There are places, like brcond2, where we know that the destination
of a forward branch will be within 127 bytes. Add the R_386_PC8
relocation type to support this, and add a flag to tcg_out_jxx to
generate it. Set the flag in the small forward branches in brcond2.
Signed-off-by: Richard Henderson <r...@twiddle.net>
---
elf.h | 2 ++
tcg/i386/tcg-target.c | 36 +++++++++++++++++++++++++-----------
2 files changed, 27 insertions(+), 11 deletions(-)
diff --git a/elf.h b/elf.h
index 11674d7..c84c8ab 100644
--- a/elf.h
+++ b/elf.h
@@ -243,6 +243,8 @@ typedef struct {
#define R_386_GOTOFF 9
#define R_386_GOTPC 10
#define R_386_NUM 11
+/* Not a dynamic reloc, so not included in R_386_NUM. Used in TCG. */
+#define R_386_PC8 23
#define R_MIPS_NONE 0
#define R_MIPS_16 1
diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index 972b102..cc3d28f 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -61,6 +61,9 @@ static void patch_reloc(uint8_t *code_ptr, int type,
case R_386_PC32:
*(uint32_t *)code_ptr = value - (long)code_ptr;
break;
+ case R_386_PC8:
+ *(uint8_t *)code_ptr = value - (long)code_ptr;
+ break;
default:
tcg_abort();
}
@@ -305,7 +308,8 @@ static void tcg_out_addi(TCGContext *s, int reg,
tcg_target_long val)
tgen_arithi(s, ARITH_ADD, reg, val, 0);
}
-static void tcg_out_jxx(TCGContext *s, int opc, int label_index)
+/* Use SMALL != 0 to force a short forward branch. */
+static void tcg_out_jxx(TCGContext *s, int opc, int label_index, int small)
{
int32_t val, val1;
TCGLabel *l = &s->labels[label_index];
@@ -320,6 +324,7 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
label_index)
tcg_out8(s, 0x70 + opc);
tcg_out8(s, val1);
} else {
+ assert (!small);
if (opc == -1) {
tcg_out8(s, 0xe9);
tcg_out32(s, val - 5);
@@ -329,6 +334,15 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
label_index)
tcg_out32(s, val - 6);
}
}
+ } else if (small) {
+ if (opc == -1) {
+ tcg_out8(s, 0xeb);
+ } else {
+ tcg_out8(s, 0x0f);
+ tcg_out8(s, 0x70 + opc);
+ }
+ tcg_out_reloc(s, s->code_ptr, R_386_PC8, label_index, -1);
+ s->code_ptr += 1;
} else {
if (opc == -1) {
tcg_out8(s, 0xe9);
@@ -355,7 +369,7 @@ static void tcg_out_brcond(TCGContext *s, int cond,
} else {
tcg_out_modrm(s, 0x01 | (ARITH_CMP << 3), arg2, arg1);
}
- tcg_out_jxx(s, tcg_cond_to_jcc[cond], label_index);
+ tcg_out_jxx(s, tcg_cond_to_jcc[cond], label_index, 0);
}
/* XXX: we implement it at the target level to avoid having to
@@ -376,42 +390,42 @@ static void tcg_out_brcond2(TCGContext *s,
break;
case TCG_COND_LT:
tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_LE:
tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_GT:
tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_GE:
tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_LTU:
tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_LEU:
tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_GTU:
tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
args[5]);
break;
case TCG_COND_GEU:
tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
args[5]);
- tcg_out_jxx(s, JCC_JNE, label_next);
+ tcg_out_jxx(s, JCC_JNE, label_next, 1);
tcg_out_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
args[5]);
break;
default:
@@ -913,7 +927,7 @@ static inline void tcg_out_op(TCGContext *s, int opc,
}
break;
case INDEX_op_br:
- tcg_out_jxx(s, JCC_JMP, args[0]);
+ tcg_out_jxx(s, JCC_JMP, args[0], 0);
break;
case INDEX_op_movi_i32:
tcg_out_movi(s, TCG_TYPE_I32, args[0], args[1]);
--
1.6.5.2
