[clang] [CIR] Upstream CastOp and scalar conversions (PR #130690)

[Erich Keane via cfe-commits]

================
@@ -84,26 +96,266 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
   }
 
   mlir::Value VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *e) {
-    mlir::Type type = cgf.convertType(e->getType());
+    mlir::Type type = convertType(e->getType());
     return builder.create<cir::ConstantOp>(
         cgf.getLoc(e->getExprLoc()), type,
         builder.getCIRBoolAttr(e->getValue()));
   }
 
-  mlir::Value VisitCastExpr(CastExpr *E);
+  mlir::Value VisitCastExpr(CastExpr *e);
+
+  mlir::Value VisitExplicitCastExpr(ExplicitCastExpr *e) {
+    return VisitCastExpr(e);
+  }
+
+  /// Perform a pointer to boolean conversion.
+  mlir::Value emitPointerToBoolConversion(mlir::Value v, QualType qt) {
+    // TODO(cir): comparing the ptr to null is done when lowering CIR to LLVM.
+    // We might want to have a separate pass for these types of conversions.
+    return cgf.getBuilder().createPtrToBoolCast(v);
+  }
+
+  mlir::Value emitFloatToBoolConversion(mlir::Value src, mlir::Location loc) {
+    auto boolTy = builder.getBoolTy();
+    return builder.create<cir::CastOp>(loc, boolTy,
+                                       cir::CastKind::float_to_bool, src);
+  }
+
+  mlir::Value emitIntToBoolConversion(mlir::Value srcVal, mlir::Location loc) {
+    // Because of the type rules of C, we often end up computing a
+    // logical value, then zero extending it to int, then wanting it
+    // as a logical value again.
+    // TODO: optimize this common case here or leave it for later
+    // CIR passes?
+    mlir::Type boolTy = convertType(cgf.getContext().BoolTy);
+    return builder.create<cir::CastOp>(loc, boolTy, cir::CastKind::int_to_bool,
+                                       srcVal);
+  }
+
+  /// Convert the specified expression value to a boolean (!cir.bool) truth
+  /// value. This is equivalent to "Val != 0".
+  mlir::Value emitConversionToBool(mlir::Value src, QualType srcType,
+                                   mlir::Location loc) {
+    assert(srcType.isCanonical() && "EmitScalarConversion strips typedefs");
+
+    if (srcType->isRealFloatingType())
+      return emitFloatToBoolConversion(src, loc);
+
+    if ([[maybe_unused]] auto *mpt = llvm::dyn_cast<MemberPointerType>(srcType))
----------------
erichkeane wrote:

```suggestion
    if (llvm::isa<MemberPointerType>(srcType))
```

https://github.com/llvm/llvm-project/pull/130690