[llvm] [PtrUseVisitor] Allow using Argument as a starting point (PR #106308)

[Artem Belevich via llvm-commits]

https://github.com/Artem-B updated https://github.com/llvm/llvm-project/pull/106308

>From 205270e95901e9e82257e88e2a36346527f899b0 Mon Sep 17 00:00:00 2001
From: Artem Belevich <tra at google.com>
Date: Tue, 27 Aug 2024 16:20:35 -0700
Subject: [PATCH] [PtrUseVisitor] Allow using Argument as a starting point

Argument is another possible starting point for the pointer traversal,
and PtrUseVisitor should be able to handle it.
---
 llvm/include/llvm/Analysis/PtrUseVisitor.h | 7 +++++--
 llvm/lib/Analysis/PtrUseVisitor.cpp        | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/Analysis/PtrUseVisitor.h b/llvm/include/llvm/Analysis/PtrUseVisitor.h
index 86206b2d5e9f88..f19e53798da481 100644
--- a/llvm/include/llvm/Analysis/PtrUseVisitor.h
+++ b/llvm/include/llvm/Analysis/PtrUseVisitor.h
@@ -158,7 +158,7 @@ class PtrUseVisitorBase {
   ///
   /// This will visit the users with the same offset of the current visit
   /// (including an unknown offset if that is the current state).
-  void enqueueUsers(Instruction &I);
+  void enqueueUsers(Value &I);
 
   /// Walk the operands of a GEP and adjust the offset as appropriate.
   ///
@@ -209,11 +209,14 @@ class PtrUseVisitor : protected InstVisitor<DerivedT>,
 
   /// Recursively visit the uses of the given pointer.
   /// \returns An info struct about the pointer. See \c PtrInfo for details.
-  PtrInfo visitPtr(Instruction &I) {
+  /// We may also need to process Argument pointers, so the input uses is
+  /// a common Value type.
+  PtrInfo visitPtr(Value &I) {
     // This must be a pointer type. Get an integer type suitable to hold
     // offsets on this pointer.
     // FIXME: Support a vector of pointers.
     assert(I.getType()->isPointerTy());
+    assert(isa<Instruction>(I) || isa<Argument>(I));
     IntegerType *IntIdxTy = cast<IntegerType>(DL.getIndexType(I.getType()));
     IsOffsetKnown = true;
     Offset = APInt(IntIdxTy->getBitWidth(), 0);
diff --git a/llvm/lib/Analysis/PtrUseVisitor.cpp b/llvm/lib/Analysis/PtrUseVisitor.cpp
index 49304818d7efed..9c79546f491eff 100644
--- a/llvm/lib/Analysis/PtrUseVisitor.cpp
+++ b/llvm/lib/Analysis/PtrUseVisitor.cpp
@@ -17,7 +17,7 @@
 
 using namespace llvm;
 
-void detail::PtrUseVisitorBase::enqueueUsers(Instruction &I) {
+void detail::PtrUseVisitorBase::enqueueUsers(Value &I) {
   for (Use &U : I.uses()) {
     if (VisitedUses.insert(&U).second) {
       UseToVisit NewU = {