https://github.com/kasuga-fj created
https://github.com/llvm/llvm-project/pull/148241
None
>From 3596b1726514dda5942d99d4779852e01367c764 Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryot...@fujitsu.com>
Date: Fri, 11 Jul 2025 13:10:44 +0000
Subject: [PATCH] [DA] Add check for base pointer invariance
---
llvm/lib/Analysis/DependenceAnalysis.cpp | 16 ++++++++++++++++
.../DependenceAnalysis/FlipFlopBaseAddress.ll | 18 +++++++++---------
2 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp
b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 428342f51ad2e..07bf560772c8c 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -3383,6 +3383,10 @@ bool DependenceInfo::tryDelinearize(Instruction *Src,
Instruction *Dst,
SrcSubscripts, DstSubscripts))
return false;
+ assert(isLoopInvariant(SrcBase, SrcLoop) &&
+ isLoopInvariant(DstBase, DstLoop) &&
+ "Expected SrcBase and DstBase to be loop invariant");
+
int Size = SrcSubscripts.size();
LLVM_DEBUG({
dbgs() << "\nSrcSubscripts: ";
@@ -3666,6 +3670,18 @@ DependenceInfo::depends(Instruction *Src, Instruction
*Dst,
SCEVUnionPredicate(Assume, *SE));
}
+ // Even if the base pointers are the same, they may not be loop-invariant. It
+ // could lead to incorrect results, as we're analyzing loop-carried
+ // dependencies.
+ Loop *SrcLoop = LI->getLoopFor(Src->getParent());
+ Loop *DstLoop = LI->getLoopFor(Dst->getParent());
+ if (!isLoopInvariant(SrcBase, SrcLoop) ||
+ !isLoopInvariant(DstBase, DstLoop)) {
+ LLVM_DEBUG(dbgs() << "The base pointer is not loop invariant.\n");
+ return std::make_unique<Dependence>(Src, Dst,
+ SCEVUnionPredicate(Assume, *SE));
+ }
+
uint64_t EltSize = SrcLoc.Size.toRaw();
const SCEV *SrcEv = SE->getMinusSCEV(SrcSCEV, SrcBase);
const SCEV *DstEv = SE->getMinusSCEV(DstSCEV, DstBase);
diff --git a/llvm/test/Analysis/DependenceAnalysis/FlipFlopBaseAddress.ll
b/llvm/test/Analysis/DependenceAnalysis/FlipFlopBaseAddress.ll
index 843c18a6e0d1e..a357018563be1 100644
--- a/llvm/test/Analysis/DependenceAnalysis/FlipFlopBaseAddress.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/FlipFlopBaseAddress.ll
@@ -8,11 +8,11 @@
define float @bug41488_test1(float %f) {
; CHECK-LABEL: 'bug41488_test1'
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: %0 = load float,
ptr %p, align 4
-; CHECK-NEXT: da analyze - input [*]!
+; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: store float %f,
ptr %q, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store float %f, ptr %q, align 4 --> Dst: store float %f,
ptr %q, align 4
-; CHECK-NEXT: da analyze - output [*]!
+; CHECK-NEXT: da analyze - confused!
;
entry:
%g = alloca float, align 4
@@ -34,11 +34,11 @@ for.cond.cleanup:
define void @bug41488_test2(i32 %n) {
; CHECK-LABEL: 'bug41488_test2'
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: %0 = load float,
ptr %p, align 4
-; CHECK-NEXT: da analyze - input [*]!
+; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load float, ptr %p, align 4 --> Dst: store float
0.000000e+00, ptr %q, align 4
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store float 0.000000e+00, ptr %q, align 4 --> Dst: store
float 0.000000e+00, ptr %q, align 4
-; CHECK-NEXT: da analyze - output [*]!
+; CHECK-NEXT: da analyze - confused!
;
entry:
%g = alloca float, align 4
@@ -68,7 +68,7 @@ define void @bug53942_foo(i32 noundef %n, ptr noalias
nocapture noundef writeonl
; CHECK-NEXT: Src: %.pre = load double, ptr %B, align 8 --> Dst: store double
%.pre, ptr %arrayidx2, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store double %.pre, ptr %arrayidx2, align 8 --> Dst: store
double %.pre, ptr %arrayidx2, align 8
-; CHECK-NEXT: da analyze - output [*]!
+; CHECK-NEXT: da analyze - confused!
;
entry:
%cmp8 = icmp sgt i32 %n, 1
@@ -99,11 +99,11 @@ for.body: ; preds =
%for.body.preheader,
define void @bug53942_bar(i32 noundef %n, ptr noalias noundef %A, ptr noalias
noundef %B) {
; CHECK-LABEL: 'bug53942_bar'
; CHECK-NEXT: Src: %0 = load double, ptr %arrayidx, align 8 --> Dst: %0 =
load double, ptr %arrayidx, align 8
-; CHECK-NEXT: da analyze - input [*]!
+; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: %0 = load double, ptr %arrayidx, align 8 --> Dst: store
double %0, ptr %arrayidx8, align 8
; CHECK-NEXT: da analyze - confused!
; CHECK-NEXT: Src: store double %0, ptr %arrayidx8, align 8 --> Dst: store
double %0, ptr %arrayidx8, align 8
-; CHECK-NEXT: da analyze - output [*]!
+; CHECK-NEXT: da analyze - confused!
;
entry:
br label %for.cond
@@ -173,7 +173,7 @@ for.end: ; preds =
%for.cond.cleanup
define void @non_invariant_baseptr_with_identical_obj(ptr %A) {
; CHECK-LABEL: 'non_invariant_baseptr_with_identical_obj'
; CHECK-NEXT: Src: store i32 1, ptr %idx, align 4 --> Dst: store i32 1, ptr
%idx, align 4
-; CHECK-NEXT: da analyze - none!
+; CHECK-NEXT: da analyze - confused!
;
entry:
br label %loop.i.header
@@ -222,7 +222,7 @@ exit:
define void @non_invariant_baseptr_with_identical_underlying_obj2(ptr %A) {
; CHECK-LABEL: 'non_invariant_baseptr_with_identical_underlying_obj2'
; CHECK-NEXT: Src: store i32 1, ptr %idx, align 4 --> Dst: store i32 1, ptr
%idx, align 4
-; CHECK-NEXT: da analyze - none!
+; CHECK-NEXT: da analyze - confused!
;
entry:
br label %loop.i.header
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