[llvm] [Support] Add SpecificBumpPtrAllocator::identifyObject (PR #100475)

[Alex Langford via llvm-commits]

https://github.com/bulbazord created https://github.com/llvm/llvm-project/pull/100475

This already exists in BumpPtrAllocatorImpl, but I would like to use it from SpecificBumpPtrAllocator.

I also noticed there was no test for identifyObject so I added one.

>From cf13933543ecbe5eb2801b53e7328ace5900320a Mon Sep 17 00:00:00 2001
From: Alex Langford <alangford at apple.com>
Date: Wed, 24 Jul 2024 14:35:08 -0700
Subject: [PATCH] [Support] Add SpecificBumpPtrAllocator::identifyObject

This already exists in BumpPtrAllocatorImpl, but I would like to use it
from SpecificBumpPtrAllocator.

I also noticed there was no test for identifyObject so I added one.
---
 llvm/include/llvm/Support/Allocator.h    |  7 +++++++
 llvm/unittests/Support/AllocatorTest.cpp | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/llvm/include/llvm/Support/Allocator.h b/llvm/include/llvm/Support/Allocator.h
index eb6c4d3668550..e05f0ec0e8704 100644
--- a/llvm/include/llvm/Support/Allocator.h
+++ b/llvm/include/llvm/Support/Allocator.h
@@ -435,6 +435,13 @@ template <typename T> class SpecificBumpPtrAllocator {
 
   /// Allocate space for an array of objects without constructing them.
   T *Allocate(size_t num = 1) { return Allocator.Allocate<T>(num); }
+
+  /// \return An index uniquely and reproducibly identifying
+  /// an input pointer \p Ptr in the given allocator.
+  /// Returns an empty optional if the pointer is not found in the allocator.
+  std::optional<int64_t> identifyObject(const void *Ptr) {
+    return Allocator.identifyObject(Ptr);
+  }
 };
 
 } // end namespace llvm
diff --git a/llvm/unittests/Support/AllocatorTest.cpp b/llvm/unittests/Support/AllocatorTest.cpp
index b361b0aa72529..a82312a60229f 100644
--- a/llvm/unittests/Support/AllocatorTest.cpp
+++ b/llvm/unittests/Support/AllocatorTest.cpp
@@ -208,6 +208,19 @@ TEST(AllocatorTest, TestSlowerSlabGrowthDelay) {
   EXPECT_EQ(SlabSize * GrowthDelay + SlabSize * 2, Alloc.getTotalMemory());
 }
 
+TEST(AllocatorTest, TestIdentifyObject) {
+  BumpPtrAllocator Alloc;
+
+  uint64_t *a = (uint64_t *)Alloc.Allocate(sizeof(uint64_t), alignof(uint64_t));
+  std::optional<int64_t> maybe_a_belongs = Alloc.identifyObject(a);
+  EXPECT_TRUE(maybe_a_belongs.has_value());
+  EXPECT_TRUE(*maybe_a_belongs >= 0);
+
+  uint64_t *b = nullptr;
+  std::optional<int64_t> maybe_b_belongs = Alloc.identifyObject(b);
+  EXPECT_FALSE(maybe_b_belongs);
+}
+
 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 // easy portable way to do this, so this is kind of a hack.
 class MockSlabAllocator {