778b455dd6
Adds new optimization remarks when vectorization fails. More specifically, new remarks are added for following 4 cases: - Backward dependency - Backward dependency that prevents Store-to-load forwarding - Forward dependency that prevents Store-to-load forwarding - Unknown dependency It is important to note that only one of the sources of failures (to vectorize) is reported by the remarks. This source of failure may not be first in program order. A regression test has been added to test the following cases: a) Loop can be vectorized: No optimization remark is emitted b) Loop can not be vectorized: In this case an optimization remark will be emitted for one source of failure. Reviewed By: sdesmalen, david-arm Differential Revision: https://reviews.llvm.org/D108371
154 lines
4.7 KiB
LLVM
154 lines
4.7 KiB
LLVM
; RUN: opt -passes='require<scalar-evolution>,require<aa>,loop(print-access-info)' -disable-output < %s 2>&1 | FileCheck %s
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; This loop:
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;
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; int **A;
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; for (i)
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; for (j) {
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; A[i][j] = A[i-1][j] * B[j]
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; B[j+1] = 2 // backward dep between this and the previous
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; }
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;
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; is transformed by Load-PRE to stash away A[i] for the next iteration of the
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; outer loop:
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;
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; Curr = A[0]; // Prev_0
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; for (i: 1..N) {
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; Prev = Curr; // Prev = PHI (Prev_0, Curr)
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; Curr = A[i];
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; for (j: 0..N) {
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; Curr[j] = Prev[j] * B[j]
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; B[j+1] = 2 // backward dep between this and the previous
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; }
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; }
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;
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; Since A[i] and A[i-1] are likely to be independent, getUnderlyingObjects
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; should not assume that Curr and Prev share the same underlying object.
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;
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; If it did we would try to dependence-analyze Curr and Prev and the analysis
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; would fail with non-constant distance.
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;
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; To illustrate one of the negative consequences of this, if the loop has a
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; backward dependence we won't detect this but instead fully fall back on
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; memchecks (that is what LAA does after encountering a case of non-constant
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; distance).
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.10.0"
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; CHECK-LABEL: function 'f'
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; CHECK: for_j.body:
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; CHECK-NEXT: Report: unsafe dependent memory operations in loop
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; CHECK-NEXT: Backward loop carried data dependence.
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; CHECK-NEXT: Dependences:
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; CHECK-NEXT: Backward:
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; CHECK-NEXT: %loadB = load i8, i8* %gepB, align 1 ->
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; CHECK-NEXT: store i8 2, i8* %gepB_plus_one, align 1
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define void @f(i8** noalias %A, i8* noalias %B, i64 %N) {
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for_i.preheader:
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%prev_0 = load i8*, i8** %A, align 8
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br label %for_i.body
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for_i.body:
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%i = phi i64 [1, %for_i.preheader], [%i.1, %for_j.end]
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%prev = phi i8* [%prev_0, %for_i.preheader], [%curr, %for_j.end]
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%gep = getelementptr inbounds i8*, i8** %A, i64 %i
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%curr = load i8*, i8** %gep, align 8
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br label %for_j.preheader
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for_j.preheader:
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br label %for_j.body
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for_j.body:
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%j = phi i64 [0, %for_j.preheader], [%j.1, %for_j.body]
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%gepPrev = getelementptr inbounds i8, i8* %prev, i64 %j
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%gepCurr = getelementptr inbounds i8, i8* %curr, i64 %j
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%gepB = getelementptr inbounds i8, i8* %B, i64 %j
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%loadPrev = load i8, i8* %gepPrev, align 1
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%loadB = load i8, i8* %gepB, align 1
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%mul = mul i8 %loadPrev, %loadB
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store i8 %mul, i8* %gepCurr, align 1
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%gepB_plus_one = getelementptr inbounds i8, i8* %gepB, i64 1
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store i8 2, i8* %gepB_plus_one, align 1
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%j.1 = add nuw i64 %j, 1
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%exitcondj = icmp eq i64 %j.1, %N
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br i1 %exitcondj, label %for_j.end, label %for_j.body
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for_j.end:
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%i.1 = add nuw i64 %i, 1
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%exitcond = icmp eq i64 %i.1, %N
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br i1 %exitcond, label %for_i.end, label %for_i.body
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for_i.end:
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ret void
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}
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; CHECK-LABEL: function 'f_deep'
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; CHECK: for_j.body:
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; FIXME: This is incorrect and is going to be fixed with D86669.
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; CHECK-NEXT: Memory dependences are safe with run-time checks
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; CHECK-NEXT: Dependences:
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define void @f_deep(i8** noalias %A, i8* noalias %B, i64 %N) {
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for_i.preheader:
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%prev_0 = load i8*, i8** %A, align 8
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br label %for_i.body
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for_i.body:
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%i = phi i64 [1, %for_i.preheader], [%i.1, %for_j.end]
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%prev = phi i8* [%prev_0, %for_i.preheader], [%curr, %for_j.end]
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%gep = getelementptr inbounds i8*, i8** %A, i64 %i
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%curr = load i8*, i8** %gep, align 8
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br label %for_j.preheader
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for_j.preheader:
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br label %for_j.body
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for_j.body:
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%j = phi i64 [0, %for_j.preheader], [%j.1, %for_j.body]
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%gepPrev = getelementptr inbounds i8, i8* %prev, i64 %j
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%gepCurr = getelementptr inbounds i8, i8* %curr, i64 %j
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%gepB = getelementptr inbounds i8, i8* %B, i64 %j
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%gepB1 = getelementptr inbounds i8, i8* %gepB, i64 %j
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%gepB2 = getelementptr inbounds i8, i8* %gepB1, i64 0
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%gepB3 = getelementptr inbounds i8, i8* %gepB2, i64 0
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%gepB4 = getelementptr inbounds i8, i8* %gepB3, i64 0
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%gepB5 = getelementptr inbounds i8, i8* %gepB4, i64 0
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%gepB6 = getelementptr inbounds i8, i8* %gepB5, i64 0
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%gepB7 = getelementptr inbounds i8, i8* %gepB6, i64 0
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%gepB8 = getelementptr inbounds i8, i8* %gepB7, i64 0
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%gepB9 = getelementptr inbounds i8, i8* %gepB8, i64 0
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%loadPrev = load i8, i8* %gepPrev, align 1
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%loadB = load i8, i8* %gepB9, align 1
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%mul = mul i8 %loadPrev, %loadB
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store i8 %mul, i8* %gepCurr, align 1
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%gepB_plus_one = getelementptr inbounds i8, i8* %gepB, i64 1
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store i8 2, i8* %gepB_plus_one, align 1
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%j.1 = add nuw i64 %j, 1
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%exitcondj = icmp eq i64 %j.1, %N
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br i1 %exitcondj, label %for_j.end, label %for_j.body
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for_j.end:
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%i.1 = add nuw i64 %i, 1
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%exitcond = icmp eq i64 %i.1, %N
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br i1 %exitcond, label %for_i.end, label %for_i.body
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for_i.end:
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ret void
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}
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