PowerPC addpcis fix

This came up because I was looking at ld/tmpdir/addpcis.o and noticed
the odd addends on REL16DX_HA.  They ought to both be -4.  The error
crept in due REL16DX_HA howto being pc-relative (as indeed it should
be), and code at gas/write.c:1001 after this comment
	      /* Make it pc-relative.  If the back-end code has not
		 selected a pc-relative reloc, cancel the adjustment
		 we do later on all pc-relative relocs.  */
*not* cancelling the pc-relative adjustment.  So I've made a dummy
non-relative split reloc so that the generic code handles this, rather
than attempting to add hacks later in md_apply_fix which would not be
very robust.  Having the new internal reloc also makes it easy to
support

 addpcis rx,sym@ha

as an equivalent to

 addpcis rx,(sym-0f)@ha
0:

The patch also fixes overflow checking, which must test whether the
addi will overflow too since @l relocs don't have any overflow check.

Lastly, since I was poking at md_apply_fix, I arranged to have the
generic gas/write.c code emit errors for subtraction expressions where
we lack reloc support.

include/
	* elf/ppc64.h (R_PPC64_16DX_HA): New.  Expand fake reloc comment.
	* elf/ppc.h (R_PPC_16DX_HA): Likewise.
bfd/
	* reloc.c (BFD_RELOC_PPC_16DX_HA): New.
	* elf64-ppc.c (ppc64_elf_howto_raw <R_PPC64_16DX_HA>): New howto.
	(ppc64_elf_reloc_type_lookup): Translate new bfd reloc.
	(ppc64_elf_ha_reloc): Correct overflow test on REL16DX_HA.
	(ppc64_elf_relocate_section): Likewise.
	* elf32-ppc.c (ppc_elf_howto_raw <R_PPC_16DX_HA>): New howto.
	(ppc_elf_reloc_type_lookup): Translate new bfd reloc.
	(ppc_elf_check_relocs): Handle R_PPC_16DX_HA to pacify gcc.
	* libbfd.h: Regenerate.
	* bfd-in2.h: Regenerate.
gas/
	* config/tc-ppc.c (md_assemble): Use BFD_RELOC_PPC_16DX_HA for addpcis.
	(md_apply_fix): Remove fx_subsy check.  Move code converting to
	pcrel reloc earlier and handle BFD_RELOC_PPC_16DX_HA.  Remove code
	emiiting errors on seeing fx_pcrel set on unexpected relocs, as
	that is done now by the generic code via..
	* config/tc-ppc.h (TC_FORCE_RELOCATION_SUB_LOCAL): ..this. Define.
	(TC_VALIDATE_FIX_SUB): Define.
ld/
	* testsuite/ld-powerpc/addpcis.d: Define ext1 and ext2 at
	limits of addpcis range.

2 files changed, 9 insertions, 4 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index ceee695..99be366 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,8 @@
+2017-02-28  Alan Modra  <amodra@gmail.com>
+
+	* testsuite/ld-powerpc/addpcis.d: Define ext1 and ext2 at
+	limits of addpcis range.
+
 2017-02-28  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* testsuite/ld-mips-elf/jalr4.dd: Adjust for `jalr $0, $25'
diff --git a/ld/testsuite/ld-powerpc/addpcis.d b/ld/testsuite/ld-powerpc/addpcis.d
index c0e2679..b150ca4 100644
--- a/ld/testsuite/ld-powerpc/addpcis.d
+++ b/ld/testsuite/ld-powerpc/addpcis.d
@@ -1,6 +1,6 @@
 #source: addpcis.s
 #as: -a64 -mpower9
-#ld: -melf64ppc -Ttext=0x10000000 --defsym ext1=0 --defsym ext2=0x8fff0000
+#ld: -melf64ppc -Ttext=0x10000000 --defsym ext1=-0x70007ffc --defsym ext2=0x8fff800b
 #objdump: -d -Mpower9
 
 .*:     file format .*
@@ -8,10 +8,10 @@
 Disassembly of section \.text:
 
 0+10000000 <_start>:
-    10000000:	(4c 60 f0 04|04 f0 60 4c) 	addpcis r3,-4096
-    10000004:	(38 63 ff fc|fc ff 63 38) 	addi    r3,r3,-4
+    10000000:	(4c 60 80 04|04 80 60 4c) 	addpcis r3,-32768
+    10000004:	(38 63 80 00|00 80 63 38) 	addi    r3,r3,-32768
     10000008:	(4c 9f 7f c5|c5 7f 9f 4c) 	addpcis r4,32767
-    1000000c:	(38 84 ff f4|f4 ff 84 38) 	addi    r4,r4,-12
+    1000000c:	(38 84 7f ff|ff 7f 84 38) 	addi    r4,r4,32767
     10000010:	(4c a0 00 05|05 00 a0 4c) 	addpcis r5,1
     10000014:	(38 a5 80 00|00 80 a5 38) 	addi    r5,r5,-32768
 	\.\.\.