[CIR] Handle character literal values (#144141)

This change adds a handler for emitting a cir.constant op when a
character literal is encountered outside an initializer expression.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -162,6 +162,12 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
         builder.getAttr<cir::FPAttr>(type, e->getValue()));
   }
 
+  mlir::Value VisitCharacterLiteral(const CharacterLiteral *e) {
+    mlir::Type ty = cgf.convertType(e->getType());
+    auto init = cir::IntAttr::get(ty, e->getValue());
+    return builder.create<cir::ConstantOp>(cgf.getLoc(e->getExprLoc()), init);
+  }
+
   mlir::Value VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *e) {
     return builder.getBool(e->getValue(), cgf.getLoc(e->getExprLoc()));
   }

clang/test/CIR/CodeGen/basic.c

@@ -309,3 +309,17 @@ size_type max_size(void) {
 // CHECK:   %6 = cir.load{{.*}} %0 : !cir.ptr<!u64i>, !u64i
 // CHECK:   cir.return %6 : !u64i
 // CHECK:   }
+
+void test_char_literal() {
+  char c;
+  c = 'X';
+}
+
+// CIR: cir.func @test_char_literal
+// CIR:   cir.const #cir.int<88>
+
+// LLVM: define void @test_char_literal()
+// LLVM:   store i8 88, ptr %{{.*}}, align 1
+
+// OGCG: define{{.*}} void @test_char_literal()
+// OGCG:   store i8 88, ptr %{{.*}}, align 1