[PATCH 1/2][AArch64] Simplify patterns for sshr_n_[us]64 intrinsic

Alan Lawrence alan.lawrence@arm.com
Mon Sep 8 16:20:00 GMT 2014


Patch attached.

Alan Lawrence wrote:
> The sshr_n_64 intrinsics allow performing a signed shift right by 64 places. The 
> standard ashrdi3 pattern masks the sign amount with 63, so cannot be used. 
> However, such a shift fills the result by the sign bit, which is identical to 
> shifting right by 63. This patch just simplifies the code to shift by 63 
> instead, which allows to remove an UNSPEC and insn previously dedicated to this 
> case.
> 
> Cross-tested on aarch64-none-elf and aarch64_be-none-elf, with test coverage 
> provided by gcc.target/aarch64/sshr64_1.c .
> 
> gcc/ChangeLog:
> 
> 	* config/aarch64/aarch64.md (enum "unspec"): Remove UNSPEC_SSHR64.
> 
> 	* config/aarch64/aarch64-simd.md (aarch64_ashr_simddi): Change shift
> 	amount to 63 if was 64.
> 	(aarch64_sshr_simddi): Remove.
> 
> 
> 
> 
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