c5
[DSE] Update dereferenceable attributes when adjusting memintrinsic ptr
bjope Jan 30, 2025
f6f7025
fixup formatting
bjope Jan 30, 2025
8b8ce48
Simplify the solution by just dropping the dereferenceable attrs
bjope Jan 30, 2025
0b58bf4
Change the logic to drop all attributes that we do not explicitly
bjope Jan 31, 2025
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5 changes: 5 additions & 0 deletions llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -644,6 +644,11 @@ static bool tryToShorten(Instruction *DeadI, int64_t &DeadStart,
DeadI->getIterator());
NewDestGEP->setDebugLoc(DeadIntrinsic->getDebugLoc());
DeadIntrinsic->setDest(NewDestGEP);
// Simply drop any dereferenceable attributes (memset with a constant length
// already implies dereferenceability by itself, so dropping is simpler than
// trying to adjust the dereferenceable size).
DeadIntrinsic->removeParamAttr(0, Attribute::Dereferenceable);
DeadIntrinsic->removeParamAttr(0, Attribute::DereferenceableOrNull);
}

// Update attached dbg.assign intrinsics. Assume 8-bit byte.
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30 changes: 30 additions & 0 deletions llvm/test/Transforms/DeadStoreElimination/OverwriteStoreBegin.ll
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Expand Up @@ -402,3 +402,33 @@ entry:
store i64 1, ptr %p, align 1
ret void
}

; Verify that we adjust/drop the dereferenceable attribute.
define void @dereferenceable(ptr nocapture %p) {
; CHECK-LABEL: @dereferenceable(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds i8, ptr [[P:%.*]], i64 4
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4 [[TMP0]], i8 0, i64 24, i1 false)
; CHECK-NEXT: store i32 1, ptr [[P]], align 4
; CHECK-NEXT: ret void
;
entry:
call void @llvm.memset.p0.i64(ptr dereferenceable(28) align 4 %p, i8 0, i64 28, i1 false)
store i32 1, ptr %p, align 4
ret void
}

; Verify that we adjust/drop the dereferenceable_or_null attribute.
define void @dereferenceable_or_null(ptr nocapture %p) {
; CHECK-LABEL: @dereferenceable_or_null(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds i8, ptr [[P:%.*]], i64 8
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4 [[TMP0]], i8 0, i64 20, i1 false)
; CHECK-NEXT: store i64 1, ptr [[P]], align 4
; CHECK-NEXT: ret void
;
entry:
call void @llvm.memset.p0.i64(ptr dereferenceable_or_null(28) align 4 %p, i8 0, i64 28, i1 false)
store i64 1, ptr %p, align 4
ret void
}