[llvm] [LLVM][ADT] Explicitly convert size_t values to SmallVector's size type (PR #77939)

[Andrei Golubev via llvm-commits]

https://github.com/andrey-golubev updated https://github.com/llvm/llvm-project/pull/77939

>From 5e2626b0d73411e24f3324f08b4428aacfa60994 Mon Sep 17 00:00:00 2001
From: "Golubev, Andrey" <andrey.golubev at intel.com>
Date: Fri, 29 Dec 2023 15:53:17 +0000
Subject: [PATCH] [LLVM][ADT] Explicitly convert size_t values to SmallVector's
 size type

Multiple places rely on implicit conversion when assigning 'size_t' values
to the member fields (size or capacity) of SmallVector.

Depending on the platform / compiler configuration, this may result in
narrowing conversion warnings (especially given that the size type of
SmallVector's member fields is determined based on type T - in SmallVector<T>).
To avoid the problem altogether, make the conversions explicit.

Co-authored-by: Orest Chura <orest.chura at intel.com>
---
 llvm/include/llvm/ADT/SmallVector.h | 19 ++++++++++++++-----
 llvm/lib/Support/SmallVector.cpp    |  3 +--
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index 2e6d2dc6ce90a2c..09676d792dfebd8 100644
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -61,7 +61,7 @@ template <class Size_T> class SmallVectorBase {
 
   SmallVectorBase() = delete;
   SmallVectorBase(void *FirstEl, size_t TotalCapacity)
-      : BeginX(FirstEl), Capacity(TotalCapacity) {}
+      : BeginX(FirstEl), Capacity(static_cast<Size_T>(TotalCapacity)) {}
 
   /// This is a helper for \a grow() that's out of line to reduce code
   /// duplication.  This function will report a fatal error if it can't grow at
@@ -99,8 +99,18 @@ template <class Size_T> class SmallVectorBase {
   ///
   /// This does not construct or destroy any elements in the vector.
   void set_size(size_t N) {
-    assert(N <= capacity());
-    Size = N;
+    assert(N <= capacity()); // implies no overflow in assignment
+    Size = static_cast<Size_T>(N);
+  }
+
+  /// Set the array data pointer to \p Begin and capacity to \p N.
+  ///
+  /// This does not construct or destroy any elements in the vector.
+  //  This does not clean up any existing allocation.
+  void set_allocation_range(void *Begin, size_t N) {
+    assert(N <= SizeTypeMax());
+    BeginX = Begin;
+    Capacity = static_cast<Size_T>(N);
   }
 };
 
@@ -467,8 +477,7 @@ void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow(
   if (!this->isSmall())
     free(this->begin());
 
-  this->BeginX = NewElts;
-  this->Capacity = NewCapacity;
+  this->set_allocation_range(NewElts, NewCapacity);
 }
 
 /// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put
diff --git a/llvm/lib/Support/SmallVector.cpp b/llvm/lib/Support/SmallVector.cpp
index f7e7e80332cc337..b6ce37842040b36 100644
--- a/llvm/lib/Support/SmallVector.cpp
+++ b/llvm/lib/Support/SmallVector.cpp
@@ -153,8 +153,7 @@ void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize,
       NewElts = replaceAllocation(NewElts, TSize, NewCapacity, size());
   }
 
-  this->BeginX = NewElts;
-  this->Capacity = NewCapacity;
+  this->set_allocation_range(NewElts, NewCapacity);
 }
 
 template class llvm::SmallVectorBase<uint32_t>;