[VPlan] Also print final VPlan directly before codegen/execute. (llvm#82269)

Some optimizations are apply after UF and VF have been chosen. This
patch adds an extra print of the final VPlan just before
codegen/execution.

In the future, there will be additional transforms that are applied
later (interleaving for example).

PR: llvm#82269

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -7450,12 +7450,14 @@ LoopVectorizationPlanner::executePlan(
       (IsEpilogueVectorization || !ExpandedSCEVs) &&
       "expanded SCEVs to reuse can only be used during epilogue vectorization");
 
-  LLVM_DEBUG(dbgs() << "Executing best plan with VF=" << BestVF << ", UF=" << BestUF
-                    << '\n');
-
   if (!IsEpilogueVectorization)
     VPlanTransforms::optimizeForVFAndUF(BestVPlan, BestVF, BestUF, PSE);
 
+  LLVM_DEBUG(dbgs() << "Executing best plan with VF=" << BestVF
+                    << ", UF=" << BestUF << '\n');
+  BestVPlan.setName("Final VPlan");
+  LLVM_DEBUG(BestVPlan.dump());
+
   // Perform the actual loop transformation.
   VPTransformState State(BestVF, BestUF, LI, DT, ILV.Builder, &ILV, &BestVPlan,
                          OrigLoop->getHeader()->getContext());

llvm/test/Transforms/LoopVectorize/RISCV/riscv-vector-reverse.ll

@@ -120,7 +120,7 @@ define void @vector_reverse_i64(ptr nocapture noundef writeonly %A, ptr nocaptur
 ; CHECK-NEXT:  LV: Found a vectorizable loop (vscale x 4) in <stdin>
 ; CHECK-NEXT:  LEV: Epilogue vectorization is not profitable for this loop
 ; CHECK-NEXT:  Executing best plan with VF=vscale x 4, UF=1
-; CHECK-NEXT:  LV: Interleaving disabled by the pass manager
+; CHECK:       LV: Interleaving disabled by the pass manager
 ; CHECK-NEXT:  LV: Vectorizing: innermost loop.
 ;
 entry:
@@ -260,7 +260,7 @@ define void @vector_reverse_f32(ptr nocapture noundef writeonly %A, ptr nocaptur
 ; CHECK-NEXT:  LV: Found a vectorizable loop (vscale x 4) in <stdin>
 ; CHECK-NEXT:  LEV: Epilogue vectorization is not profitable for this loop
 ; CHECK-NEXT:  Executing best plan with VF=vscale x 4, UF=1
-; CHECK-NEXT:  LV: Interleaving disabled by the pass manager
+; CHECK:       LV: Interleaving disabled by the pass manager
 ; CHECK-NEXT:  LV: Vectorizing: innermost loop.
 ;
 entry:

llvm/test/Transforms/LoopVectorize/vplan-printing-before-execute.ll

@@ -0,0 +1,90 @@
+; RUN: opt -passes=loop-vectorize -force-vector-width=8 -force-vector-interleave=2 -disable-output -debug -S %s 2>&1 | FileCheck --check-prefixes=CHECK %s
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+
+; REQUIRES: asserts
+
+; Check if the vector loop condition can be simplified to true for a given
+; VF/IC combination.
+define void @test_tc_less_than_16(ptr %A, i64 %N) {
+; CHECK:      LV: Scalarizing:  %cmp =
+; CHECK-NEXT: VPlan 'Initial VPlan for VF={8},UF>=1' {
+; CHECK-NEXT: Live-in vp<[[VFxUF:%.+]]> = VF * UF
+; CHECK-NEXT: Live-in vp<[[VTC:%.+]]> = vector-trip-count
+; CHECK-NEXT: vp<[[TC:%.+]]> = original trip-count
+; CHECK-EMPTY:
+; CHECK-NEXT: ph:
+; CHECK-NEXT:   EMIT vp<[[TC]]> = EXPAND SCEV (zext i4 (trunc i64 %N to i4) to i64)
+; CHECK-NEXT: No successors
+; 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<[[CAN_IV_NEXT:%.+]]>
+; CHECK-NEXT:     EMIT ir<%p.src> = WIDEN-POINTER-INDUCTION ir<%A>, 1
+; CHECK-NEXT:     vp<[[VPTR:%.]]> = vector-pointer ir<%p.src>
+; CHECK-NEXT:     WIDEN ir<%l> = load vp<[[VPTR]]>
+; CHECK-NEXT:     WIDEN ir<%add> = add nsw ir<%l>, ir<10>
+; CHECK-NEXT:     vp<[[VPTR2:%.+]]> = vector-pointer ir<%p.src>
+; CHECK-NEXT:     WIDEN store vp<[[VPTR2]]>, ir<%add>
+; CHECK-NEXT:     EMIT vp<[[CAN_IV_NEXT]]> = add nuw vp<[[CAN_IV:%.+]]>, vp<[[VFxUF]]>
+; CHECK-NEXT:     EMIT branch-on-count vp<[[CAN_IV_NEXT]]>, vp<[[VTC]]>
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+; CHECK-NEXT: Successor(s): middle.block
+; CHECK-EMPTY:
+; CHECK-NEXT: middle.block:
+; CHECK-NEXT: No successors
+; CHECK-NEXT: }
+;
+; CHECK: Executing best plan with VF=8, UF=2
+; CHECK-NEXT: VPlan 'Final VPlan for VF={8},UF={2}' {
+; CHECK-NEXT: Live-in vp<[[VFxUF:%.+]]> = VF * UF
+; CHECK-NEXT: vp<[[TC:%.+]]> = original trip-count
+; CHECK-EMPTY:
+; CHECK-NEXT: ph:
+; CHECK-NEXT:   EMIT vp<[[TC]]> = EXPAND SCEV (zext i4 (trunc i64 %N to i4) to i64)
+; CHECK-NEXT: No successors
+; 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<[[CAN_IV_NEXT:%.+]]>
+; CHECK-NEXT:     EMIT ir<%p.src> = WIDEN-POINTER-INDUCTION ir<%A>, 1
+; CHECK-NEXT:     vp<[[VPTR:%.]]> = vector-pointer ir<%p.src>
+; CHECK-NEXT:     WIDEN ir<%l> = load vp<[[VPTR]]>
+; CHECK-NEXT:     WIDEN ir<%add> = add nsw ir<%l>, ir<10>
+; CHECK-NEXT:     vp<[[VPTR2:%.+]]> = vector-pointer ir<%p.src>
+; CHECK-NEXT:     WIDEN store vp<[[VPTR2]]>, ir<%add>
+; CHECK-NEXT:     EMIT vp<[[CAN_IV_NEXT]]> = add nuw vp<[[CAN_IV:%.+]]>, vp<[[VFxUF]]>
+; CHECK-NEXT:     EMIT branch-on-cond ir<true>
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+; CHECK-NEXT: Successor(s): middle.block
+; CHECK-EMPTY:
+; CHECK-NEXT: middle.block:
+; CHECK-NEXT: No successors
+; CHECK-NEXT: }
+;
+entry:
+  %and = and i64 %N, 15
+  br label %loop
+
+loop:
+  %iv = phi i64 [ %and, %entry ], [ %iv.next, %loop ]
+  %p.src = phi ptr [ %A, %entry ], [ %p.src.next, %loop ]
+  %p.src.next = getelementptr inbounds i8, ptr %p.src, i64 1
+  %l = load i8, ptr %p.src, align 1
+  %add = add nsw i8 %l, 10
+  store i8 %add, ptr %p.src
+  %iv.next = add nsw i64 %iv, -1
+  %cmp = icmp eq i64 %iv.next, 0
+  br i1 %cmp, label %exit, label %loop
+
+exit:
+  ret void
+}