844c188c79
Update getDependenceDistanceStrideAndSize to reason about different combinations of strides directly and explicitly. Update getPtrStride to return 0 for invariant pointers. Then proceed by checking the strides. If either source or sink are not strided by a constant (i.e. not a non-wrapping AddRec) or invariant, the accesses may overlap with earlier or later iterations and we cannot generate runtime checks to disambiguate them. Otherwise they are either loop invariant or strided. In that case, we can generate a runtime check to disambiguate them. If both are strided by constants, we proceed as previously. This is an alternative to https://github.com/llvm/llvm-project/pull/99239 and also replaces additional checks if the underlying object is loop-invariant. Fixes https://github.com/llvm/llvm-project/issues/87189. PR: https://github.com/llvm/llvm-project/pull/99577
70 lines
2.2 KiB
LLVM
70 lines
2.2 KiB
LLVM
; REQUIRES: asserts
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; RUN: opt -passes='print<access-info>' -debug-only=loop-accesses -disable-output < %s 2>&1 | FileCheck %s
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; void negative_step(int *A) {
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; for (int i = 1022; i >= 0; i--)
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; A[i+1] = A[i] + 1;
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; }
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; CHECK-LABEL: 'negative_step'
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; CHECK: LAA: Found an analyzable loop: loop
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; CHECK: LAA: Checking memory dependencies
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; CHECK-NEXT: LAA: Src Scev: {(4092 + %A),+,-4}<nw><%loop>Sink Scev: {(4088 + %A)<nuw>,+,-4}<nw><%loop>
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; CHECK-NEXT: LAA: Distance for store i32 %add, ptr %gep.A.plus.1, align 4 to %l = load i32, ptr %gep.A, align 4: -4
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; CHECK-NEXT: LAA: Src induction step: -1 Sink induction step: -1
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; CHECK-NEXT: LAA: Dependence is negative
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define void @negative_step(ptr nocapture %A) {
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entry:
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%A.plus.1 = getelementptr i32, ptr %A, i64 1
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br label %loop
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loop:
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%iv = phi i64 [ 1022, %entry ], [ %iv.next, %loop ]
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%gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
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%l = load i32, ptr %gep.A, align 4
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%add = add nsw i32 %l, 1
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%gep.A.plus.1 = getelementptr i32, ptr %A.plus.1, i64 %iv
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store i32 %add, ptr %gep.A.plus.1, align 4
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%iv.next = add nsw i64 %iv, -1
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%cmp.not = icmp eq i64 %iv, 0
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br i1 %cmp.not, label %exit, label %loop
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exit:
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ret void
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}
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; void positive_step(int *A) {
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; for (int i = 1; i < 1024; i++)
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; A[i-1] = A[i] + 1;
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; }
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; CHECK-LABEL: 'positive_step'
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; CHECK: LAA: Found an analyzable loop: loop
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; CHECK: LAA: Checking memory dependencies
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; CHECK-NEXT: LAA: Src Scev: {(4 + %A)<nuw>,+,4}<nuw><%loop>Sink Scev: {%A,+,4}<nw><%loop>
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; CHECK-NEXT: LAA: Distance for %l = load i32, ptr %gep.A, align 4 to store i32 %add, ptr %gep.A.minus.1, align 4: -4
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; CHECK-NEXT: LAA: Src induction step: 1 Sink induction step: 1
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; CHECK-NEXT: LAA: Dependence is negative
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define void @positive_step(ptr nocapture %A) {
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entry:
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%A.minus.1 = getelementptr i32, ptr %A, i64 -1
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br label %loop
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loop:
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%iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
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%gep.A = getelementptr inbounds i32, ptr %A, i64 %iv
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%l = load i32, ptr %gep.A, align 4
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%add = add nsw i32 %l, 1
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%gep.A.minus.1 = getelementptr i32, ptr %A.minus.1, i64 %iv
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store i32 %add, ptr %gep.A.minus.1, align 4
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%iv.next = add nsw i64 %iv, 1
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%cmp.not = icmp eq i64 %iv, 1024
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br i1 %cmp.not, label %exit, label %loop
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exit:
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ret void
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}
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