1 ; RUN: opt < %s -loop-unroll -indvars -disable-output 2 3 @b = external global i32, align 4 4 5 ; Test that LoopUnroll does not break LCSSA form. 6 ; 7 ; In this function we have a following CFG: 8 ; ( entry ) 9 ; | 10 ; v 11 ; ( outer.header ) <-- 12 ; | \ 13 ; v | 14 ; --> ( inner.header ) | 15 ; / / \ | 16 ; \ / \ | 17 ; \ v v / 18 ; ( inner.latch ) ( outer.latch ) 19 ; | 20 ; v 21 ; ( exit ) 22 ; 23 ; When the inner loop is unrolled, we inner.latch block has only one 24 ; predecessor and one successor, so it can be merged with exit block. 25 ; During the merge, however, we remove an LCSSA definition for 26 ; %storemerge1.lcssa, breaking LCSSA form for the outer loop. 27 28 ; Function Attrs: nounwind uwtable 29 define void @fn1() #0 { 30 entry: 31 br label %outer.header 32 33 outer.header: ; preds = %outer.latch, %entry 34 %storemerge1 = phi i32 [ 0, %entry ], [ %inc9, %outer.latch ] 35 br label %inner.header 36 37 inner.header: ; preds = %inner.latch, %outer.header 38 %storemerge = phi i32 [ %add, %inner.latch ], [ 0, %outer.header ] 39 %cmp = icmp slt i32 %storemerge, 1 40 br i1 %cmp, label %inner.latch, label %outer.latch 41 42 inner.latch: ; preds = %inner.header 43 %tobool4 = icmp eq i32 %storemerge, 0 44 %add = add nsw i32 %storemerge, 1 45 br i1 %tobool4, label %inner.header, label %exit 46 47 exit: ; preds = %inner.latch 48 %storemerge1.lcssa = phi i32 [ %storemerge1, %inner.latch ] 49 store i32 %storemerge1.lcssa, i32* @b, align 4 50 ret void 51 52 outer.latch: ; preds = %inner.header 53 %inc9 = add nsw i32 %storemerge1, 1 54 br label %outer.header 55 } 56 57 ; This case is similar to the previous one, and has the same CFG. 58 ; The difference is that loop unrolling doesn't remove any LCSSA definition, 59 ; yet breaks LCSSA form for the outer loop. It happens because before unrolling 60 ; block inner.latch was inside outer loop (and consequently, didn't require 61 ; LCSSA definition for %x), but after unrolling it occurs out of the outer 62 ; loop, so we need to insert an LCSSA definition to keep LCSSA. 63 64 ; Function Attrs: nounwind uwtable 65 define void @fn2() { 66 entry: 67 br label %outer.header 68 69 outer.header: 70 br label %inner.header 71 72 inner.header: 73 %x = load i32, i32* undef, align 4 74 br i1 true, label %outer.latch, label %inner.latch 75 76 inner.latch: 77 %inc6 = add nsw i32 %x, 1 78 store i32 %inc6, i32* undef, align 4 79 br i1 false, label %inner.header, label %exit 80 81 exit: 82 ret void 83 84 outer.latch: 85 br label %outer.header 86 } 87
