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[DA] disambiguate evolution of base addresses #116628

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Jan 30, 2025
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[DA] disambiguate evolution of base addresses #116628

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6 changes: 4 additions & 2 deletions llvm/lib/Analysis/DependenceAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -723,7 +723,10 @@ static AliasResult underlyingObjectsAlias(AAResults *AA,
MemoryLocation::getBeforeOrAfter(LocA.Ptr, LocA.AATags);
MemoryLocation LocBS =
MemoryLocation::getBeforeOrAfter(LocB.Ptr, LocB.AATags);
if (AA->isNoAlias(LocAS, LocBS))
BatchAAResults BAA(*AA);
BAA.enableCrossIterationMode();

if (BAA.isNoAlias(LocAS, LocBS))
return AliasResult::NoAlias;

// Check the underlying objects are the same
Expand All @@ -744,7 +747,6 @@ static AliasResult underlyingObjectsAlias(AAResults *AA,
return AliasResult::NoAlias;
}


// Returns true if the load or store can be analyzed. Atomic and volatile
// operations have properties which this analysis does not understand.
static
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159 changes: 159 additions & 0 deletions llvm/test/Analysis/DependenceAnalysis/FlipFlopBaseAddress.ll
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@@ -0,0 +1,159 @@
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -disable-output "-passes=print<da>" -aa-pipeline=basic-aa 2>&1 \
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Can use the update_analyze_checks support you added recently?

; RUN: | FileCheck %s

; Check that dependence analysis correctly handles flip-flop of base addresses.
; Bug 41488 - https://github.com/llvm/llvm-project/issues/41488

define float @bug41488_test1(float %f) {
; CHECK-LABEL: 'bug41488_test1'
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: %0 = load float, ptr %p, align 4
; CHECK-NEXT: da analyze - input [*]!
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: store float %f, ptr %q, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store float %f, ptr %q, align 4 --> Dst: store float %f, ptr %q, align 4
; CHECK-NEXT: da analyze - output [*]!
;
entry:
%g = alloca float, align 4
%h = alloca float, align 4
br label %for.body

for.body:
%p = phi float* [ %g, %entry ], [ %q, %for.body ]
%q = phi float* [ %h, %entry ], [ %p, %for.body ]
%0 = load float, float* %p, align 4
store float %f, float* %q, align 4
%branch_cond = fcmp ugt float %0, 0.0
br i1 %branch_cond, label %for.cond.cleanup, label %for.body

for.cond.cleanup:
ret float %f
}

define void @bug41488_test2(i32 %n) {
; CHECK-LABEL: 'bug41488_test2'
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: %0 = load float, ptr %p, align 4
; CHECK-NEXT: da analyze - input [*]!
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: store float 0.000000e+00, ptr %q, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store float 0.000000e+00, ptr %q, align 4 --> Dst: store float 0.000000e+00, ptr %q, align 4
; CHECK-NEXT: da analyze - output [*]!
;
entry:
%g = alloca float, align 4
%h = alloca float, align 4
br label %for.body

for.body:
%i = phi i32 [0, %entry ], [ %inc, %for.body ]
%p = phi float* [ %g, %entry ], [ %q, %for.body ]
%q = phi float* [ %h, %entry ], [ %p, %for.body ]
%0 = load float, float* %p, align 4
store float 0.0, float* %q, align 4
%inc = add nuw i32 %i, 1
%branch_cond = icmp ult i32 %i, %n
br i1 %branch_cond, label %for.body, label %for.cond.cleanup

for.cond.cleanup:
ret void
}

; Bug 53942 - https://github.com/llvm/llvm-project/issues/53942

define void @bug53942_foo(i32 noundef %n, ptr noalias nocapture noundef writeonly %A, ptr noalias nocapture noundef %B) {
; CHECK-LABEL: 'bug53942_foo'
; CHECK-NEXT: Src: %.pre = load double, ptr %B, align 8 --> Dst: %.pre = load double, ptr %B, align 8
; CHECK-NEXT: da analyze - consistent input [S]!
; CHECK-NEXT: Src: %.pre = load double, ptr %B, align 8 --> Dst: store double %.pre, ptr %arrayidx2, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store double %.pre, ptr %arrayidx2, align 8 --> Dst: store double %.pre, ptr %arrayidx2, align 8
; CHECK-NEXT: da analyze - output [*]!
;
entry:
%cmp8 = icmp sgt i32 %n, 1
br i1 %cmp8, label %for.body.preheader, label %for.cond.cleanup

for.body.preheader: ; preds = %entry
%wide.trip.count = zext nneg i32 %n to i64
br label %for.body

for.cond.cleanup: ; preds = %for.body, %entry
ret void

for.body: ; preds = %for.body.preheader, %for.body
%indvars.iv = phi i64 [ 1, %for.body.preheader ], [ %indvars.iv.next, %for.body ]
%ptr1.011 = phi ptr [ %A, %for.body.preheader ], [ %ptr2.09, %for.body ]
%ptr2.09 = phi ptr [ %B, %for.body.preheader ], [ %ptr1.011, %for.body ]
%.pre = load double, ptr %B, align 8
%arrayidx2 = getelementptr inbounds double, ptr %ptr1.011, i64 %indvars.iv
store double %.pre, ptr %arrayidx2, align 8
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond.not = icmp eq i64 %indvars.iv.next, %wide.trip.count
br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
}


; Bug 53942 - https://github.com/llvm/llvm-project/issues/53942

define void @bug53942_bar(i32 noundef %n, ptr noalias noundef %A, ptr noalias noundef %B) {
; CHECK-LABEL: 'bug53942_bar'
; CHECK-NEXT: Src: %0 = load double, ptr %arrayidx, align 8 --> Dst: %0 = load double, ptr %arrayidx, align 8
; CHECK-NEXT: da analyze - input [*]!
; CHECK-NEXT: Src: %0 = load double, ptr %arrayidx, align 8 --> Dst: store double %0, ptr %arrayidx8, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store double %0, ptr %arrayidx8, align 8 --> Dst: store double %0, ptr %arrayidx8, align 8
; CHECK-NEXT: da analyze - output [*]!
;
entry:
br label %for.cond

for.cond: ; preds = %for.inc, %entry
%i.0 = phi i32 [ 1, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, %n
br i1 %cmp, label %for.body, label %for.cond.cleanup

for.cond.cleanup: ; preds = %for.cond
br label %for.end

for.body: ; preds = %for.cond
%and = and i32 %i.0, 2
%tobool.not = icmp eq i32 %and, 0
br i1 %tobool.not, label %cond.false, label %cond.true

cond.true: ; preds = %for.body
br label %cond.end

cond.false: ; preds = %for.body
br label %cond.end

cond.end: ; preds = %cond.false, %cond.true
%cond = phi ptr [ %A, %cond.true ], [ %B, %cond.false ]
%and1 = and i32 %i.0, 2
%tobool2.not = icmp eq i32 %and1, 0
br i1 %tobool2.not, label %cond.false4, label %cond.true3

cond.true3: ; preds = %cond.end
br label %cond.end5

cond.false4: ; preds = %cond.end
br label %cond.end5

cond.end5: ; preds = %cond.false4, %cond.true3
%cond6 = phi ptr [ %B, %cond.true3 ], [ %A, %cond.false4 ]
%sub = add nsw i32 %i.0, -1
%idxprom = sext i32 %sub to i64
%arrayidx = getelementptr inbounds double, ptr %cond6, i64 %idxprom
%0 = load double, ptr %arrayidx, align 8
%idxprom7 = zext nneg i32 %i.0 to i64
%arrayidx8 = getelementptr inbounds double, ptr %cond, i64 %idxprom7
store double %0, ptr %arrayidx8, align 8
br label %for.inc

for.inc: ; preds = %cond.end5
%inc = add nuw nsw i32 %i.0, 1
br label %for.cond

for.end: ; preds = %for.cond.cleanup
ret void
}