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Re: Restricting arguments to intrinsic functions
- From: Tejas Belagod <tejas dot belagod at arm dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>, Charles Baylis <charles dot baylis at linaro dot org>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Fri, 24 Oct 2014 16:11:04 +0100
- Subject: Re: Restricting arguments to intrinsic functions
- Authentication-results: sourceware.org; auth=none
- References: <CADnVucA8f3zHOY_UaFvxNAR-j3D7EDvTPiYpoLEUNJL+8TYZzw at mail dot gmail dot com> <20141024144446 dot GA23124 at gate dot crashing dot org>
On 24/10/14 15:44, Segher Boessenkool wrote:
On Thu, Oct 23, 2014 at 06:52:20PM +0100, Charles Baylis wrote:
( tl;dr: How do I handle intrinsic or builtin functions where there
are restrictions on the arguments which can't be represented in a C
function prototype? Do other ports have this problem, how do they
solve it? Language extension for C++98 to provide static_assert?)
In the builtin expand, you can get the operands' predicates from the
insn_data array entry for the RTL pattern generated for that builtin.
If the predicate is false, do a copy_to_mode_reg; if then the predicate
is still false, assume it had to be some constant and error out.
This works well; I stole the method from the tile* ports. It may need
tweaks for your port.
I think we already do that in the aarch64 port in aarch64-builtins.c
when we expand builtins.
/* Handle constants only if the predicate allows it. */
bool op_const_int_p =
But the accuracy of the source position, as Charles says, is lost by the
time the expander kicks in. For eg. in this piece of code,
xget_lane(int16x4_t a, int16x4_t b, int c)
return vqrdmulh_lane_s16 (a, b, 7);
$ aarch64-none-elf-gcc -O3 cr.c -S
In file included from cr.c:2:0:
In function 'xget_lane':
error: lane out of range
return __builtin_aarch64_sqrdmulh_lanev4hi (__a, __b, __c);
The diagnostic issued points to the line in arm_neon.h, but we expect
this to point to the line in cr.c. I suspect we need something closer to