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[DA] Add test where WeakCrossingSIV misses dependency due to overflow (NFC) #158281

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[DA] Add test where WeakCrossingSIV misses dependency due to overflow (NFC) #158281

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38b8bdd
[DA] Add overflow check in ExactSIV
kasuga-fj Sep 5, 2025
a4f0f1f
fix comment
kasuga-fj Sep 16, 2025
146b38e
Revert "fix comment"
kasuga-fj Sep 19, 2025
bdde305
[DA] Add test where WeakCrossingSIV misses dependency due to overflow
kasuga-fj Sep 12, 2025
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14 changes: 13 additions & 1 deletion llvm/lib/Analysis/DependenceAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1170,6 +1170,15 @@ const SCEVConstant *DependenceInfo::collectConstantUpperBound(const Loop *L,
return nullptr;
}

/// Returns \p A - \p B if it guaranteed not to signed wrap. Otherwise returns
/// nullptr. \p A and \p B must have the same integer type.
static const SCEV *minusSCEVNoSignedOverflow(const SCEV *A, const SCEV *B,
ScalarEvolution &SE) {
if (SE.willNotOverflow(Instruction::Sub, /*Signed=*/true, A, B))
return SE.getMinusSCEV(A, B);
return nullptr;
}

// testZIV -
// When we have a pair of subscripts of the form [c1] and [c2],
// where c1 and c2 are both loop invariant, we attack it using
Expand Down Expand Up @@ -1626,7 +1635,9 @@ bool DependenceInfo::exactSIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
assert(0 < Level && Level <= CommonLevels && "Level out of range");
Level--;
Result.Consistent = false;
const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
const SCEV *Delta = minusSCEVNoSignedOverflow(DstConst, SrcConst, *SE);
if (!Delta)
return false;
LLVM_DEBUG(dbgs() << "\t Delta = " << *Delta << "\n");
NewConstraint.setLine(SrcCoeff, SE->getNegativeSCEV(DstCoeff), Delta,
CurLoop);
Expand Down Expand Up @@ -1716,6 +1727,7 @@ bool DependenceInfo::exactSIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
// explore directions
unsigned NewDirection = Dependence::DVEntry::NONE;
APInt LowerDistance, UpperDistance;
// TODO: Overflow check may be needed.
if (TA.sgt(TB)) {
LowerDistance = (TY - TX) + (TA - TB) * TL;
UpperDistance = (TY - TX) + (TA - TB) * TU;
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Analysis/DependenceAnalysis/ExactSIV.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -841,7 +841,7 @@ define void @exact14(ptr %A) {
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: da analyze - output [*|<]!
; CHECK-SIV-ONLY-NEXT: Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
Expand Down
224 changes: 224 additions & 0 deletions llvm/test/Analysis/DependenceAnalysis/WeakCrossingSIV.ll
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@@ -1,6 +1,8 @@
; 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 \
; RUN: | FileCheck %s
; RUN: opt < %s -disable-output "-passes=print<da>" -da-run-siv-routines-only 2>&1 \
; RUN: | FileCheck %s --check-prefix=CHECK-SIV-ONLY

; ModuleID = 'WeakCrossingSIV.bc'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
Expand All @@ -26,6 +28,20 @@ define void @weakcrossing0(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing0'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - flow [0|<]!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
%cmp1 = icmp eq i64 %n, 0
br i1 %cmp1, label %for.end, label %for.body.preheader
Expand Down Expand Up @@ -79,6 +95,21 @@ define void @weakcrossing1(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing1'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - flow [<>] splitable!
; CHECK-SIV-ONLY-NEXT: da analyze - split level = 1, iteration = 0!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
%cmp1 = icmp eq i64 %n, 0
br i1 %cmp1, label %for.end, label %for.body.preheader
Expand Down Expand Up @@ -130,6 +161,20 @@ define void @weakcrossing2(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing2'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
br label %for.body

Expand Down Expand Up @@ -172,6 +217,20 @@ define void @weakcrossing3(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing3'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - flow [0|<]!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
br label %for.body

Expand Down Expand Up @@ -214,6 +273,20 @@ define void @weakcrossing4(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing4'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
br label %for.body

Expand Down Expand Up @@ -256,6 +329,20 @@ define void @weakcrossing5(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %1, ptr %B.addr.02, align 4 --> Dst: store i32 %1, ptr %B.addr.02, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing5'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %1 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %1, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %1 = load i32, ptr %arrayidx2, align 4 --> Dst: %1 = load i32, ptr %arrayidx2, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %1 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %1, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %1, ptr %B.addr.02, align 4 --> Dst: store i32 %1, ptr %B.addr.02, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
%cmp1 = icmp eq i64 %n, 0
br i1 %cmp1, label %for.end, label %for.body.preheader
Expand Down Expand Up @@ -308,6 +395,21 @@ define void @weakcrossing6(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing6'
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - flow [<>] splitable!
; CHECK-SIV-ONLY-NEXT: da analyze - split level = 1, iteration = 2!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: %0 = load i32, ptr %arrayidx1, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: %0 = load i32, ptr %arrayidx1, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - confused!
; CHECK-SIV-ONLY-NEXT: Src: store i32 %0, ptr %B.addr.01, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
br label %for.body

Expand All @@ -329,3 +431,125 @@ for.body: ; preds = %entry, %for.body
for.end: ; preds = %for.body
ret void
}

;; max_i = INT64_MAX/3 // 3074457345618258602
;; for (long long i = 0; i <= max_i; i++) {
;; A[-3*i + INT64_MAX] = 0;
;; if (i)
;; A[3*i - 2] = 1;
;; }
;;
;; FIXME: DependencyAnalsysis currently detects no dependency between
;; `A[-3*i + INT64_MAX]` and `A[3*i - 2]`, but it does exist. For example,
;;
;; memory location | -3*i + INT64_MAX | 3*i - 2
;; ------------------|------------------|-----------
;; A[1] | i = max_i | i = 1
;; A[INT64_MAX - 3] | i = 1 | i = max_i
;;
;; Actually,
;; * 1 = -3*max_i + INT64_MAX = 3*1 - 2
;; * 9223372036854775804 = -3*1 + INT64_MAX = 3*max_i - 2
;;

define void @weakcrossing7(ptr %A) {
; CHECK-LABEL: 'weakcrossing7'
; CHECK-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing7'
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
br label %loop.header

loop.header:
%i = phi i64 [ 0, %entry ], [ %i.inc, %loop.latch ]
%subscript.0 = phi i64 [ 9223372036854775807, %entry ], [ %subscript.0.next, %loop.latch ]
%subscript.1 = phi i64 [ -2, %entry ], [ %subscript.1.next, %loop.latch ]
%idx.0 = getelementptr inbounds i8, ptr %A, i64 %subscript.0
store i8 0, ptr %idx.0
%cond.store = icmp ne i64 %i, 0
br i1 %cond.store, label %if.store, label %loop.latch

if.store:
%idx.1 = getelementptr inbounds i8, ptr %A, i64 %subscript.1
store i8 1, ptr %idx.1
br label %loop.latch

loop.latch:
%i.inc = add nuw nsw i64 %i, 1
%subscript.0.next = add nsw i64 %subscript.0, -3
%subscript.1.next = add nsw i64 %subscript.1, 3
%exitcond = icmp sgt i64 %i.inc, 3074457345618258602
br i1 %exitcond, label %exit, label %loop.header

exit:
ret void
}

;; A generalized version of @weakcrossing7.
;;
;; for (long long i = 0; i <= n / 3; i++) {
;; A[-3*i + n] = 0;
;; if (i)
;; A[3*i - 2] = 1;
;; }

define void @weakcrossing8(ptr %A, i64 %n) {
; CHECK-LABEL: 'weakcrossing8'
; CHECK-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-NEXT: da analyze - output [*|<] splitable!
; CHECK-NEXT: da analyze - split level = 1, iteration = ((0 smax (2 + %n)) /u 6)!
; CHECK-NEXT: Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-NEXT: da analyze - none!
;
; CHECK-SIV-ONLY-LABEL: 'weakcrossing8'
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 0, ptr %idx.0, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
; CHECK-SIV-ONLY-NEXT: Src: store i8 0, ptr %idx.0, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - output [*|<] splitable!
; CHECK-SIV-ONLY-NEXT: da analyze - split level = 1, iteration = ((0 smax (2 + %n)) /u 6)!
; CHECK-SIV-ONLY-NEXT: Src: store i8 1, ptr %idx.1, align 1 --> Dst: store i8 1, ptr %idx.1, align 1
; CHECK-SIV-ONLY-NEXT: da analyze - none!
;
entry:
%bound = sdiv i64 %n, 3
%guard = icmp sgt i64 %n, 0
br i1 %guard, label %loop.header, label %exit

loop.header:
%i = phi i64 [ 0, %entry ], [ %i.inc, %loop.latch ]
%subscript.0 = phi i64 [ %n, %entry ], [ %subscript.0.next, %loop.latch ]
%subscript.1 = phi i64 [ -2, %entry ], [ %subscript.1.next, %loop.latch ]
%idx.0 = getelementptr inbounds i8, ptr %A, i64 %subscript.0
store i8 0, ptr %idx.0
%cond.store = icmp ne i64 %i, 0
br i1 %cond.store, label %if.store, label %loop.latch

if.store:
%idx.1 = getelementptr inbounds i8, ptr %A, i64 %subscript.1
store i8 1, ptr %idx.1
br label %loop.latch

loop.latch:
%i.inc = add nuw nsw i64 %i, 1
%subscript.0.next = add nsw i64 %subscript.0, -3
%subscript.1.next = add nsw i64 %subscript.1, 3
%exitcond = icmp sgt i64 %i.inc, %bound
br i1 %exitcond, label %exit, label %loop.header

exit:
ret void
}
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