... and use address spaces to load boundary value from TLS block.

The patch removes special handling for boundary value location.

2017-08-10  Uros Bizjak  <ubizjak@gmail.com>

    * config/i386/i386-protos.h (ix86_split_stack_boundary): New prototype.
    * config/i386/i386.c (ix86_split_stack_boundary): New function.
    (ix86_xpand_split_stack_prologue): Call ix86_split_stack_boundary.
    (ix86_legitimate_address_p) <case UNSPEC_STACK_CHECK>: Remove.
    (i386_asm_output_addr_const_extra) <case UNSPEC_STACK_CHECK>: Ditto.
    (optput_pic_addr_const): Remove UNSPEC_STACK_CHECK handling.
    * config/i386/i386.md (unspec): Remove UNSPEC_STACK_CHECK.
    (split_stack_space_check): Call ix86_split_stack_boundary.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32} with
all default languages plus go.

Committed to mainline SVN.

Uros.