[llvm] [VPlan] Get GEP wrap flags from VPInstructions (NFCI). (PR #195730)

[Florian Hahn via llvm-commits]

https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/195730

>From f7e9e95f082f1a8176e69ee0b27e9fa02769076f Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Fri, 1 May 2026 20:39:53 +0100
Subject: [PATCH] [VPlan] Get GEP wrap flags from VPInstructions (NFCI).

Add helper to retrieve GEP no-wrap flags from VPInstructions, looking
through zero-index GEPs and pointer casts, like Value::stripPointerCasts.
Removes an access to underlying IR.
---
 .../Transforms/Vectorize/LoopVectorize.cpp    | 16 ++++++----------
 llvm/lib/Transforms/Vectorize/VPlanUtils.cpp  | 19 +++++++++++++++++++
 llvm/lib/Transforms/Vectorize/VPlanUtils.h    |  4 ++++
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 78163b5fe35d5..ebbaec83fdc6b 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6423,25 +6423,21 @@ VPRecipeBase *VPRecipeBuilder::tryToWidenMemory(VPInstruction *VPI,
   VPValue *Ptr = VPI->getOpcode() == Instruction::Load ? VPI->getOperand(0)
                                                        : VPI->getOperand(1);
   if (Consecutive) {
-    auto *GEP = dyn_cast<GetElementPtrInst>(
-        Ptr->getUnderlyingValue()->stripPointerCasts());
+    GEPNoWrapFlags Flags = vputils::getGEPFlagsForPtr(Ptr);
     VPSingleDefRecipe *VectorPtr;
     if (Reverse) {
       // When folding the tail, we may compute an address that we don't in the
       // original scalar loop: drop the GEP no-wrap flags in this case.
       // Otherwise preserve existing flags without no-unsigned-wrap, as we will
       // emit negative indices.
-      GEPNoWrapFlags Flags =
-          CM.foldTailByMasking() || !GEP
-              ? GEPNoWrapFlags::none()
-              : GEP->getNoWrapFlags().withoutNoUnsignedWrap();
+      GEPNoWrapFlags ReverseFlags = CM.foldTailByMasking()
+                                        ? GEPNoWrapFlags::none()
+                                        : Flags.withoutNoUnsignedWrap();
       VectorPtr = new VPVectorEndPointerRecipe(
           Ptr, &Plan.getVF(), getLoadStoreType(I),
-          /*Stride*/ -1, Flags, VPI->getDebugLoc());
+          /*Stride*/ -1, ReverseFlags, VPI->getDebugLoc());
     } else {
-      VectorPtr = new VPVectorPointerRecipe(Ptr, getLoadStoreType(I),
-                                            GEP ? GEP->getNoWrapFlags()
-                                                : GEPNoWrapFlags::none(),
+      VectorPtr = new VPVectorPointerRecipe(Ptr, getLoadStoreType(I), Flags,
                                             VPI->getDebugLoc());
     }
     Builder.setInsertPoint(VPI);
diff --git a/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp b/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
index a60b490a69ce6..af25df3965773 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
@@ -138,6 +138,25 @@ static bool poisonGuaranteesUB(const VPValue *V) {
   return false;
 }
 
+GEPNoWrapFlags vputils::getGEPFlagsForPtr(VPValue *Ptr) {
+  // Like IR stripPointerCasts, look through GEPs with all-zero indices and
+  // casts to find a root GEP VPInstruction.
+  while (auto *PtrVPI = dyn_cast<VPInstruction>(Ptr)) {
+    unsigned Opcode = PtrVPI->getOpcode();
+    if (Opcode == Instruction::GetElementPtr) {
+      if (any_of(drop_begin(PtrVPI->operands()),
+                 [](VPValue *Op) { return !match(Op, m_ZeroInt()); }))
+        return PtrVPI->getGEPNoWrapFlags();
+      Ptr = PtrVPI->getOperand(0);
+      continue;
+    }
+    if (Opcode != Instruction::BitCast && Opcode != Instruction::AddrSpaceCast)
+      break;
+    Ptr = PtrVPI->getOperand(0);
+  }
+  return GEPNoWrapFlags::none();
+}
+
 const SCEV *vputils::getSCEVExprForVPValue(const VPValue *V,
                                            PredicatedScalarEvolution &PSE,
                                            const Loop *L) {
diff --git a/llvm/lib/Transforms/Vectorize/VPlanUtils.h b/llvm/lib/Transforms/Vectorize/VPlanUtils.h
index cf54b2b6ac963..ac3a1005c8f24 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanUtils.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanUtils.h
@@ -155,6 +155,10 @@ template <typename RecipeTy> static RecipeTy *findUserOf(VPValue *V) {
 /// nullptr if not found.
 VPInstruction *findCanonicalIVIncrement(VPlan &Plan);
 
+/// Returns the GEP nowrap flags for \p Ptr, looking through pointer casts
+/// mirroring Value::stripPointerCasts.
+GEPNoWrapFlags getGEPFlagsForPtr(VPValue *Ptr);
+
 /// Find the ComputeReductionResult recipe for \p PhiR, looking through selects
 /// inserted for predicated reductions or tail folding.
 VPInstruction *findComputeReductionResult(VPReductionPHIRecipe *PhiR);