[CIR] Upstream handling of integral-to-pointer casts (#161653)

Fix #153658

Handle integral to pointer casts and port the relevant `cast.cpp` test
cases from incubator.

Author: kimsh02

clang/include/clang/CIR/Dialect/IR/CIRDataLayout.h

@@ -14,6 +14,7 @@
 
 #include "mlir/Dialect/DLTI/DLTI.h"
 #include "mlir/IR/BuiltinOps.h"
+#include "clang/CIR/Dialect/IR/CIRTypes.h"
 
 namespace cir {
 
@@ -81,6 +82,18 @@ class CIRDataLayout {
   }
 
   llvm::TypeSize getTypeSizeInBits(mlir::Type ty) const;
+
+  llvm::TypeSize getPointerTypeSizeInBits(mlir::Type ty) const {
+    assert(mlir::isa<cir::PointerType>(ty) &&
+           "This should only be called with a pointer type");
+    return layout.getTypeSizeInBits(ty);
+  }
+
+  mlir::Type getIntPtrType(mlir::Type ty) const {
+    assert(mlir::isa<cir::PointerType>(ty) && "Expected pointer type");
+    return cir::IntType::get(ty.getContext(), getPointerTypeSizeInBits(ty),
+                             false);
+  }
 };
 
 } // namespace cir

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -1893,6 +1893,28 @@ mlir::Value ScalarExprEmitter::VisitCastExpr(CastExpr *ce) {
     }
     return v;
   }
+  case CK_IntegralToPointer: {
+    mlir::Type destCIRTy = cgf.convertType(destTy);
+    mlir::Value src = Visit(const_cast<Expr *>(subExpr));
+
+    // Properly resize by casting to an int of the same size as the pointer.
+    // Clang's IntegralToPointer includes 'bool' as the source, but in CIR
+    // 'bool' is not an integral type.  So check the source type to get the
+    // correct CIR conversion.
+    mlir::Type middleTy = cgf.cgm.getDataLayout().getIntPtrType(destCIRTy);
+    mlir::Value middleVal = builder.createCast(
+        subExpr->getType()->isBooleanType() ? cir::CastKind::bool_to_int
+                                            : cir::CastKind::integral,
+        src, middleTy);
+
+    if (cgf.cgm.getCodeGenOpts().StrictVTablePointers) {
+      cgf.cgm.errorNYI(subExpr->getSourceRange(),
+                       "IntegralToPointer: strict vtable pointers");
+      return {};
+    }
+
+    return builder.createIntToPtr(middleVal, destCIRTy);
+  }
 
   case CK_ArrayToPointerDecay:
     return cgf.emitArrayToPointerDecay(subExpr).getPointer();

clang/test/CIR/CodeGen/cast.cpp

@@ -131,3 +131,36 @@ void bitcast() {
 
 // LLVM: %[[D_VEC:.*]] = load <2 x double>, ptr {{.*}}, align 16
 // LLVM: %[[I_VEC:.*]] = bitcast <2 x double> %[[D_VEC]] to <4 x i32>
+
+void f(long int start) {
+  void *p = (void*)start;
+}
+// CIR: %[[L:.*]] = cir.load {{.*}} : !cir.ptr<!s64i>, !s64i
+// CIR: %[[MID:.*]] = cir.cast integral %[[L]] : !s64i -> !u64i
+// CIR:          cir.cast int_to_ptr %[[MID]] : !u64i -> !cir.ptr<!void>
+
+// LLVM-LABEL: define{{.*}} void @_Z1fl(i64 %0)
+// LLVM: %[[ADDR:.*]] = alloca i64, i64 1, align 8
+// LLVM: %[[PADDR:.*]] = alloca ptr, i64 1, align 8
+// LLVM: store i64 %0, ptr %[[ADDR]], align 8
+// LLVM: %[[L:.*]] = load i64, ptr %[[ADDR]], align 8
+// LLVM: %[[PTR:.*]] = inttoptr i64 %[[L]] to ptr
+// LLVM: store ptr %[[PTR]], ptr %[[PADDR]], align 8
+// LLVM: ret void
+
+struct A { int x; };
+
+void int_cast(long ptr) {
+  ((A *)ptr)->x = 0;
+}
+// CIR: cir.cast int_to_ptr {{.*}} : !u64i -> !cir.ptr<!rec_A>
+// LLVM: inttoptr {{.*}} to ptr
+
+void null_cast(long) {
+  *(int *)0 = 0;
+  ((A *)0)->x = 0;
+}
+// CIR:    %[[NULLPTR:.*]] = cir.const #cir.ptr<null> : !cir.ptr<!s32i>
+// CIR:    cir.store{{.*}} %{{.*}}, %[[NULLPTR]] : !s32i, !cir.ptr<!s32i>
+// CIR:    %[[NULLPTR_A:.*]] = cir.const #cir.ptr<null> : !cir.ptr<!rec_A>
+// CIR:    %[[A_X:.*]] = cir.get_member %[[NULLPTR_A]][0] {name = "x"} : !cir.ptr<!rec_A> -> !cir.ptr<!s32i>