forked from OSchip/llvm-project
91 lines
2.6 KiB
LLVM
91 lines
2.6 KiB
LLVM
; RUN: opt -basicaa -loop-accesses -analyze < %s | FileCheck %s
|
|
|
|
; This loop:
|
|
;
|
|
; int **A;
|
|
; for (i)
|
|
; for (j) {
|
|
; A[i][j] = A[i-1][j] * B[j]
|
|
; B[j+1] = 2 // backward dep between this and the previous
|
|
; }
|
|
;
|
|
; is transformed by Load-PRE to stash away A[i] for the next iteration of the
|
|
; outer loop:
|
|
;
|
|
; Curr = A[0]; // Prev_0
|
|
; for (i: 1..N) {
|
|
; Prev = Curr; // Prev = PHI (Prev_0, Curr)
|
|
; Curr = A[i];
|
|
; for (j: 0..N) {
|
|
; Curr[j] = Prev[j] * B[j]
|
|
; B[j+1] = 2 // backward dep between this and the previous
|
|
; }
|
|
; }
|
|
;
|
|
; Since A[i] and A[i-1] are likely to be independent, getUnderlyingObjects
|
|
; should not assume that Curr and Prev share the same underlying object.
|
|
;
|
|
; If it did we would try to dependence-analyze Curr and Prev and the analysis
|
|
; would fail with non-constant distance.
|
|
;
|
|
; To illustrate one of the negative consequences of this, if the loop has a
|
|
; backward dependence we won't detect this but instead fully fall back on
|
|
; memchecks (that is what LAA does after encountering a case of non-constant
|
|
; distance).
|
|
|
|
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
|
|
target triple = "x86_64-apple-macosx10.10.0"
|
|
|
|
; CHECK: for_j.body:
|
|
; CHECK-NEXT: Report: unsafe dependent memory operations in loop
|
|
; CHECK-NEXT: Dependences:
|
|
; CHECK-NEXT: Backward:
|
|
; CHECK-NEXT: %loadB = load i8, i8* %gepB, align 1 ->
|
|
; CHECK-NEXT: store i8 2, i8* %gepB_plus_one, align 1
|
|
|
|
define void @f(i8** noalias %A, i8* noalias %B, i64 %N) {
|
|
for_i.preheader:
|
|
%prev_0 = load i8*, i8** %A, align 8
|
|
br label %for_i.body
|
|
|
|
for_i.body:
|
|
%i = phi i64 [1, %for_i.preheader], [%i.1, %for_j.end]
|
|
%prev = phi i8* [%prev_0, %for_i.preheader], [%curr, %for_j.end]
|
|
%gep = getelementptr inbounds i8*, i8** %A, i64 %i
|
|
%curr = load i8*, i8** %gep, align 8
|
|
br label %for_j.preheader
|
|
|
|
for_j.preheader:
|
|
br label %for_j.body
|
|
|
|
for_j.body:
|
|
%j = phi i64 [0, %for_j.preheader], [%j.1, %for_j.body]
|
|
|
|
%gepPrev = getelementptr inbounds i8, i8* %prev, i64 %j
|
|
%gepCurr = getelementptr inbounds i8, i8* %curr, i64 %j
|
|
%gepB = getelementptr inbounds i8, i8* %B, i64 %j
|
|
|
|
%loadPrev = load i8, i8* %gepPrev, align 1
|
|
%loadB = load i8, i8* %gepB, align 1
|
|
|
|
%mul = mul i8 %loadPrev, %loadB
|
|
|
|
store i8 %mul, i8* %gepCurr, align 1
|
|
|
|
%gepB_plus_one = getelementptr inbounds i8, i8* %gepB, i64 1
|
|
store i8 2, i8* %gepB_plus_one, align 1
|
|
|
|
%j.1 = add nuw i64 %j, 1
|
|
%exitcondj = icmp eq i64 %j.1, %N
|
|
br i1 %exitcondj, label %for_j.end, label %for_j.body
|
|
|
|
for_j.end:
|
|
|
|
%i.1 = add nuw i64 %i, 1
|
|
%exitcond = icmp eq i64 %i.1, %N
|
|
br i1 %exitcond, label %for_i.end, label %for_i.body
|
|
|
|
for_i.end:
|
|
ret void
|
|
}
|