yaxunl marked 3 inline comments as done.
yaxunl added inline comments.
================
Comment at: lib/CodeGen/CGExprConstant.cpp:1340
+ return C;
+ return getNullPtr(PT, DestType);
}
----------------
yaxunl wrote:
> rjmccall wrote:
> > efriedma wrote:
> > > Consider code like the following:
> > >
> > > int x = 0;
> > > auto y1 = (__specialaddrspace int*)0;
> > > auto y2 = (__specialaddrspace int*)((void)0, 0);
> > > auto y3 = (__specialaddrspace int*)x;
> > >
> > > How do you expect these three cases to behave? (The first case involves
> > > a C null pointer constant, the second and third cases are different ways
> > > of writing a general int->ptr conversion.)
> > Yeah, I think you probably need to fix APValue to be unambiguous about
> > whether the value is a formal null pointer (CK_NullToPointer) or just a
> > cast of an integer (CK_IntegralToPointer). It looks like
> > PointerExprEvaluator will generate the exact same value for both.
> It seems the current implementation generates the correct IR.
>
> I tried the following sample and I saw correct IR generated.
>
>
> ```
> private int* test_cast_0_to_ptr(void) {
> return (private int*)0;
> }
>
> private int* test_cast_int_to_ptr1(void) {
> return (private int*)((void)0, 0);
> }
>
> private int* test_cast_int_to_ptr2(void) {
> int x = 0;
> return (private int*)x;
> }
>
> ```
>
> The dumped AST is
>
>
> ```
> |-FunctionDecl 0x95fdc88 <ptr.cl:3:1, line:5:1> line:3:14 test_cast_0_to_ptr
> 'int *(void)'
> | `-CompoundStmt 0x95fdde8 <col:39, line:5:1>
> | `-ReturnStmt 0x95fddd0 <line:4:3, col:24>
> | `-CStyleCastExpr 0x95fdda8 <col:10, col:24> 'int *' <NullToPointer>
> | `-IntegerLiteral 0x95fdd70 <col:24> 'int' 0
> |-FunctionDecl 0x95fdea0 <line:13:1, line:15:1> line:13:14
> test_cast_int_to_ptr1 'int *(void)'
> | `-CompoundStmt 0x95fe098 <col:42, line:15:1>
> | `-ReturnStmt 0x95fe080 <line:14:3, col:35>
> | `-CStyleCastExpr 0x95fe058 <col:10, col:35> 'int *' <IntegralToPointer>
> | `-ParenExpr 0x95fe038 <col:24, col:35> 'int'
> | `-BinaryOperator 0x95fe010 <col:25, col:34> 'int' ','
> | |-CStyleCastExpr 0x95fdf78 <col:25, col:31> 'void' <ToVoid>
> | | `-IntegerLiteral 0x95fdf48 <col:31> 'int' 0
> | `-IntegerLiteral 0x95fdfa0 <col:34> 'int' 0
> `-FunctionDecl 0x95fe150 <line:19:1, line:22:1> line:19:14
> test_cast_int_to_ptr2 'int *(void)'
> `-CompoundStmt 0x9620130 <col:42, line:22:1>
> |-DeclStmt 0x9620080 <line:20:3, col:12>
> | `-VarDecl 0x95fe210 <col:3, col:11> col:7 used x 'int' cinit
> | `-IntegerLiteral 0x9620060 <col:11> 'int' 0
> `-ReturnStmt 0x9620118 <line:21:3, col:24>
> `-CStyleCastExpr 0x96200f0 <col:10, col:24> 'int *' <IntegralToPointer>
> ```
>
> Since only CK_NullToPointer is translated to null pointer through getNullPtr,
> CK_IntegralToPointer will result in either zero-valued pointer or inttoptr,
> the generated IR is correct.
Basically in the second and third case the destination type is not pointer, so
they do not need to be emitted as null pointer. If a literal 0 is casted to a
pointer type, then it should be emitted as a null pointer.
https://reviews.llvm.org/D26196
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
