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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Andrei Golubev (andrey-golubev)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/77939.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/SmallVector.h (+5-4) 


``````````diff
diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index 2e6d2dc6ce90a2..65e862911522a8 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 +99,9 @@ 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;
+    auto n = static_cast<Size_T>(N);
+    assert(n <= capacity());
+    Size = n;
   }
 };
 
@@ -468,7 +469,7 @@ void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow(
     free(this->begin());
 
   this->BeginX = NewElts;
-  this->Capacity = NewCapacity;
+  this->Capacity = static_cast<SmallVectorSizeType<T>>(NewCapacity);
 }
 
 /// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put

``````````

</details>


https://github.com/llvm/llvm-project/pull/77939