[llvm] [DA] Set Distance to zero when Direction is EQ (PR #147966)
Ryotaro Kasuga via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 10 06:51:30 PDT 2025
https://github.com/kasuga-fj created https://github.com/llvm/llvm-project/pull/147966
A dependence object has two entries: Distance and Direction. The former represents the distance of the dependence, while the latter characterizes the distance by whether the value of it is positive, negative, or zero (especially, zero is represented by EQ in DA). So it is expected that the Distance equals zero iff the Direction is EQ. However, this condition was not satisfied in some cases.
This patch adds a logic to set the Distance to zero if the Direction is EQ. Although it is ideal that the Distance is updated to zero simultaneously when the Direction is set to EQ, achieving it would require changing the entire code in DA.
>From ad3f5e94b9b6bf9c2f92ae1f50cefdc509b91c15 Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
Date: Thu, 10 Jul 2025 13:20:16 +0000
Subject: [PATCH] [DA] Set Distance to zero when Direction is EQ
---
llvm/lib/Analysis/DependenceAnalysis.cpp | 29 +++++++++++++++++++
.../Analysis/DependenceAnalysis/Banerjee.ll | 18 ++++++------
.../Analysis/DependenceAnalysis/Coupled.ll | 6 ++--
.../NonCanonicalizedSubscript.ll | 2 +-
4 files changed, 42 insertions(+), 13 deletions(-)
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 5b85060f9caa1..df5fd0e938707 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -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
+ // 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 - ";
@@ -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)
+ 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
diff --git a/llvm/test/Analysis/DependenceAnalysis/Banerjee.ll b/llvm/test/Analysis/DependenceAnalysis/Banerjee.ll
index 6768e9067dca3..d3301520fd107 100644
--- a/llvm/test/Analysis/DependenceAnalysis/Banerjee.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/Banerjee.ll
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
diff --git a/llvm/test/Analysis/DependenceAnalysis/Coupled.ll b/llvm/test/Analysis/DependenceAnalysis/Coupled.ll
index ff9f393f88152..06bfc5d2e8573 100644
--- a/llvm/test/Analysis/DependenceAnalysis/Coupled.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/Coupled.ll
@@ -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
@@ -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!
@@ -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
diff --git a/llvm/test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll b/llvm/test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll
index f0cd2fd4cd930..e5d5d21e365a1 100644
--- a/llvm/test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll
@@ -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!
;
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