[Bug target/79041] aarch64 backend emits R_AARCH64_ADR_PREL_PG_HI21 relocation despite -mpc-relative-literal-loads option being used

["wilco at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79041

--- Comment #15 from Wilco <wilco at gcc dot gnu.org> ---
Author: wilco
Date: Wed Jan 17 16:31:42 2018
New Revision: 256800

URL: https://gcc.gnu.org/viewcvs?rev=256800&root=gcc&view=rev
Log:
[AArch64] PR82964: Fix 128-bit immediate ICEs

This fixes PR82964 which reports ICEs for some CONST_WIDE_INT immediates.
It turns out decimal floating point CONST_DOUBLE get changed into
CONST_WIDE_INT without checking the constraint on the operand, which 
results in failures.  Avoid this by only allowing SF/DF/TF mode floating
point constants in aarch64_legitimate_constant_p.  A similar issue can
occur with 128-bit immediates which may be emitted even when disallowed
in aarch64_legitimate_constant_p, and the constraints in movti_aarch64
don't match.  Fix this with a new constraint and allowing valid immediates
in aarch64_legitimate_constant_p.

Rather than allowing all 128-bit immediates and expanding in up to 8
MOV/MOVK instructions, limit them to 4 instructions and use a literal
load for other cases.  Improve a few TImode tests to use a literal and
ensure they are skipped with -fpic.

This fixes all reported failures.

    gcc/
        PR target/82964
        * config/aarch64/aarch64.md (movti_aarch64): Use Uti constraint.
        * config/aarch64/aarch64.c (aarch64_mov128_immediate): New function.
        (aarch64_legitimate_constant_p): Just support CONST_DOUBLE 
        SF/DF/TF mode to avoid creating illegal CONST_WIDE_INT immediates.
        * config/aarch64/aarch64-protos.h (aarch64_mov128_immediate):
        Add declaration.
        * config/aarch64/constraints.md (aarch64_movti_operand):
        Limit immediates.
        * config/aarch64/predicates.md (Uti): Add new constraint.

    gcc/testsuite/
        PR target/79041
        PR target/82964
        * gcc.target/aarch64/pr79041-2.c: Improve test, disable with fpic.
        * gcc.target/aarch64/pr78733.c: Improve test, disable with fpic.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/aarch64/aarch64-protos.h
    trunk/gcc/config/aarch64/aarch64.c
    trunk/gcc/config/aarch64/aarch64.md
    trunk/gcc/config/aarch64/constraints.md
    trunk/gcc/config/aarch64/predicates.md
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.target/aarch64/pr78733.c
    trunk/gcc/testsuite/gcc.target/aarch64/pr79041-2.c