[llvm] [DA] Check for overflow in strong SIV test (PR #166223)
Alireza Torabian via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 6 09:10:51 PST 2025
https://github.com/1997alireza updated https://github.com/llvm/llvm-project/pull/166223
>From 2b021e4ee195ba54edeae3785ebdbb2e6be20fe3 Mon Sep 17 00:00:00 2001
From: Alireza Torabian <alireza.torabian at huawei.com>
Date: Tue, 28 Oct 2025 18:04:28 -0400
Subject: [PATCH 1/2] [DA] Adding a test case failure due to overflow in strong
SIV test
---
.../Analysis/DependenceAnalysis/StrongSIV.ll | 82 +++++++++++++++----
1 file changed, 68 insertions(+), 14 deletions(-)
diff --git a/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll b/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
index 44bd9b7727910..d585d88e4285c 100644
--- a/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
@@ -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: | FileCheck %s --check-prefixes=CHECK,CHECK-ALL
+; RUN: opt < %s -disable-output "-passes=print<da>" -aa-pipeline=basic-aa -da-enable-dependence-test=strong-siv 2>&1 \
+; RUN: | FileCheck %s --check-prefixes=CHECK,CHECK-STRONG-SIV
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"
target triple = "x86_64-apple-macosx10.6.0"
@@ -423,19 +425,33 @@ for.end: ; preds = %for.body
;; *B++ = A[i + 2*n];
define void @strong9(ptr %A, ptr %B, i64 %n) nounwind uwtable ssp {
-; CHECK-LABEL: 'strong9'
-; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
-; CHECK-NEXT: da analyze - none!
-; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
-; CHECK-NEXT: da analyze - none!
-; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
-; CHECK-NEXT: da analyze - confused!
-; CHECK-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
-; CHECK-NEXT: da analyze - none!
-; CHECK-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
-; CHECK-NEXT: da analyze - confused!
-; 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-ALL-LABEL: 'strong9'
+; CHECK-ALL-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
+; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
+; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-ALL-NEXT: da analyze - confused!
+; CHECK-ALL-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
+; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-ALL-NEXT: da analyze - confused!
+; CHECK-ALL-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-ALL-NEXT: da analyze - none!
+;
+; CHECK-STRONG-SIV-LABEL: 'strong9'
+; CHECK-STRONG-SIV-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %conv, ptr %arrayidx, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - none!
+; CHECK-STRONG-SIV-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - flow [*|<]!
+; CHECK-STRONG-SIV-NEXT: Src: store i32 %conv, ptr %arrayidx, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - confused!
+; CHECK-STRONG-SIV-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx2, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - none!
+; CHECK-STRONG-SIV-NEXT: Src: %0 = load i32, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - confused!
+; CHECK-STRONG-SIV-NEXT: Src: store i32 %0, ptr %B.addr.02, align 4 --> Dst: store i32 %0, ptr %B.addr.02, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - none!
;
entry:
%cmp1 = icmp eq i64 %n, 0
@@ -512,3 +528,41 @@ for.body: ; preds = %entry, %for.body
for.end: ; preds = %for.body
ret void
}
+
+
+;; for (long unsigned i = 0; i < 9223372036854775806; i++)
+;; for (long unsigned j = 0; j < 2147483640; j++)
+;; if (i < 3000000000)
+;; A[i] = 0;
+;
+; FIXME: DependenceAnalysis currently detects no dependency between A[i] and
+; itself, but it does exist.
+define void @strong11(ptr %A) nounwind uwtable ssp {
+; CHECK-LABEL: 'strong11'
+; CHECK-NEXT: Src: store i32 0, ptr %arrayidx, align 4 --> Dst: store i32 0, ptr %arrayidx, align 4
+; CHECK-NEXT: da analyze - none!
+;
+entry:
+ br label %for.cond1.preheader
+
+for.cond1.preheader: ; preds = %entry, %for.cond.cleanup3
+ %i.017 = phi i64 [ 0, %entry ], [ %inc8, %for.cond.cleanup3 ]
+ %cmp5 = icmp samesign ult i64 %i.017, 3000000000
+ %arrayidx = getelementptr inbounds nuw i32, ptr %A, i64 %i.017
+ br i1 %cmp5, label %for.body4.us, label %for.cond.cleanup3
+
+for.body4.us: ; preds = %for.cond1.preheader, %for.body4.us
+ %j.016.us = phi i64 [ %inc.us, %for.body4.us ], [ 0, %for.cond1.preheader ]
+ store i32 0, ptr %arrayidx, align 4
+ %inc.us = add nuw nsw i64 %j.016.us, 1
+ %exitcond.not = icmp eq i64 %inc.us, 2147483640
+ br i1 %exitcond.not, label %for.cond.cleanup3, label %for.body4.us
+
+for.cond.cleanup: ; preds = %for.cond.cleanup3
+ ret void
+
+for.cond.cleanup3: ; preds = %for.body4.us, %for.cond1.preheader
+ %inc8 = add nuw nsw i64 %i.017, 1
+ %exitcond19.not = icmp eq i64 %inc8, 9223372036854775806
+ br i1 %exitcond19.not, label %for.cond.cleanup, label %for.cond1.preheader
+}
>From 4c2ba55562d47f0370340e2d1cf7ac4ff462010b Mon Sep 17 00:00:00 2001
From: Alireza Torabian <alireza.torabian at huawei.com>
Date: Wed, 22 Oct 2025 15:41:15 -0400
Subject: [PATCH 2/2] [DA] Check for overflow in strong SIV test
Rely on the product of `UpperBound` and `AbsCoeff` only if SCEV
can prove that there is no overflow. Also the same about the result
of the subtraction of `DstConst` from `SrcConst` to calculate `Delta`.
---
llvm/lib/Analysis/DependenceAnalysis.cpp | 19 +++++++++--
.../SimpleSIVNoValidityCheck.ll | 2 +-
.../Analysis/DependenceAnalysis/StrongSIV.ll | 14 +++++---
.../DependenceAnalysis/strong-siv-overflow.ll | 32 +++++++++++--------
4 files changed, 45 insertions(+), 22 deletions(-)
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 11d829492a10e..e45d1f79b3165 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -1587,6 +1587,15 @@ static const SCEV *minusSCEVNoSignedOverflow(const SCEV *A, const SCEV *B,
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 *mulSCEVNoSignedOverflow(const SCEV *A, const SCEV *B,
+ ScalarEvolution &SE) {
+ if (SE.willNotOverflow(Instruction::Mul, /*Signed=*/true, A, B))
+ return SE.getMulExpr(A, B);
+ return nullptr;
+}
+
/// Returns the absolute value of \p A. In the context of dependence analysis,
/// we need an absolute value in a mathematical sense. If \p A is the signed
/// minimum value, we cannot represent it unless extending the original type.
@@ -1686,7 +1695,11 @@ bool DependenceInfo::strongSIVtest(const SCEV *Coeff, const SCEV *SrcConst,
assert(0 < Level && Level <= CommonLevels && "level out of range");
Level--;
- const SCEV *Delta = SE->getMinusSCEV(SrcConst, DstConst);
+ const SCEV *Delta = minusSCEVNoSignedOverflow(SrcConst, DstConst, *SE);
+ if (!Delta) {
+ Result.Consistent = false;
+ return false;
+ }
LLVM_DEBUG(dbgs() << "\t Delta = " << *Delta);
LLVM_DEBUG(dbgs() << ", " << *Delta->getType() << "\n");
@@ -1702,7 +1715,9 @@ bool DependenceInfo::strongSIVtest(const SCEV *Coeff, const SCEV *SrcConst,
const SCEV *AbsCoeff = absSCEVNoSignedOverflow(Coeff, *SE);
if (!AbsDelta || !AbsCoeff)
return false;
- const SCEV *Product = SE->getMulExpr(UpperBound, AbsCoeff);
+ const SCEV *Product = mulSCEVNoSignedOverflow(UpperBound, AbsCoeff, *SE);
+ if (!Product)
+ return false;
return isKnownPredicate(CmpInst::ICMP_SGT, AbsDelta, Product);
}();
if (IsDeltaLarge) {
diff --git a/llvm/test/Analysis/DependenceAnalysis/SimpleSIVNoValidityCheck.ll b/llvm/test/Analysis/DependenceAnalysis/SimpleSIVNoValidityCheck.ll
index 4346507ba8f90..181a4494b036e 100644
--- a/llvm/test/Analysis/DependenceAnalysis/SimpleSIVNoValidityCheck.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/SimpleSIVNoValidityCheck.ll
@@ -210,7 +210,7 @@ define void @t3(i64 %n, i64 %m, i64 %lb, ptr %a) {
; CHECK-NEXT: Src: %2 = load i32, ptr %arrayidx6, align 4 --> Dst: %2 = load i32, ptr %arrayidx6, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: %2 = load i32, ptr %arrayidx6, align 4 --> Dst: store i32 %2, ptr %arrayidx8, align 4
-; CHECK-NEXT: da analyze - consistent anti [1 -2]!
+; CHECK-NEXT: da analyze - anti [1 *]!
; CHECK-NEXT: Src: store i32 %2, ptr %arrayidx8, align 4 --> Dst: store i32 %2, ptr %arrayidx8, align 4
; CHECK-NEXT: da analyze - none!
;
diff --git a/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll b/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
index d585d88e4285c..71b93826ac260 100644
--- a/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
@@ -535,12 +535,16 @@ for.end: ; preds = %for.body
;; if (i < 3000000000)
;; A[i] = 0;
;
-; FIXME: DependenceAnalysis currently detects no dependency between A[i] and
-; itself, but it does exist.
+; FIXME: DependenceAnalysis fails to detect the dependency between A[i] and
+; itself, and the issue is not caused by the Strong SIV.
define void @strong11(ptr %A) nounwind uwtable ssp {
-; CHECK-LABEL: 'strong11'
-; CHECK-NEXT: Src: store i32 0, ptr %arrayidx, align 4 --> Dst: store i32 0, ptr %arrayidx, align 4
-; CHECK-NEXT: da analyze - none!
+; CHECK-ALL-LABEL: 'strong11'
+; CHECK-ALL-NEXT: Src: store i32 0, ptr %arrayidx, align 4 --> Dst: store i32 0, ptr %arrayidx, align 4
+; CHECK-ALL-NEXT: da analyze - none!
+;
+; CHECK-STRONG-SIV-LABEL: 'strong11'
+; CHECK-STRONG-SIV-NEXT: Src: store i32 0, ptr %arrayidx, align 4 --> Dst: store i32 0, ptr %arrayidx, align 4
+; CHECK-STRONG-SIV-NEXT: da analyze - consistent output [0 S]!
;
entry:
br label %for.cond1.preheader
diff --git a/llvm/test/Analysis/DependenceAnalysis/strong-siv-overflow.ll b/llvm/test/Analysis/DependenceAnalysis/strong-siv-overflow.ll
index bf0fafcbfd6c9..6fd71ac8fe414 100644
--- a/llvm/test/Analysis/DependenceAnalysis/strong-siv-overflow.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/strong-siv-overflow.ll
@@ -12,19 +12,24 @@
; A[2*i - 4] = 2;
; }
;
-; FIXME: DependenceAnalysis currently detects no dependency between the two
-; stores, but it does exist. For example, each store will access A[0] when i
-; is 1 and 2 respectively.
-; The root cause is that the product of the BTC and the coefficient
-; ((1LL << 62) - 1 and 2) overflows in a signed sense.
+; FIXME: DependenceAnalysis fails to detect the dependency between the two
+; stores, and the issue is not caused by the Strong SIV.
define void @strongsiv_const_ovfl(ptr %A) {
-; CHECK-LABEL: 'strongsiv_const_ovfl'
-; CHECK-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
-; CHECK-NEXT: da analyze - none!
-; CHECK-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
-; CHECK-NEXT: da analyze - none!
-; CHECK-NEXT: Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
-; CHECK-NEXT: da analyze - none!
+; CHECK-ALL-LABEL: 'strongsiv_const_ovfl'
+; CHECK-ALL-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
+; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-ALL-NEXT: da analyze - none!
+;
+; CHECK-STRONG-SIV-LABEL: 'strongsiv_const_ovfl'
+; CHECK-STRONG-SIV-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
+; CHECK-STRONG-SIV-NEXT: da analyze - none!
+; CHECK-STRONG-SIV-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-STRONG-SIV-NEXT: da analyze - consistent output [1]!
+; CHECK-STRONG-SIV-NEXT: Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-STRONG-SIV-NEXT: da analyze - none!
;
entry:
br label %loop.header
@@ -64,5 +69,4 @@ exit:
ret void
}
;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
-; CHECK-ALL: {{.*}}
-; CHECK-STRONG-SIV: {{.*}}
+; CHECK: {{.*}}
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