forward-loop-independent.ll
2.41 KB
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; RUN: opt -loop-accesses -analyze -enable-new-pm=0 < %s | FileCheck %s
; RUN: opt -passes='require<scalar-evolution>,require<aa>,loop(print-access-info)' -disable-output < %s 2>&1 | FileCheck %s
; Check that loop-indepedent forward dependences are discovered properly.
;
; FIXME: This does not actually always work which is pretty confusing. Right
; now there is hack in LAA that tries to figure out loop-indepedent forward
; dependeces *outside* of the MemoryDepChecker logic (i.e. proper dependence
; analysis).
;
; Therefore if there is only loop-independent dependences for an array
; (i.e. the same index is used), we don't discover the forward dependence.
; So, at ***, we add another non-I-based access of A to trigger
; MemoryDepChecker analysis for accesses of A.
;
; for (unsigned i = 0; i < 100; i++) {
; A[i + 1] = B[i] + 1; // ***
; A[i] = B[i] + 2;
; C[i] = A[i] * 2;
; }
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
define void @f(i32* noalias %A, i32* noalias %B, i32* noalias %C, i64 %N) {
; CHECK: Dependences:
; CHECK-NEXT: Forward:
; CHECK-NEXT: store i32 %b_p1, i32* %Aidx, align 4 ->
; CHECK-NEXT: %a = load i32, i32* %Aidx, align 4
; CHECK: ForwardButPreventsForwarding:
; CHECK-NEXT: store i32 %b_p2, i32* %Aidx_next, align 4 ->
; CHECK-NEXT: %a = load i32, i32* %Aidx, align 4
; CHECK: Forward:
; CHECK-NEXT: store i32 %b_p2, i32* %Aidx_next, align 4 ->
; CHECK-NEXT: store i32 %b_p1, i32* %Aidx, align 4
entry:
br label %for.body
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%Bidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv
%Cidx = getelementptr inbounds i32, i32* %C, i64 %indvars.iv
%Aidx_next = getelementptr inbounds i32, i32* %A, i64 %indvars.iv.next
%Aidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
%b = load i32, i32* %Bidx, align 4
%b_p2 = add i32 %b, 1
store i32 %b_p2, i32* %Aidx_next, align 4
%b_p1 = add i32 %b, 2
store i32 %b_p1, i32* %Aidx, align 4
%a = load i32, i32* %Aidx, align 4
%c = mul i32 %a, 2
store i32 %c, i32* %Cidx, align 4
%exitcond = icmp eq i64 %indvars.iv.next, %N
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
ret void
}