[clang] [Matrix] Preserve signedness when extending matrix index expression. (PR #103044)

[John McCall via cfe-commits]

================
@@ -4348,8 +4348,18 @@ LValue CodeGenFunction::EmitMatrixSubscriptExpr(const MatrixSubscriptExpr *E) {
       !E->isIncomplete() &&
       "incomplete matrix subscript expressions should be rejected during Sema");
   LValue Base = EmitLValue(E->getBase());
-  llvm::Value *RowIdx = EmitScalarExpr(E->getRowIdx());
-  llvm::Value *ColIdx = EmitScalarExpr(E->getColumnIdx());
+
+  // Extend or truncate the index type to 32 or 64-bits.
+  auto EmitIndex = [this](const Expr *E) {
+    llvm::Value *Idx = EmitScalarExpr(E);
+    bool IsSigned = E->getType()->isSignedIntegerOrEnumerationType();
----------------
rjmccall wrote:

You can sink this into the `if` block.

https://github.com/llvm/llvm-project/pull/103044