[llvm] [LV] Use IVUpdateMayOverflow to set HasNUW. (PR #111758)

[Florian Hahn via llvm-commits]

https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/111758

>From f25fd0bda8a48ef902046dc76ed2557534de01ce Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 9 Oct 2024 21:36:58 +0100
Subject: [PATCH 1/2] [LV] Use IVUpdateMayOverflow to set HasNUW.

If IVUpdateMayOverflow is false, we proved that the induction increment
cannot overflow in the vector loop. This allows setting NUW in some
cases when folding the tail.
---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp          | 9 ++++++---
 .../LoopVectorize/ARM/tail-folding-loop-hint.ll          | 2 +-
 llvm/test/Transforms/LoopVectorize/RISCV/pr88802.ll      | 2 +-
 llvm/test/Transforms/LoopVectorize/X86/pr81872.ll        | 2 +-
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index e8653498d32a12..620bcad4f6bb9c 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9014,9 +9014,12 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
 
   DebugLoc DL = getDebugLocFromInstOrOperands(Legal->getPrimaryInduction());
   TailFoldingStyle Style = CM.getTailFoldingStyle(IVUpdateMayOverflow);
-  // When not folding the tail, we know that the induction increment will not
-  // overflow.
-  bool HasNUW = Style == TailFoldingStyle::None;
+  // Use NUW for the induction increment if we proved that it won't overflow in
+  // the vector loop or when not folding the tail. Then we know that the
+  // induction increment will not overflow as the vector trip count is >=
+  // increment and a multiple of the increment.
+  bool HasNUW = !IVUpdateMayOverflow || Style == TailFoldingStyle::None;
+  ;
   addCanonicalIVRecipes(*Plan, Legal->getWidestInductionType(), HasNUW, DL);
 
   VPRecipeBuilder RecipeBuilder(*Plan, OrigLoop, TLI, Legal, CM, PSE, Builder);
diff --git a/llvm/test/Transforms/LoopVectorize/ARM/tail-folding-loop-hint.ll b/llvm/test/Transforms/LoopVectorize/ARM/tail-folding-loop-hint.ll
index 77cc3b70edb939..573a9f75f30549 100644
--- a/llvm/test/Transforms/LoopVectorize/ARM/tail-folding-loop-hint.ll
+++ b/llvm/test/Transforms/LoopVectorize/ARM/tail-folding-loop-hint.ll
@@ -50,7 +50,7 @@ define dso_local void @predicate_loop_hint(ptr noalias nocapture %A, ptr noalias
 ; CHECK:         %[[WML2:.*]] = call <4 x i32> @llvm.masked.load.v4i32.p0({{.*}}<4 x i1> %active.lane.mask
 ; CHECK:         %[[ADD:.*]] = add nsw <4 x i32> %[[WML2]], %[[WML1]]
 ; CHECK:         call void @llvm.masked.store.v4i32.p0(<4 x i32> %[[ADD]], {{.*}}<4 x i1> %active.lane.mask
-; CHECK:         %index.next = add i64 %index, 4
+; CHECK:         %index.next = add nuw i64 %index, 4
 ; CHECK:         br i1 %{{.*}}, label %{{.*}}, label %vector.body, !llvm.loop [[VEC_LOOP2:![0-9]+]]
 ;
 ; CHECK:         br i1 %{{.*}}, label %{{.*}}, label %for.body, !llvm.loop [[SCALAR_LOOP2:![0-9]+]]
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/pr88802.ll b/llvm/test/Transforms/LoopVectorize/RISCV/pr88802.ll
index f63b1b73dc522b..e4d063a3ea62fa 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/pr88802.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/pr88802.ll
@@ -55,7 +55,7 @@ define void @test(ptr %p, i64 %a, i8 %b) {
 ; CHECK-NEXT:    br label [[PRED_STORE_CONTINUE8]]
 ; CHECK:       pred.store.continue8:
 ; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <4 x i32> [[VEC_IND]], <i32 4, i32 4, i32 4, i32 4>
-; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 4
 ; CHECK-NEXT:    br i1 true, label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY1]], !llvm.loop [[LOOP0:![0-9]+]]
 ; CHECK:       middle.block:
 ; CHECK-NEXT:    br i1 true, label [[EXIT:%.*]], label [[SCALAR_PH]]
diff --git a/llvm/test/Transforms/LoopVectorize/X86/pr81872.ll b/llvm/test/Transforms/LoopVectorize/X86/pr81872.ll
index 3f38abc75a5837..a332f6954332c9 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/pr81872.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/pr81872.ll
@@ -35,7 +35,7 @@ define void @test(ptr noundef align 8 dereferenceable_or_null(16) %arr) #0 {
 ; CHECK-NEXT:    [[TMP8:%.*]] = getelementptr i64, ptr [[TMP7]], i32 -3
 ; CHECK-NEXT:    [[REVERSE:%.*]] = shufflevector <4 x i1> [[TMP4]], <4 x i1> poison, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
 ; CHECK-NEXT:    call void @llvm.masked.store.v4i64.p0(<4 x i64> <i64 1, i64 1, i64 1, i64 1>, ptr [[TMP8]], i32 8, <4 x i1> [[REVERSE]])
-; CHECK-NEXT:    [[INDEX_NEXT]] = add i64 [[INDEX]], 4
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
 ; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <4 x i64> [[VEC_IND]], <i64 -4, i64 -4, i64 -4, i64 -4>
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i64 [[INDEX_NEXT]], 12
 ; CHECK-NEXT:    br i1 [[TMP9]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !prof [[PROF1:![0-9]+]], !llvm.loop [[LOOP2:![0-9]+]]

>From 8c815fbdff8fc12e7ca872f91d935e63f3412656 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Tue, 22 Oct 2024 00:53:54 +0100
Subject: [PATCH 2/2] !fixup remove stray ;

---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 620bcad4f6bb9c..2b484af56cd824 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9019,7 +9019,6 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   // induction increment will not overflow as the vector trip count is >=
   // increment and a multiple of the increment.
   bool HasNUW = !IVUpdateMayOverflow || Style == TailFoldingStyle::None;
-  ;
   addCanonicalIVRecipes(*Plan, Legal->getWidestInductionType(), HasNUW, DL);
 
   VPRecipeBuilder RecipeBuilder(*Plan, OrigLoop, TLI, Legal, CM, PSE, Builder);