[llvm] 9d42c75 - [LAA] Fix picking context instr in evaluatePtrAddRec for multiple preds.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 30 12:11:45 PDT 2025
Author: Florian Hahn
Date: 2025-09-30T20:04:29+01:00
New Revision: 9d42c752569f3141ca42b75dd37f45e771ffa7a0
URL: https://github.com/llvm/llvm-project/commit/9d42c752569f3141ca42b75dd37f45e771ffa7a0
DIFF: https://github.com/llvm/llvm-project/commit/9d42c752569f3141ca42b75dd37f45e771ffa7a0.diff
LOG: [LAA] Fix picking context instr in evaluatePtrAddRec for multiple preds.
A loop may have more than one predecessor out of the loop. In that case,
just pick the first non-phi instruction in the loop header.
Added:
Modified:
llvm/lib/Analysis/LoopAccessAnalysis.cpp
llvm/test/Analysis/LoopAccessAnalysis/early-exit-runtime-checks.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 05f7ac694ac9b..47dccde45337b 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -234,9 +234,14 @@ static bool evaluatePtrAddRecAtMaxBTCWillNotWrap(
// Check if we have a suitable dereferencable assumption we can use.
if (!StartPtrV->canBeFreed()) {
+ Instruction *CtxI = &*L->getHeader()->getFirstNonPHIIt();
+ if (BasicBlock *LoopPred = L->getLoopPredecessor()) {
+ if (isa<BranchInst>(LoopPred->getTerminator()))
+ CtxI = LoopPred->getTerminator();
+ }
+
RetainedKnowledge DerefRK = getKnowledgeValidInContext(
- StartPtrV, {Attribute::Dereferenceable}, *AC,
- L->getLoopPredecessor()->getTerminator(), DT);
+ StartPtrV, {Attribute::Dereferenceable}, *AC, CtxI, DT);
if (DerefRK) {
DerefBytesSCEV =
SE.getUMaxExpr(DerefBytesSCEV, SE.getSCEV(DerefRK.IRArgValue));
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/early-exit-runtime-checks.ll b/llvm/test/Analysis/LoopAccessAnalysis/early-exit-runtime-checks.ll
index 207a44d5d08d4..a08f859858d24 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/early-exit-runtime-checks.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/early-exit-runtime-checks.ll
@@ -565,6 +565,138 @@ e.2:
ret void
}
+define void @all_exits_dominate_latch_countable_exits_at_most_500_iterations_known_deref_via_assumption_multiple_predecessors(ptr %A, ptr %B, i1 %c) nosync nofree {
+; CHECK-LABEL: 'all_exits_dominate_latch_countable_exits_at_most_500_iterations_known_deref_via_assumption_multiple_predecessors'
+; CHECK-NEXT: loop.header:
+; CHECK-NEXT: Memory dependences are safe with run-time checks
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: Run-time memory checks:
+; CHECK-NEXT: Check 0:
+; CHECK-NEXT: Comparing group GRP0:
+; CHECK-NEXT: %gep.B = getelementptr inbounds i32, ptr %B, i64 %iv
+; CHECK-NEXT: Against group GRP1:
+; CHECK-NEXT: %gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
+; CHECK-NEXT: Grouped accesses:
+; CHECK-NEXT: Group GRP0:
+; CHECK-NEXT: (Low: %B High: (2000 + %B))
+; CHECK-NEXT: Member: {%B,+,4}<nuw><%loop.header>
+; CHECK-NEXT: Group GRP1:
+; CHECK-NEXT: (Low: %A High: (2000 + %A))
+; CHECK-NEXT: Member: {%A,+,4}<nuw><%loop.header>
+; 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:
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %A, i64 2000) ]
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %B, i64 2000) ]
+ br i1 %c, label %then, label %else
+
+then:
+ br label %loop.header
+
+else:
+ br label %loop.header
+
+loop.header:
+ %iv = phi i64 [ 0, %then ], [ 0, %else ], [ %iv.next, %latch ]
+ %gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
+ %gep.B = getelementptr inbounds i32, ptr %B, i64 %iv
+ %l = load i32, ptr %gep.A, align 4
+ store i32 0, ptr %gep.B, align 4
+ %cntable.c.1 = icmp ult i64 %iv, 1000
+ %iv.next = add nuw nsw i64 %iv, 1
+ br i1 %cntable.c.1, label %b2, label %e.1
+
+b2:
+ %uncntable.c.0 = icmp eq i32 %l, 0
+ br i1 %uncntable.c.0, label %e.2, label %b3
+
+b3:
+ %cntable.c.2 = icmp eq i64 %iv.next, 500
+ br i1 %cntable.c.2, label %cleanup4, label %latch
+
+latch:
+ br label %loop.header
+
+cleanup4:
+ ret void
+
+e.1:
+ ret void
+
+e.2:
+ ret void
+}
+
+define void @all_exits_dominate_latch_countable_exits_at_most_500_iterations_known_deref_via_assumption_multiple_predecessors_no_valid(ptr %A, ptr %B, i1 %c) nosync nofree {
+; CHECK-LABEL: 'all_exits_dominate_latch_countable_exits_at_most_500_iterations_known_deref_via_assumption_multiple_predecessors_no_valid'
+; CHECK-NEXT: loop.header:
+; CHECK-NEXT: Memory dependences are safe with run-time checks
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: Run-time memory checks:
+; CHECK-NEXT: Check 0:
+; CHECK-NEXT: Comparing group GRP0:
+; CHECK-NEXT: %gep.B = getelementptr inbounds i32, ptr %B, i64 %iv
+; CHECK-NEXT: Against group GRP1:
+; CHECK-NEXT: %gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
+; CHECK-NEXT: Grouped accesses:
+; CHECK-NEXT: Group GRP0:
+; CHECK-NEXT: (Low: %B High: inttoptr (i64 -1 to ptr))
+; CHECK-NEXT: Member: {%B,+,4}<nuw><%loop.header>
+; CHECK-NEXT: Group GRP1:
+; CHECK-NEXT: (Low: %A High: (2000 + %A))
+; CHECK-NEXT: Member: {%A,+,4}<nuw><%loop.header>
+; 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:
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %A, i64 2000) ]
+ br i1 %c, label %then, label %else
+
+then:
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %B, i64 2000) ]
+ br label %loop.header
+
+else:
+ br label %loop.header
+
+loop.header:
+ %iv = phi i64 [ 0, %then ], [ 0, %else ], [ %iv.next, %latch ]
+ %gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
+ %gep.B = getelementptr inbounds i32, ptr %B, i64 %iv
+ %l = load i32, ptr %gep.A, align 4
+ store i32 0, ptr %gep.B, align 4
+ %cntable.c.1 = icmp ult i64 %iv, 1000
+ %iv.next = add nuw nsw i64 %iv, 1
+ br i1 %cntable.c.1, label %b2, label %e.1
+
+b2:
+ %uncntable.c.0 = icmp eq i32 %l, 0
+ br i1 %uncntable.c.0, label %e.2, label %b3
+
+b3:
+ %cntable.c.2 = icmp eq i64 %iv.next, 500
+ br i1 %cntable.c.2, label %cleanup4, label %latch
+
+latch:
+ br label %loop.header
+
+cleanup4:
+ ret void
+
+e.1:
+ ret void
+
+e.2:
+ ret void
+}
+
define void @all_exits_dominate_latch_countable_exits_at_most_500_iterations_deref_via_assumption_too_small(ptr %A, ptr %B) nosync nofree {
; CHECK-LABEL: 'all_exits_dominate_latch_countable_exits_at_most_500_iterations_deref_via_assumption_too_small'
; CHECK-NEXT: loop.header:
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