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Re: RFC: Using DW_EH_PE_sdata* when converting absolute encodings to PC-relative form
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: binutils at sourceware dot org
- Date: Mon, 21 Sep 2009 20:08:37 +0100
- Subject: Re: RFC: Using DW_EH_PE_sdata* when converting absolute encodings to PC-relative form
- References: <87eiq16g0j.fsf@firetop.home> <4AB7955B.6020809@redhat.com>
Richard Henderson <rth@redhat.com> writes:
> On 09/20/2009 05:56 AM, Richard Sandiford wrote:
>> I was wondering
>> whether it was worth changing (a) to use an explicit signed
>> encoding, like most GCC ports do from the beginning.
>> I.e. whether the patch below was an improvement or not?
>> I realise it shouldn't matter in practice, but which is
>> theoretically better?
>
> I think it's better.
>
> Patch is ok.
Thanks. I installed the following too, to update it for the
personality stuff I added on Saturday.
Richard
bfd/
* elf-eh-frame.c (_bfd_elf_write_section_eh_frame): Extend previous
patch to handle the new personality relaxation.
ld/testsuite/
* ld-mips-elf/eh-frame5.d: Expect PC-relative encodings
to include DW_EH_PE_sdata4.
Index: bfd/elf-eh-frame.c
===================================================================
--- bfd/elf-eh-frame.c 2009-09-21 20:05:43.000000000 +0100
+++ bfd/elf-eh-frame.c 2009-09-21 20:06:13.000000000 +0100
@@ -1494,7 +1494,7 @@ _bfd_elf_write_section_eh_frame (bfd *ab
break;
case 'P':
if (ent->u.cie.make_per_encoding_relative)
- *buf |= DW_EH_PE_pcrel;
+ *buf = make_pc_relative (*buf, ptr_size);
per_encoding = *buf++;
per_width = get_DW_EH_PE_width (per_encoding, ptr_size);
BFD_ASSERT (per_width != 0);
Index: ld/testsuite/ld-mips-elf/eh-frame5.d
===================================================================
--- ld/testsuite/ld-mips-elf/eh-frame5.d 2009-09-21 20:05:43.000000000 +0100
+++ ld/testsuite/ld-mips-elf/eh-frame5.d 2009-09-21 20:06:13.000000000 +0100
@@ -46,12 +46,12 @@ Contents of the \.eh_frame section:
Data alignment factor: -4
Return address column: 31
#
-# 0xc12: DW_EH_PE_pcrel for personality encoding
+# 0xc12: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for personality encoding
# 0xc13: 0x820 - 0xc13 (local_pers - .)
-# 0xc17: DW_EH_PE_pcrel for LDSA encoding
+# 0xc17: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xc18: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 10 ff ff fc 0d 10 1b
+ Augmentation data: 1b ff ff fc 0d 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -76,12 +76,12 @@ Contents of the \.eh_frame section:
Data alignment factor: -4
Return address column: 31
#
-# 0xc46: DW_EH_PE_pcrel for personality encoding
+# 0xc46: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for personality encoding
# 0xc47: 0x824 - 0xc47 (hidden_pers - .)
-# 0xc4d: DW_EH_PE_pcrel for LDSA encoding
+# 0xc4d: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xc4e: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 10 ff ff fb dd 10 1b
+ Augmentation data: 1b ff ff fb dd 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -108,10 +108,10 @@ Contents of the \.eh_frame section:
#
# 0xc7a: DW_EH_PE_absptr for personality encoding
# 0xc7b: global_pers (reloc above)
-# 0xc7f: DW_EH_PE_pcrel for LDSA encoding
+# 0xc7f: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xc80: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 00 00 00 00 00 10 1b
+ Augmentation data: 00 00 00 00 00 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -138,10 +138,10 @@ Contents of the \.eh_frame section:
#
# 0xcae: DW_EH_PE_absptr for personality encoding
# 0xcaf: extern_pers (reloc above)
-# 0xcb3: DW_EH_PE_pcrel for LDSA encoding
+# 0xcb3: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xcb4: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 00 00 00 00 00 10 1b
+ Augmentation data: 00 00 00 00 00 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -166,12 +166,13 @@ Contents of the \.eh_frame section:
Data alignment factor: -4
Return address column: 31
#
-# 0xce2: DW_EH_PE_indirect | DW_EH_PE_pcrel for personality encoding
+# 0xce2: DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4
+# for personality encoding
# 0xce3: 0x10000 - 0xce3 (local_indirect_ptr - .)
-# 0xce7: DW_EH_PE_pcrel for LDSA encoding
+# 0xce7: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xce8: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 90 00 00 f3 1d 10 1b
+ Augmentation data: 9b 00 00 f3 1d 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -196,12 +197,12 @@ Contents of the \.eh_frame section:
Data alignment factor: -4
Return address column: 31
#
-# 0xd16: DW_EH_PE_pcrel for personality encoding
+# 0xd16: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for personality encoding
# 0xd17: 0x10004 - 0xd17 (hidden_indirect_ptr - .)
-# 0xd1d: DW_EH_PE_pcrel for LDSA encoding
+# 0xd1d: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xd1e: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 90 00 00 f2 ed 10 1b
+ Augmentation data: 9b 00 00 f2 ed 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -228,10 +229,10 @@ Contents of the \.eh_frame section:
#
# 0xd4a: DW_EH_PE_indirect | DW_EH_PE_absptr for personality encoding
# 0xd4b: global_indirect_ptr (reloc above)
-# 0xd4f: DW_EH_PE_pcrel for LDSA encoding
+# 0xd4f: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xd50: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 80 00 00 00 00 10 1b
+ Augmentation data: 80 00 00 00 00 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop
@@ -258,10 +259,10 @@ Contents of the \.eh_frame section:
#
# 0xd7e: DW_EH_PE_indirect | DW_EH_PE_absptr for personality encoding
# 0xd7f: extern_indirect_ptr (reloc above)
-# 0xd83: DW_EH_PE_pcrel for LDSA encoding
+# 0xd83: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for LDSA encoding
# 0xd84: DW_EH_PE_pcrel | DW_EH_PE_sdata4 for FDE encoding
#
- Augmentation data: 80 00 00 00 00 10 1b
+ Augmentation data: 80 00 00 00 00 1b 1b
DW_CFA_def_cfa_register: r29
DW_CFA_nop