1; RUN: opt -passes=loop-load-elim -S < %s | FileCheck %s 2 3; Simple st->ld forwarding derived from a lexical backward dep. 4; 5; for (unsigned i = 0; i < 100; i++) 6; A[i+1] = A[i] + B[i]; 7 8target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" 9 10define void @f(ptr noalias nocapture %A, ptr noalias nocapture readonly %B, i64 %N) { 11entry: 12; CHECK: %load_initial = load i32, ptr %A 13 br label %for.body 14 15for.body: ; preds = %for.body, %entry 16; CHECK: %store_forwarded = phi i32 [ %load_initial, %entry ], [ %add, %for.body ] 17 %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ] 18 %arrayidx = getelementptr inbounds i32, ptr %A, i64 %indvars.iv 19 %load = load i32, ptr %arrayidx, align 4 20 %arrayidx2 = getelementptr inbounds i32, ptr %B, i64 %indvars.iv 21 %load_1 = load i32, ptr %arrayidx2, align 4 22; CHECK: %add = add i32 %load_1, %store_forwarded 23 %add = add i32 %load_1, %load 24 %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1 25 %arrayidx_next = getelementptr inbounds i32, ptr %A, i64 %indvars.iv.next 26 store i32 %add, ptr %arrayidx_next, align 4 27 %exitcond = icmp eq i64 %indvars.iv.next, %N 28 br i1 %exitcond, label %for.end, label %for.body 29 30for.end: ; preds = %for.body 31 ret void 32} 33 34; Same but loop is descending. 35; 36; for (unsigned i = N; i > 0; i--) 37; A[i-1] = A[i] + B[i]; 38define void @g(ptr noalias nocapture %A, ptr noalias nocapture readonly %B, i64 %N) { 39entry: 40; CHECK: %0 = shl i64 %N, 2 41; CHECK: %scevgep = getelementptr i8, ptr %A, i64 %0 42; CHECK: %load_initial = load i32, ptr %scevgep, align 4 43 br label %for.body 44 45for.body: ; preds = %for.body, %entry 46; CHECK: %store_forwarded = phi i32 [ %load_initial, %entry ], [ %add, %for.body ] 47 %i.09 = phi i64 [ %sub, %for.body ], [ %N, %entry ] 48 %arrayidx = getelementptr inbounds i32, ptr %A, i64 %i.09 49 %load = load i32, ptr %arrayidx, align 4 50 %arrayidx1 = getelementptr inbounds i32, ptr %B, i64 %i.09 51 %load_1 = load i32, ptr %arrayidx1, align 4 52; CHECK: %add = add i32 %load_1, %store_forwarded 53 %add = add i32 %load_1, %load 54 %sub = add i64 %i.09, -1 55 %arrayidx2 = getelementptr inbounds i32, ptr %A, i64 %sub 56 store i32 %add, ptr %arrayidx2, align 4 57 %cmp.not = icmp eq i64 %sub, 0 58 br i1 %cmp.not, label %for.end, label %for.body 59 60for.end: ; preds = %for.body 61 ret void 62} 63 64