[clang] [clang] Increase VecLib bitfield size to 4 bits in CodeGenOptions.def #3 (PR #108804)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Mainak Sil (MainakSil)

<details>
<summary>Changes</summary>

Summary:
This PR fixes the issue where the VecLib bitfield in CodeGenOptions.def is too small to accommodate the increasing number of vector libraries. Specifically, the bitfield size was previously set to 3, but with the introduction of more vector libraries (currently 9), the bitfield needed to be expanded to avoid potential issues in vectorization.

In this PR, I have increased the size of the VecLib bitfield from 3 to 4 to account for the additional libraries. This ensures that all 9 vector libraries are correctly encoded and available for use without errors.

Changes Made:
Modified: Increased the VecLib bitfield size from 3 to 4 in clang/include/clang/Basic/CodeGenOptions.def.

Motivation:
This change is necessary to ensure that all vector libraries are properly represented and selectable. The current limitation of the VecLib bitfield size was causing some vectorization opportunities to be lost when more than 3 bits were needed to represent the library options.

Closes:
Fixes https://github.com/llvm/llvm-project/issues/108704

---
Full diff: https://github.com/llvm/llvm-project/pull/108804.diff


1 Files Affected:

- (modified) clang/include/clang/Basic/CodeGenOptions.def (+6-1) 


``````````diff
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index b600198998d85b..2d5bb84d1cc59c 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -375,8 +375,13 @@ ENUM_CODEGENOPT(Inlining, InliningMethod, 2, NormalInlining)
 /// The maximum stack size a function can have to be considered for inlining.
 VALUE_CODEGENOPT(InlineMaxStackSize, 32, UINT_MAX)
 
+// Ensure the VecLib bitfield has enough space for future vector libraries.
+// If new vector libraries are added beyond the current limit of 16, this static assertion will fail.
+static_assert(static_cast<int>(llvm::driver::VectorLibrary::NoLibrary) <= 16, 
+              "The VecLib bitfield in CodeGenOptions needs to be expanded to support more vector libraries.");
+
 // Vector functions library to use.
-ENUM_CODEGENOPT(VecLib, llvm::driver::VectorLibrary, 3, llvm::driver::VectorLibrary::NoLibrary)
+ENUM_CODEGENOPT(VecLib, llvm::driver::VectorLibrary, 4, llvm::driver::VectorLibrary::NoLibrary)
 
 /// The default TLS model to use.
 ENUM_CODEGENOPT(DefaultTLSModel, TLSModel, 2, GeneralDynamicTLSModel)

``````````

</details>


https://github.com/llvm/llvm-project/pull/108804