[llvm] [LV] Vectorize early exit loops with multiple exits. (PR #174864)

[Florian Hahn via llvm-commits]

================
@@ -241,7 +241,64 @@ exit:
 }
 
 define i64 @two_early_exits_same_exit_with_constant_live_outs() {
-; CHECK: LV: Not vectorizing:  Auto-vectorization of loops with multiple uncountable early exits is not yet supported.
+; CHECK:      VPlan 'Initial VPlan for VF={4},UF>=1' {
+; CHECK-NEXT: Live-in vp<[[VF:%.+]]> = VF
+; CHECK-NEXT: Live-in vp<[[VFxUF:%.+]]> = VF * UF
+; CHECK-NEXT: Live-in vp<[[VTC:%.+]]> = vector-trip-count
+; CHECK-NEXT: Live-in ir<67> = original trip-count
+; CHECK-EMPTY:
+; CHECK-NEXT: ir-bb<entry>:
+; CHECK-NEXT:   IR   %A = alloca [1024 x i8], align 1
+; CHECK-NEXT:   IR   %B = alloca [1024 x i8], align 1
+; CHECK-NEXT:   IR   call void @init(ptr %A, i64 1024)
+; CHECK-NEXT:   IR   call void @init(ptr %B, i64 1024)
+; CHECK-NEXT: Successor(s): scalar.ph, vector.ph
+; CHECK-EMPTY:
+; CHECK-NEXT: vector.ph:
+; CHECK-NEXT: Successor(s): vector loop
+; CHECK-EMPTY:
+; CHECK-NEXT: <x1> vector loop: {
+; CHECK-NEXT:   vector.body:
+; CHECK-NEXT:     EMIT vp<[[CAN_IV:%.+]]> = CANONICAL-INDUCTION ir<0>, vp<%index.next>
+; CHECK-NEXT:     vp<[[SCALAR_STEPS:%.+]]> = SCALAR-STEPS vp<[[CAN_IV]]>, ir<1>, vp<[[VF]]>
+; CHECK-NEXT:     CLONE ir<%gep.A> = getelementptr inbounds ir<%A>, vp<[[SCALAR_STEPS]]>
+; CHECK-NEXT:     vp<[[PTRA:%.+]]> = vector-pointer inbounds ir<%gep.A>
+; CHECK-NEXT:     WIDEN ir<%ld.A> = load vp<[[PTRA]]>
+; CHECK-NEXT:     WIDEN ir<%cmp1> = icmp eq ir<%ld.A>, ir<42>
+; CHECK-NEXT:     CLONE ir<%gep.B> = getelementptr inbounds ir<%B>, vp<[[SCALAR_STEPS]]>
+; CHECK-NEXT:     vp<[[PTRB:%.+]]> = vector-pointer inbounds ir<%gep.B>
+; CHECK-NEXT:     WIDEN ir<%ld.B> = load vp<[[PTRB]]>
+; CHECK-NEXT:     WIDEN ir<%cmp2> = icmp eq ir<%ld.A>, ir<%ld.B>
+; CHECK-NEXT:     EMIT vp<%index.next> = add nuw vp<[[CAN_IV]]>, vp<[[VFxUF]]>
+; CHECK-NEXT:     EMIT vp<[[OR:%.+]]> = or ir<%cmp1>, ir<%cmp2>
+; CHECK-NEXT:     EMIT vp<[[ANY_OF:%.+]]> = any-of vp<[[OR]]>
+; CHECK-NEXT:     EMIT vp<[[CMP:%.+]]> = icmp eq vp<%index.next>, vp<[[VTC]]>
+; CHECK-NEXT:     EMIT branch-on-two-conds vp<[[ANY_OF]]>, vp<[[CMP]]>
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+; CHECK-NEXT: Successor(s): vector.early.exit, middle.block
+; CHECK-EMPTY:
+; CHECK-NEXT: middle.block:
+; CHECK-NEXT:   EMIT vp<%cmp.n> = icmp eq ir<67>, vp<[[VTC]]>
+; CHECK-NEXT:   EMIT branch-on-cond vp<%cmp.n>
+; CHECK-NEXT: Successor(s): ir-bb<exit>, scalar.ph
+; CHECK-EMPTY:
+; CHECK-NEXT: vector.early.exit:
+; CHECK-NEXT:   EMIT vp<%first.active.lane> = first-active-lane vp<[[OR]]>
+; CHECK-NEXT:   EMIT vp<%exit.cond.at.lane> = extract-lane vp<%first.active.lane>, ir<%cmp1>
+; CHECK-NEXT:   EMIT branch-on-cond vp<%exit.cond.at.lane>
+; CHECK-NEXT: Successor(s): vector.early.exit, vector.early.exit
+; CHECK-EMPTY:
+; CHECK-NEXT: vector.early.exit:
+; CHECK-NEXT: Successor(s): ir-bb<exit>
+; CHECK-EMPTY:
+; CHECK-NEXT: vector.early.exit:
----------------
fhahn wrote:

Yep, added a suffix when there is more than one exit, thanks. We may want to ensure we have unique names for blocks when printing, similar how we do it when printing VPValues.

https://github.com/llvm/llvm-project/pull/174864