[LV] FoldTail w/o Primary Induction
Introduce a new VPWidenCanonicalIVRecipe to generate a canonical vector
induction for use in fold-tail-with-masking, if a primary induction is absent.
The canonical scalar IV having start = 0 and step = VF*UF, created during code
-gen to control the vector loop, is widened into a canonical vector IV having
start = {<Part*VF, Part*VF+1, ..., Part*VF+VF-1> for 0 <= Part < UF} and
step = <VF*UF, VF*UF, ..., VF*UF>.
Differential Revision: https://reviews.llvm.org/D77635
diff --git a/llvm/test/Transforms/LoopVectorize/tail-folding-counting-down.ll b/llvm/test/Transforms/LoopVectorize/tail-folding-counting-down.ll
index 2667bfe..b51cb56 100644
--- a/llvm/test/Transforms/LoopVectorize/tail-folding-counting-down.ll
+++ b/llvm/test/Transforms/LoopVectorize/tail-folding-counting-down.ll
@@ -1,12 +1,11 @@
-; RUN: opt < %s -loop-vectorize -prefer-predicate-over-epilog -S | FileCheck %s
+; RUN: opt < %s -loop-vectorize -prefer-predicate-over-epilog -force-vector-width=4 -S | FileCheck %s
-; Check that when we can't predicate this loop that it is still vectorised (with
-; an epilogue).
-; TODO: the reason this can't be predicated is because a primary induction
-; variable can't be found (not yet) for this counting down loop. But with that
-; fixed, this should be able to be predicated.
+; Check that a counting-down loop which has no primary induction variable
+; is vectorized with preferred predication.
; CHECK-LABEL: vector.body:
+; CHECK-LABEL: middle.block:
+; CHECK-NEXT: br i1 true,
target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"