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added ie to le relaxation #7

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125 changes: 120 additions & 5 deletions bfd/elfnn-riscv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4690,6 +4690,96 @@ _bfd_riscv_relax_lui (bfd *abfd,
return true;
}

/*

summary
0000000000000000 <some_label>:
0: 00000517 auipc a0,0x0
4: 00053503 ld a0,0(a0) # 0 <o_start>
8: 9512 add a0,a0,tp
a: 4108 lw a0,0(a0)
c: 8082 ret

Relocation section '.rela.text' at offset 0x1d8 contains 3 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000000 000700000015 R_RISCV_TLS_GOT_H20 0000000000000000 ThreadVar + 0
000000000004 000200000018 R_RISCV_PCREL_LO12_I 0000000000000000 .Lpcrel_hi0 + 0
000000000004 000000000033 R_RISCV_RELAX 0

the goal is to convert auipc to lui and attach R_RISCV_TPREL_HI20
and delete instruction assosiated with R_RISCV_PCREL_LO12_I {ld,lw}
so that it mirrors relocations for le

after this relaxation
0000000000000000 <some_label>:
0: 00000517 lui a0,0x0
8: 9512 add a0,a0,tp
a: 4108 lw a0,0(a0)
c: 8082 ret

the add and lw/ld after lui need to have tprel add and tprel_lo12i relocation which need to be emitted by compiler

the lui add and lw to be taken care by _bfd_riscv_relax_tls_le

*/
static bool
_bfd_riscv_relax_tls_ie_to_le (bfd *abfd,
asection *sec,
asection *sym_sec ATTRIBUTE_UNUSED,
struct bfd_link_info *link_info,
Elf_Internal_Rela *rel,
bfd_vma symval,
bfd_vma max_alignment ATTRIBUTE_UNUSED,
bfd_vma reserve_size ATTRIBUTE_UNUSED,
bool *again,
riscv_pcgp_relocs *pcgp_relocs,
bool undefined_weak ATTRIBUTE_UNUSED)
{
bfd_byte *contents = elf_section_data (sec)->this_hdr.contents;
bool ret = false;
if (RISCV_CONST_HIGH_PART (tpoff (link_info, symval)) != 0)
return true;

BFD_ASSERT (rel->r_offset + 4 <= sec->size);
chek:
switch (ELFNN_R_TYPE (rel->r_info))
{
//_RISCV_TLS_GOT_HI20 relaxation
case R_RISCV_TLS_GOT_HI20:
//here we do converion from auipc -> lui because both are utype instructions
//attach R_RISCV_TPREL_HI20 relocation
if(VALID_UTYPE_IMM (RISCV_CONST_HIGH_PART (symval) ))
{
*again = true;
bfd_vma tolui = bfd_getl32(contents + rel->r_offset);
tolui = (tolui & ~MASK_AUIPC) | MATCH_LUI;
bfd_putl32 (tolui , contents + rel->r_offset);
rel->r_info = ELFNN_R_INFO (ELFNN_R_SYM (rel->r_info) , R_RISCV_TPREL_HI20);
rel = rel + 1;
goto chek;
}
else
{
abort();
}
break;
//delete the lo12 assosiated with previous hi20 as its no longer required
case R_RISCV_PCREL_LO12_I:
*again = true;
ret = riscv_relax_delete_bytes (abfd, sec, rel->r_offset, 4, link_info,
pcgp_relocs, rel);
break;
case R_RISCV_PCREL_LO12_S:
*again = true;
ret = riscv_relax_delete_bytes (abfd, sec, rel->r_offset, 4, link_info,
pcgp_relocs, rel);
break;
default:
abort ();
}
return ret;

}
/* Relax non-PIC TLS references to TP-relative references. */

static bool
Expand Down Expand Up @@ -4965,7 +5055,7 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
bfd_vma max_alignment, reserve_size = 0;
riscv_pcgp_relocs pcgp_relocs;
static asection *first_section = NULL;

bool skip_reloc = false;
*again = false;

if (bfd_link_relocatable (info)
Expand Down Expand Up @@ -5015,7 +5105,6 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
bfd_vma symval;
char symtype;
bool undefined_weak = false;

relax_func = NULL;
riscv_relax_delete_bytes = NULL;
if (info->relax_pass == 0)
Expand All @@ -5027,6 +5116,8 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
|| type == R_RISCV_LO12_I
|| type == R_RISCV_LO12_S)
relax_func = _bfd_riscv_relax_lui;
else if (type == R_RISCV_TLS_GOT_HI20)
relax_func = _bfd_riscv_relax_tls_ie_to_le;
else if (type == R_RISCV_TPREL_HI20
|| type == R_RISCV_TPREL_ADD
|| type == R_RISCV_TPREL_LO12_I
Expand All @@ -5042,7 +5133,8 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
riscv_relax_delete_bytes = _riscv_relax_delete_piecewise;

/* Only relax this reloc if it is paired with R_RISCV_RELAX. */
if (i == sec->reloc_count - 1
if(type == R_RISCV_TLS_GOT_HI20){}
else if(i == sec->reloc_count - 1
|| ELFNN_R_TYPE ((rel + 1)->r_info) != R_RISCV_RELAX
|| rel->r_offset != (rel + 1)->r_offset)
continue;
Expand Down Expand Up @@ -5114,7 +5206,6 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,

indx = ELFNN_R_SYM (rel->r_info) - symtab_hdr->sh_info;
h = elf_sym_hashes (abfd)[indx];

while (h->root.type == bfd_link_hash_indirect
|| h->root.type == bfd_link_hash_warning)
h = (struct elf_link_hash_entry *) h->root.u.i.link;
Expand Down Expand Up @@ -5142,7 +5233,31 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
need the more rigorous checking for this optimization. */
undefined_weak = true;
}

/* conditions to check ie -> le relaxation */
if (relax_func == _bfd_riscv_relax_tls_ie_to_le )
{
bool need_reloc = false;
int ind=0;
bool dyn = htab->elf.dynamic_sections_created;
RISCV_TLS_GD_IE_NEED_DYN_RELOC(info, dyn, h, ind, need_reloc);
/* dont relax ie -> le if the relocation requires us to make dynamic relocations or when there are weak definitions or when we are not creating exec*/
if(need_reloc || h->root.type == bfd_link_hash_undefweak || h->root.type == bfd_link_hash_defweak || !(bfd_link_executable (info)) )
{
skip_reloc = true;
continue;
}
/* skip relocs of TPREL_ADD TPREL_LO12_ I/S and PCREL_LO12_ I/S
assuming that compiler emits these relocs for ie and
first occurence of these relocs after TLS_GOT_HI20 is related to ie*/
}
if(skip_reloc && (relax_func == _bfd_riscv_relax_pc
|| relax_func == _bfd_riscv_relax_tls_le))
{
/* reset skip_reloc on final inst related to ie*/
if(type == R_RISCV_TPREL_LO12_I || type == R_RISCV_TPREL_LO12_S)
skip_reloc = false;
continue;
}
/* This line has to match the check in riscv_elf_relocate_section
in the R_RISCV_CALL[_PLT] case. */
if (bfd_link_pic (info) && h->plt.offset != MINUS_ONE)
Expand Down