3ad6d1cbe5
As shown in #70473, the following loop was not considered safe to vectorize. When determining the memory access dependencies in a loop which has negative iteration step, we invert the source and sink of the dependence. Perhaps we should just invert the operands to getMinusSCEV(). This way the dependency is not regarded to be true, since the users of the `IsWrite` variables, which correspond to each of the memory accesses, rely on program order and therefore should not be swapped. void vectorizable_Read_Write(int *A) { for (unsigned i = 1022; i >= 0; i--) A[i+1] = A[i] + 1; }
83 lines
2.9 KiB
LLVM
83 lines
2.9 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 4
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; RUN: opt -passes='print<access-info>' -disable-output < %s 2>&1 | FileCheck %s
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target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
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; void vectorizable_Read_Write(int *A) {
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; for (unsigned i = 1022; i >= 0; i--)
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; A[i+1] = A[i] + 1;
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; }
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define void @vectorizable_Read_Write(ptr nocapture %A) {
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; CHECK-LABEL: 'vectorizable_Read_Write'
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; CHECK-NEXT: loop:
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; CHECK-NEXT: Memory dependences are safe
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; CHECK-NEXT: Dependences:
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; CHECK-NEXT: Forward:
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; CHECK-NEXT: %l = load i32, ptr %gep.A, align 4 ->
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; CHECK-NEXT: store i32 %add, ptr %gep.A.plus.1, align 4
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; CHECK-EMPTY:
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; CHECK-NEXT: Run-time memory checks:
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; CHECK-NEXT: Grouped accesses:
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; CHECK-EMPTY:
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; CHECK-NEXT: Non vectorizable stores to invariant address were not found in loop.
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; CHECK-NEXT: SCEV assumptions:
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; CHECK-EMPTY:
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; CHECK-NEXT: Expressions re-written:
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;
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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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define void @neg_step_ForwardButPreventsForwarding(ptr nocapture %A, ptr noalias %B) {
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; CHECK-LABEL: 'neg_step_ForwardButPreventsForwarding'
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; CHECK-NEXT: loop:
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; 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
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; CHECK-NEXT: Forward loop carried data dependence that prevents store-to-load forwarding.
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; CHECK-NEXT: Dependences:
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; CHECK-NEXT: ForwardButPreventsForwarding:
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; CHECK-NEXT: store i32 0, ptr %gep.A, align 4 ->
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; CHECK-NEXT: %l = load i32, ptr %gep.A.plus.1, align 4
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; CHECK-EMPTY:
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; CHECK-NEXT: Run-time memory checks:
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; CHECK-NEXT: Grouped accesses:
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; CHECK-EMPTY:
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; CHECK-NEXT: Non vectorizable stores to invariant address were not found in loop.
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; CHECK-NEXT: SCEV assumptions:
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; CHECK-EMPTY:
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; CHECK-NEXT: Expressions re-written:
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;
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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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store i32 0, ptr %gep.A, align 4
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%gep.A.plus.1 = getelementptr i32, ptr %A.plus.1, i64 %iv
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%l = load i32, ptr %gep.A.plus.1, align 4
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store i32 %l, ptr %B
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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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