[llvm] [VPlan] Handle WidenGEP in narrowToSingleScalars (PR #166740)
Ramkumar Ramachandra via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 10 10:12:45 PST 2025
https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/166740
>From c9d6f381d53e0157028e28a0c27a52b3e1a96f15 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 6 Nov 2025 10:24:01 +0000
Subject: [PATCH] [VPlan] Handle WidenGEP in narrowToSingleScalars
---
llvm/lib/Transforms/Vectorize/VPlan.h | 6 --
.../lib/Transforms/Vectorize/VPlanRecipes.cpp | 70 +++++++------------
.../Transforms/Vectorize/VPlanTransforms.cpp | 3 +-
.../RISCV/gather-scatter-cost.ll | 14 ++--
.../widen-gep-all-indices-invariant.ll | 12 ++--
5 files changed, 40 insertions(+), 65 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 72858e1265d86..3840b464e6c2c 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1787,12 +1787,6 @@ class LLVM_ABI_FOR_TEST VPWidenGEPRecipe : public VPRecipeWithIRFlags {
return getOperand(I + 1)->isDefinedOutsideLoopRegions();
}
- bool areAllOperandsInvariant() const {
- return all_of(operands(), [](VPValue *Op) {
- return Op->isDefinedOutsideLoopRegions();
- });
- }
-
public:
VPWidenGEPRecipe(GetElementPtrInst *GEP, ArrayRef<VPValue *> Operands)
: VPRecipeWithIRFlags(VPDef::VPWidenGEPSC, Operands, *GEP),
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 707886f873fba..76173c82209ec 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -2507,51 +2507,31 @@ void VPWidenGEPRecipe::execute(VPTransformState &State) {
// is vector-typed. Thus, to keep the representation compact, we only use
// vector-typed operands for loop-varying values.
- if (areAllOperandsInvariant()) {
- // If we are vectorizing, but the GEP has only loop-invariant operands,
- // the GEP we build (by only using vector-typed operands for
- // loop-varying values) would be a scalar pointer. Thus, to ensure we
- // produce a vector of pointers, we need to either arbitrarily pick an
- // operand to broadcast, or broadcast a clone of the original GEP.
- // Here, we broadcast a clone of the original.
- //
- // TODO: If at some point we decide to scalarize instructions having
- // loop-invariant operands, this special case will no longer be
- // required. We would add the scalarization decision to
- // collectLoopScalars() and teach getVectorValue() to broadcast
- // the lane-zero scalar value.
- SmallVector<Value *> Ops;
- for (unsigned I = 0, E = getNumOperands(); I != E; I++)
- Ops.push_back(State.get(getOperand(I), VPLane(0)));
-
- auto *NewGEP =
- State.Builder.CreateGEP(getSourceElementType(), Ops[0], drop_begin(Ops),
- "", getGEPNoWrapFlags());
- Value *Splat = State.Builder.CreateVectorSplat(State.VF, NewGEP);
- State.set(this, Splat);
- } else {
- // If the GEP has at least one loop-varying operand, we are sure to
- // produce a vector of pointers unless VF is scalar.
- // The pointer operand of the new GEP. If it's loop-invariant, we
- // won't broadcast it.
- auto *Ptr = State.get(getOperand(0), isPointerLoopInvariant());
-
- // Collect all the indices for the new GEP. If any index is
- // loop-invariant, we won't broadcast it.
- SmallVector<Value *, 4> Indices;
- for (unsigned I = 1, E = getNumOperands(); I < E; I++) {
- VPValue *Operand = getOperand(I);
- Indices.push_back(State.get(Operand, isIndexLoopInvariant(I - 1)));
- }
-
- // Create the new GEP. Note that this GEP may be a scalar if VF == 1,
- // but it should be a vector, otherwise.
- auto *NewGEP = State.Builder.CreateGEP(getSourceElementType(), Ptr, Indices,
- "", getGEPNoWrapFlags());
- assert((State.VF.isScalar() || NewGEP->getType()->isVectorTy()) &&
- "NewGEP is not a pointer vector");
- State.set(this, NewGEP);
- }
+ assert(!all_of(operands(), [](VPValue *Op) {
+ return Op->isDefinedOutsideLoopRegions();
+ }) && "Expected at least one loop-variant operand");
+
+ // If the GEP has at least one loop-varying operand, we are sure to
+ // produce a vector of pointers unless VF is scalar.
+ // The pointer operand of the new GEP. If it's loop-invariant, we
+ // won't broadcast it.
+ auto *Ptr = State.get(getOperand(0), isPointerLoopInvariant());
+
+ // Collect all the indices for the new GEP. If any index is
+ // loop-invariant, we won't broadcast it.
+ SmallVector<Value *, 4> Indices;
+ for (unsigned I = 1, E = getNumOperands(); I < E; I++) {
+ VPValue *Operand = getOperand(I);
+ Indices.push_back(State.get(Operand, isIndexLoopInvariant(I - 1)));
+ }
+
+ // Create the new GEP. Note that this GEP may be a scalar if VF == 1,
+ // but it should be a vector, otherwise.
+ auto *NewGEP = State.Builder.CreateGEP(getSourceElementType(), Ptr, Indices,
+ "", getGEPNoWrapFlags());
+ assert((State.VF.isScalar() || NewGEP->getType()->isVectorTy()) &&
+ "NewGEP is not a pointer vector");
+ State.set(this, NewGEP);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index f5bef08fafcdc..eee1892010ff8 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -1391,7 +1391,8 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) {
- if (!isa<VPWidenRecipe, VPWidenSelectRecipe, VPReplicateRecipe>(&R))
+ if (!isa<VPWidenRecipe, VPWidenSelectRecipe, VPWidenGEPRecipe,
+ VPReplicateRecipe>(&R))
continue;
auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
if (RepR && (RepR->isSingleScalar() || RepR->isPredicated()))
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/gather-scatter-cost.ll b/llvm/test/Transforms/LoopVectorize/RISCV/gather-scatter-cost.ll
index 212a5c99676f4..877484f5159fd 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/gather-scatter-cost.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/gather-scatter-cost.ll
@@ -63,7 +63,7 @@ define void @predicated_uniform_load(ptr %src, i32 %n, ptr %dst, i1 %cond) {
; CHECK-NEXT: store i32 [[STORE]], ptr [[NBRBOXES]], align 4
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp sgt i32 [[IV]], [[IBOX]]
-; CHECK-NEXT: br i1 [[EXITCOND]], label [[EXIT]], label [[LOOP]], !llvm.loop [[LOOP9:![0-9]+]]
+; CHECK-NEXT: br i1 [[EXITCOND]], label [[EXIT]], label [[LOOP]], !llvm.loop [[LOOP8:![0-9]+]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
@@ -114,7 +114,7 @@ define void @predicated_strided_store(ptr %start) {
; RVA23-NEXT: [[AVL_NEXT]] = sub nuw i64 [[AVL]], [[TMP3]]
; RVA23-NEXT: [[VEC_IND_NEXT]] = add <vscale x 8 x i64> [[VEC_IND]], [[BROADCAST_SPLAT]]
; RVA23-NEXT: [[TMP7:%.*]] = icmp eq i64 [[AVL_NEXT]], 0
-; RVA23-NEXT: br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP10:![0-9]+]]
+; RVA23-NEXT: br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
; RVA23: middle.block:
; RVA23-NEXT: br label [[LOOP:%.*]]
; RVA23: exit:
@@ -141,7 +141,7 @@ define void @predicated_strided_store(ptr %start) {
; RVA23ZVL1024B-NEXT: [[AVL_NEXT]] = sub nuw i64 [[AVL]], [[TMP3]]
; RVA23ZVL1024B-NEXT: [[VEC_IND_NEXT]] = add <vscale x 2 x i64> [[VEC_IND]], [[BROADCAST_SPLAT]]
; RVA23ZVL1024B-NEXT: [[TMP7:%.*]] = icmp eq i64 [[AVL_NEXT]], 0
-; RVA23ZVL1024B-NEXT: br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP10:![0-9]+]]
+; RVA23ZVL1024B-NEXT: br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
; RVA23ZVL1024B: middle.block:
; RVA23ZVL1024B-NEXT: br label [[LOOP:%.*]]
; RVA23ZVL1024B: exit:
@@ -185,16 +185,16 @@ define void @store_to_addr_generated_from_invariant_addr(ptr noalias %p0, ptr no
; CHECK-NEXT: [[TMP5:%.*]] = getelementptr i32, ptr [[P1:%.*]], <vscale x 2 x i64> [[VEC_IND]]
; CHECK-NEXT: call void @llvm.vp.scatter.nxv2p0.nxv2p0(<vscale x 2 x ptr> [[BROADCAST_SPLAT1]], <vscale x 2 x ptr> align 8 [[TMP5]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP3]])
; CHECK-NEXT: [[TMP6:%.*]] = load i64, ptr [[P2:%.*]], align 4
-; CHECK-NEXT: [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[TMP6]], i64 0
-; CHECK-NEXT: [[BROADCAST_SPLAT2:%.*]] = shufflevector <vscale x 2 x i64> [[BROADCAST_SPLATINSERT1]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
-; CHECK-NEXT: [[TMP7:%.*]] = getelementptr i8, ptr [[P3:%.*]], <vscale x 2 x i64> [[BROADCAST_SPLAT2]]
+; CHECK-NEXT: [[TMP8:%.*]] = getelementptr i8, ptr [[P3:%.*]], i64 [[TMP6]]
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT3:%.*]] = insertelement <vscale x 2 x ptr> poison, ptr [[TMP8]], i64 0
+; CHECK-NEXT: [[TMP7:%.*]] = shufflevector <vscale x 2 x ptr> [[BROADCAST_SPLATINSERT3]], <vscale x 2 x ptr> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: call void @llvm.vp.scatter.nxv2i32.nxv2p0(<vscale x 2 x i32> zeroinitializer, <vscale x 2 x ptr> align 4 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP3]])
; CHECK-NEXT: call void @llvm.vp.scatter.nxv2i32.nxv2p0(<vscale x 2 x i32> zeroinitializer, <vscale x 2 x ptr> align 4 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP3]])
; CHECK-NEXT: call void @llvm.vp.scatter.nxv2i8.nxv2p0(<vscale x 2 x i8> zeroinitializer, <vscale x 2 x ptr> align 1 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP3]])
; CHECK-NEXT: [[AVL_NEXT]] = sub nuw i64 [[AVL]], [[TMP4]]
; CHECK-NEXT: [[VEC_IND_NEXT]] = add <vscale x 2 x i64> [[VEC_IND]], [[BROADCAST_SPLAT]]
; CHECK-NEXT: [[TMP9:%.*]] = icmp eq i64 [[AVL_NEXT]], 0
-; CHECK-NEXT: br i1 [[TMP9]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP11:![0-9]+]]
+; CHECK-NEXT: br i1 [[TMP9]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP10:![0-9]+]]
; CHECK: middle.block:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: exit:
diff --git a/llvm/test/Transforms/LoopVectorize/widen-gep-all-indices-invariant.ll b/llvm/test/Transforms/LoopVectorize/widen-gep-all-indices-invariant.ll
index d08ca8c99e8ba..c37bf74f9c1b0 100644
--- a/llvm/test/Transforms/LoopVectorize/widen-gep-all-indices-invariant.ll
+++ b/llvm/test/Transforms/LoopVectorize/widen-gep-all-indices-invariant.ll
@@ -8,14 +8,14 @@ define void @pr63340(ptr %A, ptr %B) {
; CHECK-NEXT: br label [[VECTOR_PH:%.*]]
; CHECK: vector.ph:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[A]], i64 1
-; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x ptr> poison, ptr [[TMP0]], i64 0
-; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <4 x ptr> [[DOTSPLATINSERT]], <4 x ptr> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x ptr> poison, ptr [[TMP0]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x ptr> [[BROADCAST_SPLATINSERT]], <4 x ptr> poison, <4 x i32> zeroinitializer
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[OFFSET_IDX:%.*]] = trunc i32 [[INDEX]] to i8
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds ptr, ptr [[B]], i8 [[OFFSET_IDX]]
-; CHECK-NEXT: store <4 x ptr> [[DOTSPLAT]], ptr [[TMP1]], align 8
+; CHECK-NEXT: store <4 x ptr> [[BROADCAST_SPLAT]], ptr [[TMP1]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 4
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[INDEX_NEXT]], 128
; CHECK-NEXT: br i1 [[TMP2]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
@@ -55,11 +55,11 @@ define void @wide_gep_index_invariant(ptr noalias %dst, ptr noalias %src, i64 %n
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[SRC]], align 8
-; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x ptr> poison, ptr [[TMP0]], i64 0
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr float, ptr [[TMP0]], i64 [[N]]
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x ptr> poison, ptr [[TMP1]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x ptr> [[BROADCAST_SPLATINSERT]], <4 x ptr> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT: [[TMP1:%.*]] = getelementptr float, <4 x ptr> [[BROADCAST_SPLAT]], i64 [[N]]
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr ptr, ptr [[DST]], i64 [[INDEX]]
-; CHECK-NEXT: store <4 x ptr> [[TMP1]], ptr [[TMP2]], align 8
+; CHECK-NEXT: store <4 x ptr> [[BROADCAST_SPLAT]], ptr [[TMP2]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i64 [[INDEX_NEXT]], 100
; CHECK-NEXT: br i1 [[TMP3]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
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