93832466cc
Fix GitHub issue #149991 where Strong SIV test incorrectly concludes 'none!' for symbolic coefficients that could be zero, leading to 0/0 undef behavior. The Strong SIV test was incorrectly concluding "no dependence" when the coefficient is symbolic and the delta (difference between source and destination) is zero. When delta=0, the Strong SIV test divides delta/coeff to get the distance. The bug occurs when coeff is an unknown symbolic value: if coeff=0 at runtime, then 0/0 is undefined and all iterations access the same memory location, creating a true dependence that was being missed.
35 lines
1.3 KiB
LLVM
35 lines
1.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -disable-output "-passes=print<da>" -aa-pipeline=basic-aa 2>&1 \
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; RUN: | FileCheck %s
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; Test case for bug #149991 where Strong SIV test incorrectly concludes "no dependence"
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; when the coefficient is symbolic (unknown at compile time) and delta is zero.
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;
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; In this case, the array access is A[k*i] with both src and dst at the same
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; location in the same iteration. If k=0, then all iterations access the same
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; element, meaning there IS a dependence between different iterations.
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; The Strong SIV test should add a runtime assumption that k != 0.
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define void @test_zero_coefficient(ptr noalias %A, i64 %k) {
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; CHECK-LABEL: 'test_zero_coefficient'
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; CHECK-NEXT: Src: store i8 42, ptr %idx, align 1 --> Dst: store i8 42, ptr %idx, align 1
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; CHECK-NEXT: da analyze - consistent output [0]!
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; CHECK-NEXT: Runtime Assumptions:
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; CHECK-NEXT: Compare predicate: %k ne) 0
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;
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entry:
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br label %loop
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loop:
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%i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
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%off = mul nsw i64 %i, %k
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%idx = getelementptr inbounds i8, ptr %A, i64 %off
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store i8 42, ptr %idx, align 1
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%i.next = add nsw i64 %i, 1
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%cmp = icmp slt i64 %i.next, 100
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br i1 %cmp, label %loop, label %exit
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exit:
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ret void
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}
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