[BFD][AARCH64]Fix MOVW_SABS_G(0,1,2) relocation overflow check.

[Renlin Li]

Hi all,

This patch fixes the overflow check for
R_AARCH64_MOVW_SABS_G0
R_AARCH64_MOVW_SABS_G1
R_AARCH64_MOVW_SABS_G2

According to the aarch64 elf specification, for those relocations with 
overflow check, the following rule applies:

X > 0: Set the instruction to MOVZ and its immediate value to the 
selected bits S;
for relocation R_..._Gn, check that X< {G0: 2^16 , G1 : 2^32 , G2 : 2^48 
} (no check for R_..._G3).

X < 0: Set the instruction to MOVN and its immediate value to NOT 
(selected bits of);
for relocation R_..._Gn , check that -{ G0 : 2^16 , G1 : 2^32 , G2 : 
2^48 } ? X (no check for R_..._G3).

This rule indicates:
1, signed overflow check should be used.
2, For the allowed range, 17 bit signed value should be used, instead of 
16 bit.

Here the bitsize field is changed from 16 to 17, this field in aarch64 
backend is used for overflow check only.

the BFD already have the functions to re-encode the instruction into 
movz/movn according to the sign of the value.
Only the overflow check needs to be fixed!


binutils regression test checked Okay, Okay for trunk?

Regards,
Renlin Li



bfd/ChangeLog:

2016-02-25  Renlin Li  <renlin.li@arm.com>

     * elfnn-aarch64.c (elfNN_aarch64_howto_table): Fix signed overflow
     check for MOVW_SABS_G0, MOVW_SABS_G1, MOVW_SABS_G2.


ld/ChangeLog:

2016-02-25  Renlin Li  <renlin.li@arm.com>

     * testsuite/ld-aarch64/aarch64-elf.exp: Run new testcases.
     * testsuite/ld-aarch64/emit-relocs-270.d: Update to use new boundary.
     * testsuite/ld-aarch64/emit-relocs-271.d: Likewise.
     * testsuite/ld-aarch64/emit-relocs-272.d: Likewise.
     * testsuite/ld-aarch64/emit-relocs-270-overflow.d: New.
     * testsuite/ld-aarch64/emit-relocs-270-overflow.s: New.
     * testsuite/ld-aarch64/emit-relocs-271-overflow.d: New.
     * testsuite/ld-aarch64/emit-relocs-271-overflow.s: New.
     * testsuite/ld-aarch64/emit-relocs-272-overflow.d: New.
     * testsuite/ld-aarch64/emit-relocs-272-overflow.s: New.
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