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[Loads] Also consider getPointerAlignment when checking assumptions. (#…
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…120916)

Also use getPointerAlignment when trying to use alignment and
dereferenceable assumptions. This catches cases where dereferencable is
known via the assumption but alignment is known via getPointerAlignment
(e.g. via argument attribute or align of 1)

PR: #120916
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@fhahn
fhahn authored Jan 9, 2025
1 parent a6b7181 commit b6cda33
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Showing 2 changed files with 12 additions and 44 deletions.
6 changes: 4 additions & 2 deletions llvm/lib/Analysis/Loads.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -170,9 +170,10 @@ static bool isDereferenceableAndAlignedPointer(

if (CtxI) {
/// Look through assumes to see if both dereferencability and alignment can
/// be provent by an assume
/// be proven by an assume if needed.
RetainedKnowledge AlignRK;
RetainedKnowledge DerefRK;
bool IsAligned = V->getPointerAlignment(DL) >= Alignment;
if (getKnowledgeForValue(
V, {Attribute::Dereferenceable, Attribute::Alignment}, AC,
[&](RetainedKnowledge RK, Instruction *Assume, auto) {
Expand All @@ -182,7 +183,8 @@ static bool isDereferenceableAndAlignedPointer(
AlignRK = std::max(AlignRK, RK);
if (RK.AttrKind == Attribute::Dereferenceable)
DerefRK = std::max(DerefRK, RK);
if (AlignRK && DerefRK && AlignRK.ArgValue >= Alignment.value() &&
IsAligned |= AlignRK && AlignRK.ArgValue >= Alignment.value();
if (IsAligned && DerefRK &&
DerefRK.ArgValue >= Size.getZExtValue())
return true; // We have found what we needed so we stop looking
return false; // Other assumes may have better information. so
Expand Down
50 changes: 8 additions & 42 deletions llvm/test/Transforms/LoopVectorize/dereferenceable-info-from-assumption-constant-size.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -104,8 +104,8 @@ exit:
ret void
}

define void @deref_assumption_in_header_constant_trip_count_loop_invariant_ptr(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; CHECK-LABEL: define void @deref_assumption_in_header_constant_trip_count_loop_invariant_ptr(
define void @align_deref_assumption_in_header_constant_trip_count_loop_invariant_ptr(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; CHECK-LABEL: define void @align_deref_assumption_in_header_constant_trip_count_loop_invariant_ptr(
; CHECK-SAME: ptr noalias [[A:%.*]], ptr noalias [[B:%.*]], ptr noalias [[C:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(ptr [[A]], i64 4), "dereferenceable"(ptr [[A]], i64 4) ]
Expand Down Expand Up @@ -899,32 +899,15 @@ define void @deref_assumption_in_preheader_constant_trip_count_align_1(ptr noali
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[PRED_LOAD_CONTINUE2:.*]] ]
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[INDEX]], 0
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i32, ptr [[B]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i32, ptr [[TMP1]], i32 0
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <2 x i32>, ptr [[TMP2]], align 4
; CHECK-NEXT: [[TMP3:%.*]] = icmp sge <2 x i32> [[WIDE_LOAD]], zeroinitializer
; CHECK-NEXT: [[TMP4:%.*]] = xor <2 x i1> [[TMP3]], splat (i1 true)
; CHECK-NEXT: [[TMP5:%.*]] = extractelement <2 x i1> [[TMP4]], i32 0
; CHECK-NEXT: br i1 [[TMP5]], label %[[PRED_LOAD_IF:.*]], label %[[PRED_LOAD_CONTINUE:.*]]
; CHECK: [[PRED_LOAD_IF]]:
; CHECK-NEXT: [[TMP6:%.*]] = getelementptr i32, ptr [[A]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP7:%.*]] = load i32, ptr [[TMP6]], align 1
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <2 x i32> poison, i32 [[TMP7]], i32 0
; CHECK-NEXT: br label %[[PRED_LOAD_CONTINUE]]
; CHECK: [[PRED_LOAD_CONTINUE]]:
; CHECK-NEXT: [[TMP9:%.*]] = phi <2 x i32> [ poison, %[[VECTOR_BODY]] ], [ [[TMP8]], %[[PRED_LOAD_IF]] ]
; CHECK-NEXT: [[TMP10:%.*]] = extractelement <2 x i1> [[TMP4]], i32 1
; CHECK-NEXT: br i1 [[TMP10]], label %[[PRED_LOAD_IF1:.*]], label %[[PRED_LOAD_CONTINUE2]]
; CHECK: [[PRED_LOAD_IF1]]:
; CHECK-NEXT: [[TMP11:%.*]] = add i64 [[INDEX]], 1
; CHECK-NEXT: [[TMP12:%.*]] = getelementptr i32, ptr [[A]], i64 [[TMP11]]
; CHECK-NEXT: [[TMP13:%.*]] = load i32, ptr [[TMP12]], align 1
; CHECK-NEXT: [[TMP14:%.*]] = insertelement <2 x i32> [[TMP9]], i32 [[TMP13]], i32 1
; CHECK-NEXT: br label %[[PRED_LOAD_CONTINUE2]]
; CHECK: [[PRED_LOAD_CONTINUE2]]:
; CHECK-NEXT: [[TMP15:%.*]] = phi <2 x i32> [ [[TMP9]], %[[PRED_LOAD_CONTINUE]] ], [ [[TMP14]], %[[PRED_LOAD_IF1]] ]
; CHECK-NEXT: [[TMP5:%.*]] = getelementptr i32, ptr [[TMP6]], i32 0
; CHECK-NEXT: [[TMP15:%.*]] = load <2 x i32>, ptr [[TMP5]], align 1
; CHECK-NEXT: [[PREDPHI:%.*]] = select <2 x i1> [[TMP3]], <2 x i32> [[WIDE_LOAD]], <2 x i32> [[TMP15]]
; CHECK-NEXT: [[TMP16:%.*]] = getelementptr inbounds i32, ptr [[C]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP17:%.*]] = getelementptr inbounds i32, ptr [[TMP16]], i32 0
Expand Down Expand Up @@ -1168,32 +1151,15 @@ define void @deref_assumption_in_preheader_constant_trip_count_align_4_known_via
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[PRED_LOAD_CONTINUE2:.*]] ]
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[INDEX]], 0
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i32, ptr [[B]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i32, ptr [[TMP1]], i32 0
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <2 x i32>, ptr [[TMP2]], align 4
; CHECK-NEXT: [[TMP3:%.*]] = icmp sge <2 x i32> [[WIDE_LOAD]], zeroinitializer
; CHECK-NEXT: [[TMP4:%.*]] = xor <2 x i1> [[TMP3]], splat (i1 true)
; CHECK-NEXT: [[TMP5:%.*]] = extractelement <2 x i1> [[TMP4]], i32 0
; CHECK-NEXT: br i1 [[TMP5]], label %[[PRED_LOAD_IF:.*]], label %[[PRED_LOAD_CONTINUE:.*]]
; CHECK: [[PRED_LOAD_IF]]:
; CHECK-NEXT: [[TMP6:%.*]] = getelementptr i32, ptr [[A]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP7:%.*]] = load i32, ptr [[TMP6]], align 4
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <2 x i32> poison, i32 [[TMP7]], i32 0
; CHECK-NEXT: br label %[[PRED_LOAD_CONTINUE]]
; CHECK: [[PRED_LOAD_CONTINUE]]:
; CHECK-NEXT: [[TMP9:%.*]] = phi <2 x i32> [ poison, %[[VECTOR_BODY]] ], [ [[TMP8]], %[[PRED_LOAD_IF]] ]
; CHECK-NEXT: [[TMP10:%.*]] = extractelement <2 x i1> [[TMP4]], i32 1
; CHECK-NEXT: br i1 [[TMP10]], label %[[PRED_LOAD_IF1:.*]], label %[[PRED_LOAD_CONTINUE2]]
; CHECK: [[PRED_LOAD_IF1]]:
; CHECK-NEXT: [[TMP11:%.*]] = add i64 [[INDEX]], 1
; CHECK-NEXT: [[TMP12:%.*]] = getelementptr i32, ptr [[A]], i64 [[TMP11]]
; CHECK-NEXT: [[TMP13:%.*]] = load i32, ptr [[TMP12]], align 4
; CHECK-NEXT: [[TMP14:%.*]] = insertelement <2 x i32> [[TMP9]], i32 [[TMP13]], i32 1
; CHECK-NEXT: br label %[[PRED_LOAD_CONTINUE2]]
; CHECK: [[PRED_LOAD_CONTINUE2]]:
; CHECK-NEXT: [[TMP15:%.*]] = phi <2 x i32> [ [[TMP9]], %[[PRED_LOAD_CONTINUE]] ], [ [[TMP14]], %[[PRED_LOAD_IF1]] ]
; CHECK-NEXT: [[TMP5:%.*]] = getelementptr i32, ptr [[TMP6]], i32 0
; CHECK-NEXT: [[TMP15:%.*]] = load <2 x i32>, ptr [[TMP5]], align 4
; CHECK-NEXT: [[PREDPHI:%.*]] = select <2 x i1> [[TMP3]], <2 x i32> [[WIDE_LOAD]], <2 x i32> [[TMP15]]
; CHECK-NEXT: [[TMP16:%.*]] = getelementptr inbounds i32, ptr [[C]], i64 [[TMP0]]
; CHECK-NEXT: [[TMP17:%.*]] = getelementptr inbounds i32, ptr [[TMP16]], i32 0
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