On Mon, Sep 29, 2014 at 11:36 AM, Hal Finkel <[email protected]> wrote:
> Hi Richard, > > What does all of this suggest to you about the right design? > One more question. Given: typedef int * __attribute__((align_value(32))) *Y; ... does the attribute apply to the outer pointer or the inner pointer? (My guess: it surprisingly applies to the outer pointer.) If that's the case, then I think align_value should live entirely outside the type system, in the same way that __attribute__((aligned)) does. Note that, given: typedef int __attribute__((aligned(64))) *p __attribute__((aligned(8))) p is a 64-byte-aligned pointer to int, not an 8-byte-aligned pointer to a 64-byte-aligned int. If that's the case, I suggest you model it exactly like AlignedAttr -- as an attribute on the TypedefDecl -- and look for it explicitly in the cases where you want to use it by walking the type sugar and looking for a TypedefDecl. > FWIW, maybe creating some kind of synthetic typedef type for the return > value from DeduceTemplateArgumentsByTypeMatch would work? > > Thanks again, > Hal > > ----- Original Message ----- > > From: "Alexey Bataev" <[email protected]> > > To: "Hal Finkel" <[email protected]>, > [email protected] > > Cc: [email protected], "aaron ballman" <[email protected]>, > [email protected], [email protected] > > Sent: Friday, September 26, 2014 12:26:29 AM > > Subject: Re: [PATCH] align_value attribute in Clang > > > > 1. ICC does not create a new type for type with this attribute. All > > types are still the same. > > 2. > > > > int n __attribute__((aligned(32))); > > decltype(&n) - int*. > > > > > > Best regards, > > Alexey Bataev > > ============= > > Software Engineer > > Intel Compiler Team > > > > 26.09.2014 4:28, Hal Finkel пишет: > > > ----- Original Message ----- > > >> From: "Richard Smith" <[email protected]> > > >> To: [email protected], "aaron ballman" <[email protected]>, > > >> [email protected], [email protected], "a > > >> bataev" <[email protected]> > > >> Cc: [email protected] > > >> Sent: Thursday, September 25, 2014 7:06:33 PM > > >> Subject: Re: [PATCH] align_value attribute in Clang > > >> > > >> I'd like some more information about how ICC treats this > > >> attribute. > > >> Does it produce a new type? For instance: > > > I did a quick experiment with icc (ICC) 14.0.1 20131008 (with -Wall > > > -O3 -pedantic): > > > > > >> typedef int *I32 __attribute__((align_value(32))); > > >> typedef int *I64 __attribute__((align_value(64))); > > >> > > >> typedef I32 X; typedef I64 X; // ill-formed? > > > No diagnostic. > > > > > >> template<typename> struct Y; > > >> typedef Y<I32> Z; typedef Y<I64> Z; // ill-formed? > > > No diagnostic. > > > > > >> extern I32 i32; > > >> I64 i64 = i32; // ill-formed? Is an explicit cast required? > > > No diagnostic. > > > > > >> I32 i32 = i64; // ill-formed? Is there an implicit conversion > > >> that > > >> discards alignment? > > > No diagnostic. > > > > > > Alexey, can you please comment on the specifics? > > > > > > -Hal > > > > > >> ... and if there's an implicit conversion that discards alignment, > > >> what is its conversion rank? > > >> > > >> If I have: > > >> > > >> int n __attribute__((aligned(32))); > > >> > > >> ... then what is `decltype(&n)`? Is it `int*`, or `int* > > >> __attribute__((align_value(32)))`? > > >> > > >> http://reviews.llvm.org/D4635 > > >> > > >> > > >> > > > > > > -- > Hal Finkel > Assistant Computational Scientist > Leadership Computing Facility > Argonne National Laboratory >
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