670259466b
Currently loop cache analysis uses following formula to evaluate cost of an RefGroup for a consecutive memory access: `RefCost=(TripCount*Stride)/CLS` This cost evaluates to zero when `TripCount*Stride` is smaller than cache-line-size. This results in wrong cost value for a loop and misleads loopInterchange decisions as shown in [this case](https://llvm.godbolt.org/z/jTz1vn4hn). This patch fixes the problem by rounding the cost to 1 once this problem happens.
63 lines
2.4 KiB
LLVM
63 lines
2.4 KiB
LLVM
; RUN: opt < %s -cache-line-size=64 -passes='print<loop-cache-cost>' -disable-output 2>&1 | FileCheck %s
|
|
|
|
;; This test checks the effect of rounding cache cost to 1 when it is
|
|
;; evaluated to 0 because at least 1 cache line is accessed by the loopnest.
|
|
;; It does not make sense to output that zero cache lines are used.
|
|
;; The cost of reference group for B[j], C[j], D[j] and E[j] were
|
|
;; calculted 0 before but now they are 1 which makes each loop cost more reasonable.
|
|
;
|
|
; void test(int n, int m, int o, int A[2][3], int B[2], int C[2], int D[2], int E[2]) {
|
|
; for (int i = 0; i < 3; i++)
|
|
; for (int j = 0; j < 2; j++)
|
|
; A[j][i] = 1;
|
|
; B[j] = 1;
|
|
; C[j] = 1;
|
|
; D[j] = 1
|
|
; E[j] = 1
|
|
; }
|
|
|
|
; CHECK: Loop 'for.j' has cost = 18
|
|
; CHECK-NEXT: Loop 'for.i' has cost = 10
|
|
|
|
define void @test(ptr %A, ptr %B, ptr %C, ptr %D, ptr %E) {
|
|
|
|
entry:
|
|
br label %for.i.preheader.split
|
|
|
|
for.i.preheader.split: ; preds = %for.i.preheader
|
|
br label %for.i
|
|
|
|
for.i: ; preds = %for.inci, %for.i.preheader.split
|
|
%i = phi i64 [ %inci, %for.inci ], [ 0, %for.i.preheader.split ]
|
|
br label %for.j
|
|
|
|
for.j: ; preds = %for.incj, %for.i
|
|
%j = phi i64 [ %incj, %for.j ], [ 0, %for.i ]
|
|
%mul_j = mul nsw i64 %j, 3
|
|
%index_j = add i64 %mul_j, %i
|
|
%arrayidxA = getelementptr inbounds [2 x [ 3 x i32]], ptr %A, i64 %j, i64 %i
|
|
store i32 1, ptr %arrayidxA, align 4
|
|
%arrayidxB = getelementptr inbounds i32, ptr %B, i64 %j
|
|
store i32 1, ptr %arrayidxB, align 4
|
|
%arrayidxC = getelementptr inbounds i32, ptr %C, i64 %j
|
|
store i32 1, ptr %arrayidxC, align 4
|
|
%arrayidxD = getelementptr inbounds i32, ptr %D, i64 %j
|
|
store i32 1, ptr %arrayidxD, align 4
|
|
%arrayidxE = getelementptr inbounds i32, ptr %E, i64 %j
|
|
store i32 1, ptr %arrayidxE, align 4
|
|
%incj = add nsw i64 %j, 1
|
|
%exitcond.us = icmp eq i64 %incj, 2
|
|
br i1 %exitcond.us, label %for.inci, label %for.j
|
|
|
|
for.inci: ; preds = %for.incj
|
|
%inci = add nsw i64 %i, 1
|
|
%exitcond55.us = icmp eq i64 %inci, 3
|
|
br i1 %exitcond55.us, label %for.end.loopexit, label %for.i
|
|
|
|
for.end.loopexit: ; preds = %for.inci
|
|
br label %for.end
|
|
|
|
for.end: ; preds = %for.end.loopexit, %for.cond1.preheader.lr.ph, %entry
|
|
ret void
|
|
}
|