release/18.x: [ValueTracking] Treat phi as underlying obj when not decomposing further (#84339) #84950
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@nikic What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-llvm-analysis Author: None (llvmbot) ChangesRequested by: @nikic Full diff: https://github.com/llvm/llvm-project/pull/84950.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 412115eb649c2f..9f9451e4e814ac 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5986,6 +5986,8 @@ void llvm::getUnderlyingObjects(const Value *V,
if (!LI || !LI->isLoopHeader(PN->getParent()) ||
isSameUnderlyingObjectInLoop(PN, LI))
append_range(Worklist, PN->incoming_values());
+ else
+ Objects.push_back(P);
continue;
}
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-loop-varying-phi.ll b/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-loop-varying-phi.ll
new file mode 100644
index 00000000000000..106dc8c13a49fa
--- /dev/null
+++ b/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-loop-varying-phi.ll
@@ -0,0 +1,180 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -passes='print<access-info>' -disable-output %s 2>&1 | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+
+; Test case for https://github.com/llvm/llvm-project/issues/82665.
+define void @indirect_ptr_recurrences_read_write(ptr %A, ptr %B) {
+; CHECK-LABEL: 'indirect_ptr_recurrences_read_write'
+; 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: Unsafe indirect dependence.
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: IndidrectUnsafe:
+; CHECK-NEXT: %l = load i32, ptr %ptr.recur, align 4, !tbaa !4 ->
+; CHECK-NEXT: store i32 %xor, ptr %ptr.recur, align 4, !tbaa !4
+; 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:
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
+ %ptr.recur = phi ptr [ %A, %entry ], [ %ptr.next, %loop ]
+ %gep.B = getelementptr inbounds ptr, ptr %B, i64 %iv
+ %ptr.next = load ptr, ptr %gep.B, align 8, !tbaa !6
+ %l = load i32, ptr %ptr.recur, align 4, !tbaa !10
+ %xor = xor i32 %l, 1
+ store i32 %xor, ptr %ptr.recur, align 4, !tbaa !10
+ %iv.next = add nuw nsw i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, 5
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ ret void
+}
+
+define i32 @indirect_ptr_recurrences_read_only_loop(ptr %A, ptr %B) {
+; CHECK-LABEL: 'indirect_ptr_recurrences_read_only_loop'
+; 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:
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
+ %ptr.recur = phi ptr [ %A, %entry ], [ %ptr.next, %loop ]
+ %red = phi i32 [ 0, %entry ], [ %xor, %loop ]
+ %gep.B = getelementptr inbounds ptr, ptr %B, i64 %iv
+ %ptr.next = load ptr, ptr %gep.B, align 8, !tbaa !6
+ %l = load i32, ptr %ptr.recur, align 4, !tbaa !10
+ %xor = xor i32 %l, 1
+ %iv.next = add nuw nsw i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, 5
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ ret i32 %xor
+}
+
+define void @indirect_ptr_recurrences_read_write_may_alias_no_tbaa(ptr %A, ptr %B) {
+; CHECK-LABEL: 'indirect_ptr_recurrences_read_write_may_alias_no_tbaa'
+; CHECK-NEXT: loop:
+; CHECK-NEXT: Report: cannot identify array bounds
+; 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:
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
+ %ptr.recur = phi ptr [ %A, %entry ], [ %ptr.next, %loop ]
+ %gep.B = getelementptr inbounds ptr, ptr %B, i64 %iv
+ %ptr.next = load ptr, ptr %gep.B, align 8, !tbaa !6
+ %l = load i32, ptr %ptr.recur, align 4
+ %xor = xor i32 %l, 1
+ store i32 %xor, ptr %ptr.recur, align 4
+ %iv.next = add nuw nsw i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, 5
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ ret void
+}
+
+define void @indirect_ptr_recurrences_read_write_may_alias_different_obj(ptr %A, ptr %B, ptr %C) {
+; CHECK-LABEL: 'indirect_ptr_recurrences_read_write_may_alias_different_obj'
+; CHECK-NEXT: loop:
+; CHECK-NEXT: Report: cannot identify array bounds
+; 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:
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
+ %ptr.recur = phi ptr [ %A, %entry ], [ %ptr.next, %loop ]
+ %gep.B = getelementptr inbounds ptr, ptr %B, i64 %iv
+ %ptr.next = load ptr, ptr %gep.B, align 8, !tbaa !6
+ %l = load i32, ptr %ptr.recur, align 4
+ %xor = xor i32 %l, 1
+ %gep.C = getelementptr inbounds ptr, ptr %C, i64 %iv
+ store i32 %xor, ptr %gep.C, align 4
+ %iv.next = add nuw nsw i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, 5
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ ret void
+}
+
+define void @indirect_ptr_recurrences_read_write_may_noalias_different_obj(ptr %A, ptr %B, ptr noalias %C) {
+; CHECK-LABEL: 'indirect_ptr_recurrences_read_write_may_noalias_different_obj'
+; 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:
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
+ %ptr.recur = phi ptr [ %A, %entry ], [ %ptr.next, %loop ]
+ %gep.B = getelementptr inbounds ptr, ptr %B, i64 %iv
+ %ptr.next = load ptr, ptr %gep.B, align 8, !tbaa !6
+ %l = load i32, ptr %ptr.recur, align 4
+ %xor = xor i32 %l, 1
+ %gep.C = getelementptr inbounds ptr, ptr %C, i64 %iv
+ store i32 %xor, ptr %gep.C, align 4
+ %iv.next = add nuw nsw i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, 5
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ ret void
+}
+
+
+!6 = !{!7, !7, i64 0}
+!7 = !{!"any pointer", !8, i64 0}
+!8 = !{!"omnipotent char", !9, i64 0}
+!9 = !{!"Simple C/C++ TBAA"}
+!10 = !{!11, !11, i64 0}
+!11 = !{!"int", !8, i64 0}
|
Test case for llvm#82665. (cherry picked from commit 4cfd4a7)
…her (llvm#84339) At the moment, getUnderlyingObjects simply continues for phis that do not refer to the same underlying object in loops, without adding them to the list of underlying objects, effectively ignoring those phis. Instead of ignoring those phis, add them to the list of underlying objects. This fixes a miscompile where LoopAccessAnalysis fails to identify a memory dependence, because no underlying objects can be found for a set of memory accesses. Fixes llvm#82665. PR: llvm#84339 (cherry picked from commit b274b23)
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Backport 4cfd4a7 b274b23
Requested by: @nikic