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[DA] Set Distance to zero when Direction is EQ #147966

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kasuga-fj merged 5 commits into from
Jul 11, 2025
Merged

[DA] Set Distance to zero when Direction is EQ #147966

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ad3f5e9
[DA] Set Distance to zero when Direction is EQ
kasuga-fj Jul 10, 2025
c3338ba
Apply suggestions from code review
kasuga-fj Jul 10, 2025
20d5661
Add assert for the cases where distance is non-zero and direction is EQ
kasuga-fj Jul 10, 2025
2a8f9c8
Fix typo
kasuga-fj Jul 10, 2025
dcb6679
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kasuga-fj Jul 10, 2025
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29 changes: 29 additions & 0 deletions llvm/lib/Analysis/DependenceAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,18 @@ static void dumpExampleDependence(raw_ostream &OS, DependenceInfo *DA,
OS << " da analyze - ";
if (auto D = DA->depends(&*SrcI, &*DstI,
/*UnderRuntimeAssumptions=*/true)) {

// Verify that the distance begin zero is equivalent to the
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@madhur13490 madhur13490 Jul 10, 2025

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s/begin/being?

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@kasuga-fj kasuga-fj Jul 10, 2025

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Yes, thanks

// direction being EQ.
for (unsigned Level = 1; Level <= D->getLevels(); Level++) {
const SCEV *Distance = D->getDistance(Level);
bool IsDistanceZero = Distance && Distance->isZero();
bool IsDirectionEQ =
D->getDirection(Level) == Dependence::DVEntry::EQ;
assert(IsDistanceZero == IsDirectionEQ &&
"Inconsistent distance and direction.");
}

// Normalize negative direction vectors if required by clients.
if (NormalizeResults && D->normalize(&SE))
OS << "normalized - ";
Expand Down Expand Up @@ -3991,6 +4003,23 @@ DependenceInfo::depends(Instruction *Src, Instruction *Dst,
if (CompleteLoops[II])
Result.DV[II - 1].Scalar = false;

// Set the distance to zero if the direction is EQ.
// TODO: Ideally, the distance should be set to 0 immediately simultaneously
// with the corresponding direction being set to EQ.
for (unsigned II = 1; II <= Result.getLevels(); ++II) {
if (Result.getDirection(II) == Dependence::DVEntry::EQ)
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@Meinersbur Meinersbur Jul 10, 2025

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Is it only that Distance is nullptr, or are there cases where it is non-zero but direction is still EQ?

In the former case, could you set the direction only when Distance is nullptr and assert if not SCEV::isZero?

In the latter case, the would be something quite wrong. Why prioritize the Direction analysis result over the Distance?

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@kasuga-fj kasuga-fj Jul 10, 2025

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The former. I noticed it when I changed the code a bit and saw that some of the dumped results in the tests changed from = to 0. Added assert for the latter case.

Result.DV[II - 1].Distance = SE->getZero(SrcSCEV->getType());

LLVM_DEBUG({
// Check that the converse (i.e., if the distance is zero, then the
// direction is EQ) holds.
const SCEV *Distance = Result.getDistance(II);
if (Distance && Distance->isZero())
assert(Result.getDirection(II) == Dependence::DVEntry::EQ &&
"Distance is zero, but direction is not EQ");
});
}

if (PossiblyLoopIndependent) {
// Make sure the LoopIndependent flag is set correctly.
// All directions must include equal, otherwise no
Expand Down
18 changes: 9 additions & 9 deletions llvm/test/Analysis/DependenceAnalysis/Banerjee.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -802,7 +802,7 @@ define void @banerjee9(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; CHECK-NEXT: da analyze - output [* *]!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
; CHECK-NEXT: da analyze - flow [<= =|<]!
; CHECK-NEXT: da analyze - flow [<= 0|<]!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %1 = load i64, ptr %arrayidx7, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
Expand All @@ -816,7 +816,7 @@ define void @banerjee9(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; NORMALIZE-NEXT: da analyze - output [* *]!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
; NORMALIZE-NEXT: da analyze - flow [<= =|<]!
; NORMALIZE-NEXT: da analyze - flow [<= 0|<]!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; NORMALIZE-NEXT: da analyze - confused!
; NORMALIZE-NEXT: Src: %1 = load i64, ptr %arrayidx7, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
Expand All @@ -830,7 +830,7 @@ define void @banerjee9(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; DELIN-NEXT: da analyze - output [* *]!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
; DELIN-NEXT: da analyze - flow [<= =|<]!
; DELIN-NEXT: da analyze - flow [<= 0|<]!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; DELIN-NEXT: da analyze - confused!
; DELIN-NEXT: Src: %1 = load i64, ptr %arrayidx7, align 8 --> Dst: %1 = load i64, ptr %arrayidx7, align 8
Expand Down Expand Up @@ -888,7 +888,7 @@ define void @banerjee10(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
; CHECK-NEXT: da analyze - flow [<> =]!
; CHECK-NEXT: da analyze - flow [<> 0]!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %1 = load i64, ptr %arrayidx6, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
Expand All @@ -902,7 +902,7 @@ define void @banerjee10(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; NORMALIZE-NEXT: da analyze - none!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
; NORMALIZE-NEXT: da analyze - flow [<> =]!
; NORMALIZE-NEXT: da analyze - flow [<> 0]!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; NORMALIZE-NEXT: da analyze - confused!
; NORMALIZE-NEXT: Src: %1 = load i64, ptr %arrayidx6, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
Expand All @@ -916,7 +916,7 @@ define void @banerjee10(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; DELIN-NEXT: da analyze - none!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
; DELIN-NEXT: da analyze - flow [<> =]!
; DELIN-NEXT: da analyze - flow [<> 0]!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %1, ptr %B.addr.11, align 8
; DELIN-NEXT: da analyze - confused!
; DELIN-NEXT: Src: %1 = load i64, ptr %arrayidx6, align 8 --> Dst: %1 = load i64, ptr %arrayidx6, align 8
Expand Down Expand Up @@ -1058,7 +1058,7 @@ define void @banerjee12(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
; CHECK-NEXT: da analyze - flow [= <>]!
; CHECK-NEXT: da analyze - flow [0 <>]!
; CHECK-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %0, ptr %B.addr.11, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load i64, ptr %arrayidx6, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
Expand All @@ -1072,7 +1072,7 @@ define void @banerjee12(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; NORMALIZE-NEXT: da analyze - none!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
; NORMALIZE-NEXT: da analyze - flow [= <>]!
; NORMALIZE-NEXT: da analyze - flow [0 <>]!
; NORMALIZE-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %0, ptr %B.addr.11, align 8
; NORMALIZE-NEXT: da analyze - confused!
; NORMALIZE-NEXT: Src: %0 = load i64, ptr %arrayidx6, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
Expand All @@ -1086,7 +1086,7 @@ define void @banerjee12(ptr %A, ptr %B, i64 %m, i64 %n) nounwind uwtable ssp {
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 0, ptr %arrayidx, align 8
; DELIN-NEXT: da analyze - none!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
; DELIN-NEXT: da analyze - flow [= <>]!
; DELIN-NEXT: da analyze - flow [0 <>]!
; DELIN-NEXT: Src: store i64 0, ptr %arrayidx, align 8 --> Dst: store i64 %0, ptr %B.addr.11, align 8
; DELIN-NEXT: da analyze - confused!
; DELIN-NEXT: Src: %0 = load i64, ptr %arrayidx6, align 8 --> Dst: %0 = load i64, ptr %arrayidx6, align 8
Expand Down
6 changes: 3 additions & 3 deletions llvm/test/Analysis/DependenceAnalysis/Coupled.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -285,7 +285,7 @@ define void @couple6(ptr %A, ptr %B, i32 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx1, align 4 --> Dst: store i32 %conv, ptr %arrayidx1, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx1, align 4 --> Dst: %0 = load i32, ptr %arrayidx3, align 4
; CHECK-NEXT: da analyze - flow [=|<]!
; CHECK-NEXT: da analyze - flow [0|<]!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx1, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load i32, ptr %arrayidx3, align 4 --> Dst: %0 = load i32, ptr %arrayidx3, align 4
Expand Down Expand Up @@ -503,7 +503,7 @@ define void @couple11(ptr %A, ptr %B, i32 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx2, align 4 --> Dst: store i32 %conv, ptr %arrayidx2, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx2, align 4 --> Dst: %0 = load i32, ptr %arrayidx4, align 4
; CHECK-NEXT: da analyze - flow [=|<] splitable!
; CHECK-NEXT: da analyze - flow [0|<] splitable!
; CHECK-NEXT: da analyze - split level = 1, iteration = 9!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx2, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - confused!
Expand Down Expand Up @@ -636,7 +636,7 @@ define void @couple14(ptr %A, ptr %B, i32 %n) nounwind uwtable ssp {
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx3, align 4 --> Dst: store i32 %conv, ptr %arrayidx3, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx3, align 4 --> Dst: %0 = load i32, ptr %arrayidx6, align 4
; CHECK-NEXT: da analyze - flow [=|<]!
; CHECK-NEXT: da analyze - flow [0|<]!
; CHECK-NEXT: Src: store i32 %conv, ptr %arrayidx3, align 4 --> Dst: store i32 %0, ptr %B.addr.01, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load i32, ptr %arrayidx6, align 4 --> Dst: %0 = load i32, ptr %arrayidx6, align 4
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll
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Expand Up @@ -18,7 +18,7 @@ define void @i32_subscript(ptr %a, ptr %b) {
; CHECK-NEXT: Src: %0 = load i32, ptr %a.addr, align 4 --> Dst: %0 = load i32, ptr %a.addr, align 4
; CHECK-NEXT: da analyze - none!
; CHECK-NEXT: Src: %0 = load i32, ptr %a.addr, align 4 --> Dst: store i32 %1, ptr %a.addr.2, align 4
; CHECK-NEXT: da analyze - anti [=|<]!
; CHECK-NEXT: da analyze - anti [0|<]!
; CHECK-NEXT: Src: store i32 %1, ptr %a.addr.2, align 4 --> Dst: store i32 %1, ptr %a.addr.2, align 4
; CHECK-NEXT: da analyze - none!
;
Expand Down
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