[llvm] LAA: add missed swap when inverting src, sink (PR #122254)
Ramkumar Ramachandra via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 13 03:13:33 PST 2025
https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/122254
>From 820111fa23d28c4b2e39ad14eec4196a6a154a14 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 9 Jan 2025 13:40:08 +0000
Subject: [PATCH 1/2] LAA: add pre-commit test for missed swap
---
.../LoopAccessAnalysis/depend_diff_types.ll | 81 +++++++++++++++++++
1 file changed, 81 insertions(+)
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll b/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
index 0bdcc357901487..df42f61306a5de 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
@@ -194,3 +194,84 @@ loop:
exit:
ret void
}
+
+; In the following test, the sink is loop-invariant.
+
+define void @type_size_equivalence_sink_loopinv(ptr nocapture %vec, i64 %n) {
+; CHECK-LABEL: 'type_size_equivalence_sink_loopinv'
+; CHECK-NEXT: loop:
+; CHECK-NEXT: Memory dependences are safe
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: Run-time memory checks:
+; CHECK-NEXT: Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT: Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT: SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT: Expressions re-written:
+;
+entry:
+ %gep.n = getelementptr inbounds i64, ptr %vec, i64 %n
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+
+ %gep.iv = getelementptr i64, ptr %vec, i64 %iv
+ %ld.i64 = load i64, ptr %gep.iv, align 8
+
+ %ld.i64.i32 = trunc i64 %ld.i64 to i32
+ store i32 %ld.i64.i32, ptr %gep.n, align 8
+
+ %iv.next = add nuw nsw i64 %iv, 1
+ %cond = icmp eq i64 %iv.next, %n
+ br i1 %cond, label %exit, label %loop
+
+exit:
+ ret void
+}
+
+; Variant of the above, with a negative induction step and a gep exposing
+; type-mismtach.
+
+define void @type_size_equivalence_sink_loopinv_negind(ptr nocapture %vec, i64 %n) {
+; CHECK-LABEL: 'type_size_equivalence_sink_loopinv_negind'
+; CHECK-NEXT: loop:
+; CHECK-NEXT: Report: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
+; CHECK-NEXT: Unknown data dependence.
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: Unknown:
+; CHECK-NEXT: %ld.i64 = load i64, ptr %gep.minus.iv.4, align 8 ->
+; CHECK-NEXT: store i32 %ld.i64.i32, ptr %gep.minus.n, align 8
+; CHECK-EMPTY:
+; CHECK-NEXT: Run-time memory checks:
+; CHECK-NEXT: Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT: Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT: SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT: Expressions re-written:
+;
+entry:
+ %minus.n = sub nsw i64 0, %n
+ %gep.minus.n = getelementptr inbounds i64, ptr %vec, i64 %minus.n
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+
+ %minus.iv = sub nsw i64 0, %iv
+ %gep.minus.iv = getelementptr i64, ptr %vec, i64 %minus.iv
+ %gep.minus.iv.4 = getelementptr i8, ptr %gep.minus.iv, i64 -4
+ %ld.i64 = load i64, ptr %gep.minus.iv.4, align 8
+
+ %ld.i64.i32 = trunc i64 %ld.i64 to i32
+ store i32 %ld.i64.i32, ptr %gep.minus.n, align 8
+
+ %iv.next = add nuw nsw i64 %iv, 1
+ %cond = icmp eq i64 %iv.next, %n
+ br i1 %cond, label %exit, label %loop
+
+exit:
+ ret void
+}
>From ed5b69e2bdd7f9f7ad776ed03f34378a3d0ccfa2 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 9 Jan 2025 11:13:45 +0000
Subject: [PATCH 2/2] LAA: add missed swap when inverting src, sink
When inverting source and sink on a negative induction step, the types
of the source and sink should also be swapped. This fixes a bug in the
code that follows, that computes properties based on these types. With
234cc40 ([LAA] Limit no-overlap check to at least one loop-invariant
accesses.), that code is guarded by a loop-invariant condition: however,
the commit did not add any new tests exercising the guarded code, and
hence the bugfix in this patch requires additional tests to exercise
that guarded codepath.
---
llvm/lib/Analysis/LoopAccessAnalysis.cpp | 1 +
llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll | 7 +------
2 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 38e9145826c08e..2a68979add666d 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1921,6 +1921,7 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
if (StrideAPtr && *StrideAPtr < 0) {
std::swap(Src, Sink);
std::swap(AInst, BInst);
+ std::swap(ATy, BTy);
std::swap(StrideAPtr, StrideBPtr);
}
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll b/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
index df42f61306a5de..e855578e794fa9 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
@@ -237,13 +237,8 @@ exit:
define void @type_size_equivalence_sink_loopinv_negind(ptr nocapture %vec, i64 %n) {
; CHECK-LABEL: 'type_size_equivalence_sink_loopinv_negind'
; CHECK-NEXT: loop:
-; CHECK-NEXT: Report: unsafe dependent memory operations in loop. Use #pragma clang loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
-; CHECK-NEXT: Unknown data dependence.
+; CHECK-NEXT: Memory dependences are safe
; CHECK-NEXT: Dependences:
-; CHECK-NEXT: Unknown:
-; CHECK-NEXT: %ld.i64 = load i64, ptr %gep.minus.iv.4, align 8 ->
-; CHECK-NEXT: store i32 %ld.i64.i32, ptr %gep.minus.n, align 8
-; CHECK-EMPTY:
; CHECK-NEXT: Run-time memory checks:
; CHECK-NEXT: Grouped accesses:
; CHECK-EMPTY:
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