[llvm] [DA] Rewrite formula in the Weak Zero SIV tests (PR #183738)
Ryotaro Kasuga via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 6 02:57:23 PST 2026
https://github.com/kasuga-fj updated https://github.com/llvm/llvm-project/pull/183738
>From cd0f762131401fa518e0bfc6dcf18cc87dfc9dca Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
Date: Fri, 27 Feb 2026 12:53:35 +0000
Subject: [PATCH] [DA] Rewrite formula in the Weak Zero SIV tests
---
.../llvm/Analysis/DependenceAnalysis.h | 12 ++--
llvm/lib/Analysis/DependenceAnalysis.cpp | 67 +++++++++----------
.../weak-zero-siv-large-btc.ll | 16 ++---
.../weak-zero-siv-overflow.ll | 8 +--
4 files changed, 45 insertions(+), 58 deletions(-)
diff --git a/llvm/include/llvm/Analysis/DependenceAnalysis.h b/llvm/include/llvm/Analysis/DependenceAnalysis.h
index 6320caf09dd35..b644af3f2ca4a 100644
--- a/llvm/include/llvm/Analysis/DependenceAnalysis.h
+++ b/llvm/include/llvm/Analysis/DependenceAnalysis.h
@@ -561,10 +561,8 @@ class DependenceInfo {
/// Sets appropriate direction entry.
/// Set consistent to false.
/// If loop peeling will break the dependence, mark appropriately.
- bool weakZeroSrcSIVtest(const SCEV *DstCoeff, const SCEV *SrcConst,
- const SCEV *DstConst, const Loop *CurrentSrcLoop,
- const Loop *CurrentDstLoop, unsigned Level,
- FullDependence &Result) const;
+ bool weakZeroSrcSIVtest(const SCEV *SrcConst, const SCEVAddRecExpr *Dst,
+ unsigned Level, FullDependence &Result) const;
/// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
/// (Src and Dst) for dependence.
@@ -576,10 +574,8 @@ class DependenceInfo {
/// Sets appropriate direction entry.
/// Set consistent to false.
/// If loop peeling will break the dependence, mark appropriately.
- bool weakZeroDstSIVtest(const SCEV *SrcCoeff, const SCEV *SrcConst,
- const SCEV *DstConst, const Loop *CurrentSrcLoop,
- const Loop *CurrentDstLoop, unsigned Level,
- FullDependence &Result) const;
+ bool weakZeroDstSIVtest(const SCEVAddRecExpr *Src, const SCEV *DstConst,
+ unsigned Level, FullDependence &Result) const;
/// exactRDIVtest - Tests the RDIV subscript pair for dependence.
/// Things of the form [c1 + a*i] and [c2 + b*j],
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index a9f436c0d32a7..c4940fea46e5e 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -1810,11 +1810,9 @@ static bool isRemainderZero(const SCEVConstant *Dividend,
// (see also weakZeroDstSIVtest)
//
// Return true if dependence disproved.
-bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *DstCoeff,
- const SCEV *SrcConst,
- const SCEV *DstConst,
- const Loop *CurSrcLoop,
- const Loop *CurDstLoop, unsigned Level,
+bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *SrcConst,
+ const SCEVAddRecExpr *Dst,
+ unsigned Level,
FullDependence &Result) const {
if (!isDependenceTestEnabled(DependenceTestType::WeakZeroSIV))
return false;
@@ -1822,6 +1820,8 @@ bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *DstCoeff,
// For the WeakSIV test, it's possible the loop isn't common to
// the Src and Dst loops. If it isn't, then there's no need to
// record a direction.
+ const SCEV *DstCoeff = Dst->getStepRecurrence(*SE);
+ const SCEV *DstConst = Dst->getStart();
LLVM_DEBUG(dbgs() << "\tWeak-Zero (src) SIV test\n");
LLVM_DEBUG(dbgs() << "\t DstCoeff = " << *DstCoeff << "\n");
LLVM_DEBUG(dbgs() << "\t SrcConst = " << *SrcConst << "\n");
@@ -1829,6 +1829,15 @@ bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *DstCoeff,
++WeakZeroSIVapplications;
assert(0 < Level && Level <= MaxLevels && "Level out of range");
Level--;
+
+ ConstantRange SrcRange = SE->getSignedRange(SrcConst);
+ ConstantRange DstRange = SE->getSignedRange(Dst);
+ if (SrcRange.intersectWith(DstRange).isEmptySet()) {
+ ++WeakZeroSIVindependence;
+ ++WeakZeroSIVsuccesses;
+ return true;
+ }
+
const SCEV *Delta = SE->getMinusSCEV(SrcConst, DstConst);
LLVM_DEBUG(dbgs() << "\t Delta = " << *Delta << "\n");
if (SrcConst == DstConst && SE->isKnownNonZero(DstCoeff)) {
@@ -1850,17 +1859,10 @@ bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *DstCoeff,
const SCEV *NewDelta =
SE->isKnownNegative(ConstCoeff) ? SE->getNegativeSCEV(Delta) : Delta;
- // check that Delta/SrcCoeff < iteration count
- // really check NewDelta < count*AbsCoeff
if (const SCEV *UpperBound =
- collectUpperBound(CurSrcLoop, Delta->getType())) {
+ collectUpperBound(Dst->getLoop(), Delta->getType())) {
LLVM_DEBUG(dbgs() << "\t UpperBound = " << *UpperBound << "\n");
const SCEV *Product = SE->getMulExpr(AbsCoeff, UpperBound);
- if (SE->isKnownPredicate(CmpInst::ICMP_SGT, NewDelta, Product)) {
- ++WeakZeroSIVindependence;
- ++WeakZeroSIVsuccesses;
- return true;
- }
if (SE->isKnownPredicate(CmpInst::ICMP_EQ, NewDelta, Product)) {
// dependences caused by last iteration
if (Level < CommonLevels) {
@@ -1921,17 +1923,16 @@ bool DependenceInfo::weakZeroSrcSIVtest(const SCEV *DstCoeff,
// (see also weakZeroSrcSIVtest)
//
// Return true if dependence disproved.
-bool DependenceInfo::weakZeroDstSIVtest(const SCEV *SrcCoeff,
- const SCEV *SrcConst,
- const SCEV *DstConst,
- const Loop *CurSrcLoop,
- const Loop *CurDstLoop, unsigned Level,
+bool DependenceInfo::weakZeroDstSIVtest(const SCEVAddRecExpr *Src,
+ const SCEV *DstConst, unsigned Level,
FullDependence &Result) const {
if (!isDependenceTestEnabled(DependenceTestType::WeakZeroSIV))
return false;
// For the WeakSIV test, it's possible the loop isn't common to the
// Src and Dst loops. If it isn't, then there's no need to record a direction.
+ const SCEV *SrcCoeff = Src->getStepRecurrence(*SE);
+ const SCEV *SrcConst = Src->getStart();
LLVM_DEBUG(dbgs() << "\tWeak-Zero (dst) SIV test\n");
LLVM_DEBUG(dbgs() << "\t SrcCoeff = " << *SrcCoeff << "\n");
LLVM_DEBUG(dbgs() << "\t SrcConst = " << *SrcConst << "\n");
@@ -1939,6 +1940,15 @@ bool DependenceInfo::weakZeroDstSIVtest(const SCEV *SrcCoeff,
++WeakZeroSIVapplications;
assert(0 < Level && Level <= SrcLevels && "Level out of range");
Level--;
+
+ ConstantRange SrcRange = SE->getSignedRange(Src);
+ ConstantRange DstRange = SE->getSignedRange(DstConst);
+ if (SrcRange.intersectWith(DstRange).isEmptySet()) {
+ ++WeakZeroSIVindependence;
+ ++WeakZeroSIVsuccesses;
+ return true;
+ }
+
const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
LLVM_DEBUG(dbgs() << "\t Delta = " << *Delta << "\n");
if (DstConst == SrcConst && SE->isKnownNonZero(SrcCoeff)) {
@@ -1960,17 +1970,10 @@ bool DependenceInfo::weakZeroDstSIVtest(const SCEV *SrcCoeff,
const SCEV *NewDelta =
SE->isKnownNegative(ConstCoeff) ? SE->getNegativeSCEV(Delta) : Delta;
- // check that Delta/SrcCoeff < iteration count
- // really check NewDelta < count*AbsCoeff
if (const SCEV *UpperBound =
- collectUpperBound(CurSrcLoop, Delta->getType())) {
+ collectUpperBound(Src->getLoop(), Delta->getType())) {
LLVM_DEBUG(dbgs() << "\t UpperBound = " << *UpperBound << "\n");
const SCEV *Product = SE->getMulExpr(AbsCoeff, UpperBound);
- if (SE->isKnownPredicate(CmpInst::ICMP_SGT, NewDelta, Product)) {
- ++WeakZeroSIVindependence;
- ++WeakZeroSIVsuccesses;
- return true;
- }
if (SE->isKnownPredicate(CmpInst::ICMP_EQ, NewDelta, Product)) {
// dependences caused by last iteration
if (Level < CommonLevels) {
@@ -2300,23 +2303,15 @@ bool DependenceInfo::testSIV(const SCEV *Src, const SCEV *Dst, unsigned &Level,
CurDstLoop);
}
if (SrcAddRec) {
- const SCEV *SrcConst = SrcAddRec->getStart();
- const SCEV *SrcCoeff = SrcAddRec->getStepRecurrence(*SE);
- const SCEV *DstConst = Dst;
const Loop *CurSrcLoop = SrcAddRec->getLoop();
Level = mapSrcLoop(CurSrcLoop);
- return weakZeroDstSIVtest(SrcCoeff, SrcConst, DstConst, CurSrcLoop,
- CurSrcLoop, Level, Result) ||
+ return weakZeroDstSIVtest(SrcAddRec, Dst, Level, Result) ||
gcdMIVtest(Src, Dst, Result);
}
if (DstAddRec) {
- const SCEV *DstConst = DstAddRec->getStart();
- const SCEV *DstCoeff = DstAddRec->getStepRecurrence(*SE);
- const SCEV *SrcConst = Src;
const Loop *CurDstLoop = DstAddRec->getLoop();
Level = mapDstLoop(CurDstLoop);
- return weakZeroSrcSIVtest(DstCoeff, SrcConst, DstConst, CurDstLoop,
- CurDstLoop, Level, Result) ||
+ return weakZeroSrcSIVtest(Src, DstAddRec, Level, Result) ||
gcdMIVtest(Src, Dst, Result);
}
llvm_unreachable("SIV test expected at least one AddRec");
diff --git a/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-large-btc.ll b/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-large-btc.ll
index 144efa45ed2cb..e5aa0cac5a6e3 100644
--- a/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-large-btc.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-large-btc.ll
@@ -10,15 +10,15 @@
; A[0] = 1;
; }
;
-; FIXME: `A[i] = 0` will be executed (when i == 0), so there is a ; dependency
-; between the ; two stores.
+; `A[i] = 0` will be executed (when i == 0), so there is a dependency between
+; the two stores.
;
define void @weak_zero_src_siv_large_btc(ptr %A) {
; CHECK-ALL-LABEL: 'weak_zero_src_siv_large_btc'
; CHECK-ALL-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 0, ptr %gep, align 1
; CHECK-ALL-NEXT: da analyze - none!
; CHECK-ALL-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 1, ptr %A, align 1
-; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: da analyze - output [*|<]!
; CHECK-ALL-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 1, ptr %A, align 1
; CHECK-ALL-NEXT: da analyze - output [S]!
;
@@ -26,7 +26,7 @@ define void @weak_zero_src_siv_large_btc(ptr %A) {
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 0, ptr %gep, align 1
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [*]!
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 1, ptr %A, align 1
-; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - none!
+; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [*|<]!
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 1, ptr %A, align 1
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [S]!
;
@@ -60,15 +60,15 @@ exit:
; A[i] = 0;
; }
;
-; FIXME: `A[i] = 0` will be executed (when i == 0), so there is a ; dependency
-; between the ; two stores.
+; `A[i] = 0` will be executed (when i == 0), so there is a dependency between
+; the two stores.
;
define void @weak_zero_dst_siv_large_btc(ptr %A) {
; CHECK-ALL-LABEL: 'weak_zero_dst_siv_large_btc'
; CHECK-ALL-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 1, ptr %A, align 1
; CHECK-ALL-NEXT: da analyze - output [S]!
; CHECK-ALL-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 0, ptr %gep, align 1
-; CHECK-ALL-NEXT: da analyze - none!
+; CHECK-ALL-NEXT: da analyze - output [*|<]!
; CHECK-ALL-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 0, ptr %gep, align 1
; CHECK-ALL-NEXT: da analyze - none!
;
@@ -76,7 +76,7 @@ define void @weak_zero_dst_siv_large_btc(ptr %A) {
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 1, ptr %A, align 1
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [S]!
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 1, ptr %A, align 1 --> Dst: store i8 0, ptr %gep, align 1
-; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - none!
+; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [*|<]!
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: Src: store i8 0, ptr %gep, align 1 --> Dst: store i8 0, ptr %gep, align 1
; CHECK-WEAK-ZERO-SRC-SIV-NEXT: da analyze - output [*]!
;
diff --git a/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-overflow.ll b/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-overflow.ll
index f388502ac2a43..63a295cca35cd 100644
--- a/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-overflow.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/weak-zero-siv-overflow.ll
@@ -10,16 +10,12 @@
; A[2] = 2;
; }
;
-; FIXME: DependenceAnalysis currently detects no dependency between the two
-; stores, but it does exist. The root cause is that the product of the BTC and
-; the coefficient ((1LL << 62) - 1 and 2) overflows in a signed sense.
-;
define void @weakzero_dst_siv_prod_ovfl(ptr %A) {
; CHECK-ALL-LABEL: 'weakzero_dst_siv_prod_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: da analyze - output [*|<]!
; 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 - output [S]!
;
@@ -27,7 +23,7 @@ define void @weakzero_dst_siv_prod_ovfl(ptr %A) {
; CHECK-WEAK-ZERO-SIV-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
; CHECK-WEAK-ZERO-SIV-NEXT: da analyze - output [*]!
; CHECK-WEAK-ZERO-SIV-NEXT: Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
-; CHECK-WEAK-ZERO-SIV-NEXT: da analyze - none!
+; CHECK-WEAK-ZERO-SIV-NEXT: da analyze - output [*|<]!
; CHECK-WEAK-ZERO-SIV-NEXT: Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
; CHECK-WEAK-ZERO-SIV-NEXT: da analyze - output [S]!
;
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