aboutsummaryrefslogtreecommitdiff
path: root/bfd
diff options
context:
space:
mode:
authorPalmer Dabbelt <palmer@dabbelt.com>2017-05-18 18:08:25 -0700
committerPalmer Dabbelt <palmer@dabbelt.com>2017-10-19 09:19:32 -0700
commitff6f4d9b2d6c25ac144bab869df6e3d6123a6f8f (patch)
tree59e6a3f173dd8987b985d830a745f06e6b881f9d /bfd
parent95e42ad4425f0ab0ebfb90035a891be576f9fca4 (diff)
downloadgdb-ff6f4d9b2d6c25ac144bab869df6e3d6123a6f8f.zip
gdb-ff6f4d9b2d6c25ac144bab869df6e3d6123a6f8f.tar.gz
gdb-ff6f4d9b2d6c25ac144bab869df6e3d6123a6f8f.tar.bz2
RISC-V: Add R_RISCV_DELETE, which marks bytes for deletion
We currently delete bytes by shifting an entire BFD backwards to overwrite the bytes we no longer need. The result is that relaxing a BFD is quadratic time. This patch adds an additional relocation that specifies a byte range that will be deleted from the final object file, and adds a relaxation pass (between the existing passes that delete bytes and the alignment pass) that actually deletes the bytes. Note that deletion is still quadratic time, and nothing uses R_RISCV_DELETE yet. I've been meaning to go convert all the other relaxations to use R_RISCV_DELETE and then make it faster, but this patch has been sitting around for months so it looks like that won't happen for a bit. The PCREL->GPREL relaxation that comes next uses this, and since we've been using these two patches out of tree since I wrote them months ago I figure it's better to just get them in now. I (or someone else :)) can convert all the relocations later... R_RISCV_DELETE will never be emitted into ELF objects, so therefor isn't exposed to the rest of binutils. As such, we're not considering this as part of the ABI. bfd/ChangeLog 2017-10-19 Palmer Dabbelt <palmer@dabbelt.com> * elfnn-riscv (R_RISCV_DELETE): New define. (_bfd_riscv_relax_delete): New function. (perform_relocation): Handle R_RISCV_DELETE. (_bfd_riscv_relax_section): Likewise. ld/ChangeLog 2017-10-19 Palmer Dabbelt <palmer@dabbelt.com> * emultempl/riscvelf.em (riscv_elf_before_allocation): Add a third relaxation pass.
Diffstat (limited to 'bfd')
-rw-r--r--bfd/ChangeLog7
-rw-r--r--bfd/elfnn-riscv.c36
2 files changed, 40 insertions, 3 deletions
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 959cf06..772f526 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2017-10-19 Palmer Dabbelt <palmer@dabbelt.com>
+
+ * elfnn-riscv.c (R_RISCV_DELETE): New define.
+ (_bfd_riscv_relax_delete): New function.
+ (perform_relocation): Handle R_RISCV_DELETE.
+ (_bfd_riscv_relax_section): Likewise.
+
2017-10-19 H.J. Lu <hongjiu.lu@intel.com>
PR ld/22263
diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index d28cabd..bd88ed7 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -32,6 +32,9 @@
#include "elf/riscv.h"
#include "opcode/riscv.h"
+/* Internal relocations used exclusively by the relaxation pass. */
+#define R_RISCV_DELETE (R_RISCV_max + 1)
+
#define ARCH_SIZE NN
#define MINUS_ONE ((bfd_vma)0 - 1)
@@ -1483,6 +1486,9 @@ perform_relocation (const reloc_howto_type *howto,
case R_RISCV_TLS_DTPREL64:
break;
+ case R_RISCV_DELETE:
+ return bfd_reloc_ok;
+
default:
return bfd_reloc_notsupported;
}
@@ -1805,6 +1811,7 @@ riscv_elf_relocate_section (bfd *output_bfd,
case R_RISCV_SET16:
case R_RISCV_SET32:
case R_RISCV_32_PCREL:
+ case R_RISCV_DELETE:
/* These require no special handling beyond perform_relocation. */
break;
@@ -2947,8 +2954,28 @@ _bfd_riscv_relax_align (bfd *abfd, asection *sec,
rel->r_addend - nop_bytes);
}
-/* Relax a section. Pass 0 shortens code sequences unless disabled.
- Pass 1, which cannot be disabled, handles code alignment directives. */
+/* Relax PC-relative references to GP-relative references. */
+
+static bfd_boolean
+_bfd_riscv_relax_delete (bfd *abfd,
+ asection *sec,
+ asection *sym_sec ATTRIBUTE_UNUSED,
+ struct bfd_link_info *link_info ATTRIBUTE_UNUSED,
+ Elf_Internal_Rela *rel,
+ bfd_vma symval ATTRIBUTE_UNUSED,
+ bfd_vma max_alignment ATTRIBUTE_UNUSED,
+ bfd_vma reserve_size ATTRIBUTE_UNUSED,
+ bfd_boolean *again ATTRIBUTE_UNUSED)
+{
+ if (!riscv_relax_delete_bytes(abfd, sec, rel->r_offset, rel->r_addend))
+ return FALSE;
+ rel->r_info = ELFNN_R_INFO(0, R_RISCV_NONE);
+ return TRUE;
+}
+
+/* Relax a section. Pass 0 shortens code sequences unless disabled. Pass 1
+ deletes the bytes that pass 0 made obselete. Pass 2, which cannot be
+ disabled, handles code alignment directives. */
static bfd_boolean
_bfd_riscv_relax_section (bfd *abfd, asection *sec,
@@ -3001,6 +3028,7 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
int type = ELFNN_R_TYPE (rel->r_info);
bfd_vma symval;
+ relax_func = NULL;
if (info->relax_pass == 0)
{
if (type == R_RISCV_CALL || type == R_RISCV_CALL_PLT)
@@ -3026,7 +3054,9 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
/* Skip over the R_RISCV_RELAX. */
i++;
}
- else if (type == R_RISCV_ALIGN)
+ else if (info->relax_pass == 1 && type == R_RISCV_DELETE)
+ relax_func = _bfd_riscv_relax_delete;
+ else if (info->relax_pass == 2 && type == R_RISCV_ALIGN)
relax_func = _bfd_riscv_relax_align;
else
continue;