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RISC-V: adjust logic to avoid register name symbols
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Special casing GPR names in my_getSmallExpression() leads to a number of
inconsistencies. Generalize this by utilizing the md_parse_name() hook,
limited to when instruction operands are being parsed (really: probed).
Then both the GPR lookup there and the yet more ad hoc workaround for
PR/gas 29940 can be removed (including its extension needed for making
the compressed form JAL work again).
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@jbeulich @ouuleilei-bot
jbeulich authored and ouuleilei-bot committed Mar 10, 2023
1 parent e20d415 commit f99d279
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Showing 2 changed files with 98 additions and 27 deletions.
121 changes: 94 additions & 27 deletions gas/config/tc-riscv.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,8 @@ static enum float_abi float_abi = FLOAT_ABI_DEFAULT;

static unsigned elf_flags = 0;

static bool probing_insn_operands;

/* Set the default_isa_spec. Return 0 if the spec isn't supported.
Otherwise, return 1. */

Expand Down Expand Up @@ -2228,21 +2230,10 @@ my_getSmallExpression (expressionS *ep, bfd_reloc_code_real_type *reloc,
char *str, const struct percent_op_match *percent_op)
{
size_t reloc_index;
unsigned crux_depth, str_depth, regno;
unsigned crux_depth, str_depth;
bool orig_probing = probing_insn_operands;
char *crux;

/* First, check for integer registers. No callers can accept a reg, but
we need to avoid accidentally creating a useless undefined symbol below,
if this is an instruction pattern that can't match. A glibc build fails
if this is removed. */
if (reg_lookup (&str, RCLASS_GPR, &regno))
{
ep->X_op = O_register;
ep->X_add_number = regno;
expr_parse_end = str;
return 0;
}

/* Search for the start of the main expression.
End the loop with CRUX pointing to the start of the main expression and
Expand Down Expand Up @@ -2274,9 +2265,17 @@ my_getSmallExpression (expressionS *ep, bfd_reloc_code_real_type *reloc,
return 0;
}

/* Anything inside parentheses or subject to a relocation operator cannot
be a register and hence can be treated the same as operands to
directives (other than .insn). */
if (str_depth || reloc_index)
probing_insn_operands = false;

my_getExpression (ep, crux);
str = expr_parse_end;

probing_insn_operands = orig_probing;

/* Match every open bracket. */
while (crux_depth > 0 && (*str == ')' || *str == ' ' || *str == '\t'))
if (*str++ == ')')
Expand Down Expand Up @@ -2462,6 +2461,13 @@ riscv_is_priv_insn (insn_t insn)
|| ((insn ^ MATCH_SFENCE_VM) & MASK_SFENCE_VM) == 0);
}

static symbolS *deferred_sym_rootP;
static symbolS *deferred_sym_lastP;
/* Since symbols can't easily be freed, try to recycle ones which weren't
committed. */
static symbolS *orphan_sym_rootP;
static symbolS *orphan_sym_lastP;

/* This routine assembles an instruction into its binary format. As a
side effect, it sets the global variable imm_reloc to the type of
relocation to do if one of the operands is an address expression. */
Expand Down Expand Up @@ -2497,6 +2503,8 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,

insn = (struct riscv_opcode *) str_hash_find (hash, str);

probing_insn_operands = true;

asargStart = asarg;
for ( ; insn && insn->name && strcmp (insn->name, str) == 0; insn++)
{
Expand All @@ -2513,6 +2521,17 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
/* Reset error message of the previous round. */
error.msg = _("illegal operands");
error.missing_ext = NULL;

/* Purge deferred symbols from the previous round, if any. */
while (deferred_sym_rootP)
{
symbolS *sym = deferred_sym_rootP;

symbol_remove (sym, &deferred_sym_rootP, &deferred_sym_lastP);
symbol_append (sym, orphan_sym_lastP, &orphan_sym_rootP,
&orphan_sym_lastP);
}

create_insn (ip, insn);

imm_expr->X_op = O_absent;
Expand Down Expand Up @@ -2567,9 +2586,22 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
}
if (*asarg != '\0')
break;

/* Successful assembly. */
error.msg = NULL;
insn_with_csr = false;

/* Commit deferred symbols, if any. */
while (deferred_sym_rootP)
{
symbolS *sym = deferred_sym_rootP;

symbol_remove (sym, &deferred_sym_rootP,
&deferred_sym_lastP);
symbol_append (sym, symbol_lastP, &symbol_rootP,
&symbol_lastP);
symbol_table_insert (sym);
}
goto out;

case 'C': /* RVC */
Expand Down Expand Up @@ -2773,8 +2805,6 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
case 'p':
goto branch;
case 'a':
if (oparg == insn->args + 1)
goto jump_check_gpr;
goto jump;
case 'S': /* Floating-point RS1 x8-x15. */
if (!reg_lookup (&asarg, RCLASS_FPR, &regno)
Expand Down Expand Up @@ -3278,18 +3308,6 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
continue;

case 'a': /* 20-bit PC-relative offset. */
/* Like in my_getSmallExpression() we need to avoid emitting
a stray undefined symbol if the 1st JAL entry doesn't match,
but the 2nd (with 2 operands) might. */
if (oparg == insn->args)
{
jump_check_gpr:
asargStart = asarg;
if (reg_lookup (&asarg, RCLASS_GPR, NULL)
&& (*asarg == ',' || (ISSPACE (*asarg) && asarg[1] == ',')))
break;
asarg = asargStart;
}
jump:
my_getExpression (imm_expr, asarg);
asarg = expr_parse_end;
Expand Down Expand Up @@ -3512,6 +3530,8 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
if (save_c)
*(asargStart - 1) = save_c;

probing_insn_operands = false;

return error;
}

Expand Down Expand Up @@ -3808,6 +3828,53 @@ riscv_after_parse_args (void)
flag_dwarf_cie_version = 3;
}

bool riscv_parse_name (const char *name, struct expressionS *ep,
enum expr_mode mode)
{
unsigned int regno;
symbolS *sym;

if (!probing_insn_operands)
return false;

gas_assert (mode == expr_normal);

regno = reg_lookup_internal (name, RCLASS_GPR);
if (regno == (unsigned int)-1)
return false;

if (symbol_find (name) != NULL)
return false;

/* Create a symbol without adding it to the symbol table yet.
Insertion will happen only once we commit to using the insn
we're probing operands for. */
for (sym = deferred_sym_rootP; sym; sym = symbol_next (sym))
if (strcmp (name, S_GET_NAME (sym)) == 0)
break;
if (!sym)
{
for (sym = orphan_sym_rootP; sym; sym = symbol_next (sym))
if (strcmp (name, S_GET_NAME (sym)) == 0)
{
symbol_remove (sym, &orphan_sym_rootP, &orphan_sym_lastP);
break;
}
if (!sym)
sym = symbol_create (name, undefined_section,
&zero_address_frag, 0);

symbol_append (sym, deferred_sym_lastP, &deferred_sym_rootP,
&deferred_sym_lastP);
}

ep->X_op = O_symbol;
ep->X_add_symbol = sym;
ep->X_add_number = 0;

return true;
}

long
md_pcrel_from (fixS *fixP)
{
Expand Down
4 changes: 4 additions & 0 deletions gas/config/tc-riscv.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,10 @@ extern void riscv_elf_final_processing (void);
/* Adjust debug_line after relaxation. */
#define DWARF2_USE_FIXED_ADVANCE_PC 1

#define md_parse_name(name, exp, mode, c) \
riscv_parse_name (name, exp, mode)
bool riscv_parse_name (const char *, struct expressionS *, enum expr_mode);

#define md_finish riscv_md_finish
#define CONVERT_SYMBOLIC_ATTRIBUTE riscv_convert_symbolic_attribute

Expand Down

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