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[Qemu-devel] [PATCH 1/2] tcg-i386: Implement small forward branches.
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From: |
Richard Henderson |
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Subject: |
[Qemu-devel] [PATCH 1/2] tcg-i386: Implement small forward branches. |
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Date: |
Sat, 6 Feb 2010 11:47:58 -0800 |
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. Add a flag to
tcg_out_jxx and tcg_out_brcond* to enable it. Set the flag in the
brcond2 label_next branches; pass along the input flag otherwise.
Signed-off-by: Richard Henderson <address@hidden>
---
elf.h | 2 +
tcg/i386/tcg-target.c | 117 +++++++++++++++++++++++++++++++++----------------
2 files changed, 81 insertions(+), 38 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..052af49 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -61,6 +61,13 @@ 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:
+ value -= (long)code_ptr;
+ if (value != (int8_t)value) {
+ tcg_abort();
+ }
+ *(uint8_t *)code_ptr = value;
+ break;
default:
tcg_abort();
}
@@ -305,7 +312,8 @@ 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];
@@ -314,12 +322,16 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
label_index)
val = l->u.value - (tcg_target_long)s->code_ptr;
val1 = val - 2;
if ((int8_t)val1 == val1) {
- if (opc == -1)
+ if (opc == -1) {
tcg_out8(s, 0xeb);
- else
+ } else {
tcg_out8(s, 0x70 + opc);
+ }
tcg_out8(s, val1);
} else {
+ if (small) {
+ tcg_abort();
+ }
if (opc == -1) {
tcg_out8(s, 0xe9);
tcg_out32(s, val - 5);
@@ -329,6 +341,14 @@ 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, 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);
@@ -343,7 +363,7 @@ static void tcg_out_jxx(TCGContext *s, int opc, int
label_index)
static void tcg_out_brcond(TCGContext *s, int cond,
TCGArg arg1, TCGArg arg2, int const_arg2,
- int label_index)
+ int label_index, int small)
{
if (const_arg2) {
if (arg2 == 0) {
@@ -355,64 +375,84 @@ 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, small);
}
/* XXX: we implement it at the target level to avoid having to
handle cross basic blocks temporaries */
-static void tcg_out_brcond2(TCGContext *s,
- const TCGArg *args, const int *const_args)
+static void tcg_out_brcond2(TCGContext *s, const TCGArg *args,
+ const int *const_args, int small)
{
int label_next;
label_next = gen_new_label();
switch(args[4]) {
case TCG_COND_EQ:
- tcg_out_brcond(s, TCG_COND_NE, args[0], args[2], const_args[2],
label_next);
- tcg_out_brcond(s, TCG_COND_EQ, args[1], args[3], const_args[3],
args[5]);
+ tcg_out_brcond(s, TCG_COND_NE, args[0], args[2], const_args[2],
+ label_next, 1);
+ tcg_out_brcond(s, TCG_COND_EQ, args[1], args[3], const_args[3],
+ args[5], small);
break;
case TCG_COND_NE:
- tcg_out_brcond(s, TCG_COND_NE, args[0], args[2], const_args[2],
args[5]);
- tcg_out_brcond(s, TCG_COND_NE, args[1], args[3], const_args[3],
args[5]);
+ tcg_out_brcond(s, TCG_COND_NE, args[0], args[2], const_args[2],
+ args[5], small);
+ tcg_out_brcond(s, TCG_COND_NE, args[1], args[3], const_args[3],
+ args[5], small);
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_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_LT, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_GT, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_LTU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_LEU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_LTU, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_GTU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
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_brcond(s, TCG_COND_GEU, args[0], args[2], const_args[2],
args[5]);
+ tcg_out_brcond(s, TCG_COND_GTU, args[1], args[3], const_args[3],
+ args[5], small);
+ 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], small);
break;
default:
tcg_abort();
@@ -913,7 +953,7 @@ 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]);
@@ -1044,10 +1084,11 @@ static inline void tcg_out_op(TCGContext *s, int opc,
tcg_out_modrm(s, 0x01 | (ARITH_SBB << 3), args[5], args[1]);
break;
case INDEX_op_brcond_i32:
- tcg_out_brcond(s, args[2], args[0], args[1], const_args[1], args[3]);
+ tcg_out_brcond(s, args[2], args[0], args[1], const_args[1],
+ args[3], 0);
break;
case INDEX_op_brcond2_i32:
- tcg_out_brcond2(s, args, const_args);
+ tcg_out_brcond2(s, args, const_args, 0);
break;
case INDEX_op_bswap16_i32:
--
1.6.6