[llvm] [LoopVectorize] Vectorize fixed-order recurrence with vscale x 1. (PR #142772)

[Mel Chen via llvm-commits]

================
@@ -8564,13 +8559,17 @@ addUsersInExitBlocks(VPlan &Plan,
 /// users in the original exit block using the VPIRInstruction wrapping to the
 /// LCSSA phi.
 static void addExitUsersForFirstOrderRecurrences(
-    VPlan &Plan, SetVector<VPIRInstruction *> &ExitUsersToFix) {
+    VPlan &Plan, SetVector<VPIRInstruction *> &ExitUsersToFix, VFRange &Range) {
   VPRegionBlock *VectorRegion = Plan.getVectorLoopRegion();
   auto *ScalarPHVPBB = Plan.getScalarPreheader();
   auto *MiddleVPBB = Plan.getMiddleBlock();
   VPBuilder ScalarPHBuilder(ScalarPHVPBB);
   VPBuilder MiddleBuilder(MiddleVPBB, MiddleVPBB->getFirstNonPhi());
 
+  auto IsScalableOne = [](ElementCount VF) -> bool {
+    return VF.isScalable() && VF.getKnownMinValue() == 1;
----------------
Mel-Chen wrote:

Sure
0efbda6ecaeada4b7d9d348112013e642d349da8

https://github.com/llvm/llvm-project/pull/142772