[llvm] 1b3e7df - [DA] Check for overflow in strong SIV test (#164704)
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Fri Oct 31 10:19:25 PDT 2025
Author: Alireza Torabian
Date: 2025-10-31T13:19:20-04:00
New Revision: 1b3e7df195f4900a858e97a887e47eddd6dabdfe
URL: https://github.com/llvm/llvm-project/commit/1b3e7df195f4900a858e97a887e47eddd6dabdfe
DIFF: https://github.com/llvm/llvm-project/commit/1b3e7df195f4900a858e97a887e47eddd6dabdfe.diff
LOG: [DA] Check for overflow in strong SIV test (#164704)
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`.
Added:
Modified:
llvm/lib/Analysis/DependenceAnalysis.cpp
llvm/test/Analysis/DependenceAnalysis/SimpleSIVNoValidityCheck.ll
llvm/test/Analysis/DependenceAnalysis/StrongSIV.ll
Removed:
################################################################################
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 44bd9b7727910..160196284f415 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 +528,45 @@ 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 fails to detect the dependency between A[i] and
+; itself, while Strong SIV has been able to prove it.
+define void @strong11(ptr %A) nounwind uwtable ssp {
+; 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
+
+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
+}
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