From a217f122fa8df064aa0766be7a289174ab49b840 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Mon, 13 Sep 1999 03:44:49 +0000 Subject: [PATCH] Tidy jump handling code and comments. --- gas/config/tc-i386.c | 110 ++++++++++++++++++++++++++----------------- 1 file changed, 66 insertions(+), 44 deletions(-) diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c index c2d894ba349..197387aaadb 100644 --- a/gas/config/tc-i386.c +++ b/gas/config/tc-i386.c @@ -236,8 +236,8 @@ static char stackop_size = '\0'; /* Used in 16 bit gcc mode to add an l /* Interface to relax_segment. There are 2 relax states for 386 jump insns: one for conditional & - one for unconditional jumps. This is because the these two types - of jumps add different sizes to frags when we're figuring out what + one for unconditional jumps. This is because these two types of + jumps add different sizes to frags when we're figuring out what sort of jump to choose to reach a given label. */ /* types */ @@ -2092,23 +2092,33 @@ md_assemble (line) /* Output jumps. */ if (i.tm.opcode_modifier & Jump) { - long n = (long) i.disps[0]->X_add_number; - int prefix = (i.prefix[DATA_PREFIX] != 0); - int code16 = 0; + int size; + int code16; + int prefix; - if (prefix) + code16 = 0; + if (flag_16bit_code) + code16 = CODE16; + + prefix = 0; + if (i.prefix[DATA_PREFIX]) { + prefix = 1; i.prefixes -= 1; - code16 = CODE16; + code16 ^= CODE16; } - if (flag_16bit_code) - code16 ^= CODE16; - if (!intel_syntax && (i.prefixes != 0)) + size = 4; + if (code16) + size = 2; + + if (i.prefixes != 0 && !intel_syntax) as_warn (_("skipping prefixes on this instruction")); if (i.disps[0]->X_op == O_constant) { + long n = (long) i.disps[0]->X_add_number; + if (fits_in_signed_byte (n)) { insn_size += 2; @@ -2122,7 +2132,6 @@ md_assemble (line) because text segments are limited to 64K anyway; Use 32-bit jumps for 32-bit code, because they're faster, and a 16-bit jump will clear the top 16 bits of %eip. */ - int jmp_size = code16 ? 2 : 4; if (code16 && !fits_in_signed_word (n)) { as_bad (_("16-bit jump out of range")); @@ -2132,56 +2141,60 @@ md_assemble (line) if (i.tm.base_opcode == JUMP_PC_RELATIVE) { /* pace */ /* unconditional jump */ - insn_size += prefix + 1 + jmp_size; - p = frag_more (prefix + 1 + jmp_size); + insn_size += prefix + 1 + size; + p = frag_more (prefix + 1 + size); if (prefix) *p++ = DATA_PREFIX_OPCODE; *p++ = (char) 0xe9; - md_number_to_chars (p, (valueT) n, jmp_size); + md_number_to_chars (p, (valueT) n, size); } else { /* conditional jump */ - insn_size += prefix + 2 + jmp_size; - p = frag_more (prefix + 2 + jmp_size); + insn_size += prefix + 2 + size; + p = frag_more (prefix + 2 + size); if (prefix) *p++ = DATA_PREFIX_OPCODE; *p++ = TWO_BYTE_OPCODE_ESCAPE; *p++ = i.tm.base_opcode + 0x10; - md_number_to_chars (p, (valueT) n, jmp_size); + md_number_to_chars (p, (valueT) n, size); } } } else { - int size = code16 ? 2 : 4; - - /* It's a symbol; end frag & setup for relax. - Make sure there are more than 6 chars left in the current frag; - if not we'll have to start a new one. */ - frag_grow (prefix + 1 + 2 + size); - insn_size += 1 + prefix; - p = frag_more (1 + prefix); + /* It's a symbol; End frag & setup for relax. + Make sure there is enough room in this frag for the largest + instruction we may generate in md_convert_frag. This is 2 + bytes for the opcode and room for the prefix and largest + displacement. */ + frag_grow (prefix + 2 + size); + insn_size += prefix + 1; + /* Prefix and 1 opcode byte go in fr_fix. */ + p = frag_more (prefix + 1); if (prefix) *p++ = DATA_PREFIX_OPCODE; *p = i.tm.base_opcode; + /* 1 possible extra opcode + displacement go in fr_var */ frag_var (rs_machine_dependent, - prefix + 2 + size, /* 2 opcode/prefix + displacement */ + 1 + size, 1, ((unsigned char) *p == JUMP_PC_RELATIVE ? ENCODE_RELAX_STATE (UNCOND_JUMP, SMALL) | code16 : ENCODE_RELAX_STATE (COND_JUMP, SMALL) | code16), i.disps[0]->X_add_symbol, - (offsetT) n, p); + i.disps[0]->X_add_number, + p); } } else if (i.tm.opcode_modifier & (JumpByte | JumpDword)) { - int size = (i.tm.opcode_modifier & JumpByte) ? 1 : 4; - long n = (long) i.disps[0]->X_add_number; + int size; - if (size == 1) /* then this is a loop or jecxz type instruction */ + if (i.tm.opcode_modifier & JumpByte) { + /* This is a loop or jecxz type instruction. */ + size = 1; if (i.prefix[ADDR_PREFIX]) { insn_size += 1; @@ -2191,23 +2204,26 @@ md_assemble (line) } else { - int code16 = 0; + int code16; + + code16 = 0; + if (flag_16bit_code) + code16 = CODE16; if (i.prefix[DATA_PREFIX]) { insn_size += 1; FRAG_APPEND_1_CHAR (DATA_PREFIX_OPCODE); i.prefixes -= 1; - code16 = CODE16; + code16 ^= CODE16; } - if (flag_16bit_code) - code16 ^= CODE16; + size = 4; if (code16) size = 2; } - if (!intel_syntax && (i.prefixes != 0)) + if (i.prefixes != 0 && !intel_syntax) as_warn (_("skipping prefixes on this instruction")); if (fits_in_unsigned_byte (i.tm.base_opcode)) @@ -2217,7 +2233,8 @@ md_assemble (line) } else { - insn_size += 2 + size; /* opcode can be at most two bytes */ + /* opcode can be at most two bytes */ + insn_size += 2 + size; p = frag_more (2 + size); *p++ = (i.tm.base_opcode >> 8) & 0xff; } @@ -2225,6 +2242,8 @@ md_assemble (line) if (i.disps[0]->X_op == O_constant) { + long n = (long) i.disps[0]->X_add_number; + if (size == 1 && !fits_in_signed_byte (n)) { as_bad (_("`%s' only takes byte displacement; %ld shortened to %d"), @@ -2248,16 +2267,20 @@ md_assemble (line) { int size; int reloc_type; - int prefix = i.prefix[DATA_PREFIX] != 0; - int code16 = 0; + int prefix; + int code16; - if (prefix) + code16 = 0; + if (flag_16bit_code) + code16 = CODE16; + + prefix = 0; + if (i.prefix[DATA_PREFIX]) { - code16 = CODE16; + prefix = 1; i.prefixes -= 1; + code16 ^= CODE16; } - if (flag_16bit_code) - code16 ^= CODE16; size = 4; reloc_type = BFD_RELOC_32; @@ -2267,7 +2290,7 @@ md_assemble (line) reloc_type = BFD_RELOC_16; } - if (!intel_syntax && (i.prefixes != 0)) + if (i.prefixes != 0 && !intel_syntax) as_warn (_("skipping prefixes on this instruction")); insn_size += prefix + 1 + 2 + size; /* 1 opcode; 2 segment; offset */ @@ -4235,7 +4258,6 @@ i386_target_format () #endif /* OBJ_MAYBE_ELF */ #endif /* BFD_ASSEMBLER */ -/* ARGSUSED */ symbolS * md_undefined_symbol (name) char *name; -- 2.30.2