[CIR][NFC] Backport refactoring of unary plus/minus handling

In the review for upstreaming unary operation support
(llvm/llvm-project#131369), it was suggested that
the VisitPlus and VisitMinus functions should be combined. This is a backport
of that refactoring.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -617,38 +617,26 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
     QualType promotionTy = PromotionType.isNull()
                                ? getPromotionType(E->getSubExpr()->getType())
                                : PromotionType;
-    auto result = VisitPlus(E, promotionTy);
+    auto result = emitUnaryPlusOrMinus(E, cir::UnaryOpKind::Plus, promotionTy);
     if (result && !promotionTy.isNull())
       return emitUnPromotedValue(result, E->getType());
     return result;
   }
 
-  mlir::Value VisitPlus(const UnaryOperator *E,
-                        QualType PromotionType = QualType()) {
-    // This differs from gcc, though, most likely due to a bug in gcc.
-    TestAndClearIgnoreResultAssign();
-
-    mlir::Value operand;
-    if (!PromotionType.isNull())
-      operand = CGF.emitPromotedScalarExpr(E->getSubExpr(), PromotionType);
-    else
-      operand = Visit(E->getSubExpr());
-
-    return emitUnaryOp(E, cir::UnaryOpKind::Plus, operand);
-  }
-
   mlir::Value VisitUnaryMinus(const UnaryOperator *E,
                               QualType PromotionType = QualType()) {
     QualType promotionTy = PromotionType.isNull()
                                ? getPromotionType(E->getSubExpr()->getType())
                                : PromotionType;
-    auto result = VisitMinus(E, promotionTy);
+    auto result = emitUnaryPlusOrMinus(E, cir::UnaryOpKind::Minus, promotionTy);
     if (result && !promotionTy.isNull())
       return emitUnPromotedValue(result, E->getType());
     return result;
   }
 
-  mlir::Value VisitMinus(const UnaryOperator *E, QualType PromotionType) {
+  mlir::Value emitUnaryPlusOrMinus(const UnaryOperator *E,
+                                   cir::UnaryOpKind kind,
+                                   QualType PromotionType) {
     TestAndClearIgnoreResultAssign();
 
     mlir::Value operand;
@@ -657,10 +645,12 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
     else
       operand = Visit(E->getSubExpr());
 
+    bool nsw =
+        kind == cir::UnaryOpKind::Minus && E->getType()->isSignedIntegerType();
+
     // NOTE: LLVM codegen will lower this directly to either a FNeg
     // or a Sub instruction.  In CIR this will be handled later in LowerToLLVM.
-    return emitUnaryOp(E, cir::UnaryOpKind::Minus, operand,
-                       /*nsw=*/E->getType()->isSignedIntegerType());
+    return emitUnaryOp(E, kind, operand, nsw);
   }
 
   mlir::Value VisitUnaryNot(const UnaryOperator *E) {
@@ -2334,9 +2324,9 @@ mlir::Value ScalarExprEmitter::emitPromoted(const Expr *E,
     case UO_Real:
       llvm_unreachable("NYI");
     case UO_Minus:
-      return VisitMinus(UO, PromotionType);
+      return emitUnaryPlusOrMinus(UO, cir::UnaryOpKind::Minus, PromotionType);
     case UO_Plus:
-      return VisitPlus(UO, PromotionType);
+      return emitUnaryPlusOrMinus(UO, cir::UnaryOpKind::Plus, PromotionType);
     default:
       break;
     }