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target/arm: Perform per-insn cross-page check only for Thumb

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ARM is a fixed-length ISA and we can compute the page crossing
condition exactly once during init_disas_context.

Backports commit d0264d86b026e9d948de577b05ff86d708658576 from qemu
This commit is contained in:
Richard Henderson 2018-03-04 20:42:19 -05:00 committed by Lioncash
parent ab21785d3f
commit 6d2bcf6ed8
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 33 additions and 24 deletions
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57
qemu/target/arm/translate.c
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@ -12098,6 +12098,13 @@ static int arm_tr_init_disas_context(DisasContextBase *dcbase,
max_insns = 1;
}
/* ARM is a fixed-length ISA. Bound the number of insns to execute
to those left on the page. */
if (!dc->thumb) {
int bound = (dc->next_page_start - dc->base.pc_first) / 4;
max_insns = MIN(max_insns, bound);
}
tcg_ctx->cpu_F0s = tcg_temp_new_i32(tcg_ctx);
tcg_ctx->cpu_F1s = tcg_temp_new_i32(tcg_ctx);
tcg_ctx->cpu_F0d = tcg_temp_new_i64(tcg_ctx);
@ -12229,7 +12236,7 @@ static bool arm_pre_translate_insn(DisasContext *dc)
return false;
}
static void arm_post_translate_insn(CPUARMState *env, DisasContext *dc)
static void arm_post_translate_insn(DisasContext *dc)
{
TCGContext *tcg_ctx = dc->uc->tcg_ctx;
@ -12238,27 +12245,6 @@ static void arm_post_translate_insn(CPUARMState *env, DisasContext *dc)
dc->condjmp = 0;
}
/* Translation stops when a conditional branch is encountered.
* Otherwise the subsequent code could get translated several times.
* Also stop translation when a page boundary is reached. This
* ensures prefetch aborts occur at the right place.
*
* We want to stop the TB if the next insn starts in a new page,
* or if it spans between this page and the next. This means that
* if we're looking at the last halfword in the page we need to
* see if it's a 16-bit Thumb insn (which will fit in this TB)
* or a 32-bit Thumb insn (which won't).
* This is to avoid generating a silly TB with a single 16-bit insn
* in it at the end of this page (which would execute correctly
* but isn't very efficient).
*/
if (dc->base.is_jmp == DISAS_NEXT
&& (dc->pc >= dc->next_page_start
|| (dc->pc >= dc->next_page_start - 3
&& insn_crosses_page(env, dc)))) {
dc->base.is_jmp = DISAS_TOO_MANY;
}
dc->base.pc_next = dc->pc;
translator_loop_temp_check(&dc->base);
}
@ -12277,7 +12263,10 @@ static void arm_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
dc->pc += 4;
disas_arm_insn(dc, insn);
arm_post_translate_insn(env, dc);
arm_post_translate_insn(dc);
/* ARM is a fixed-length ISA. We performed the cross-page check
in init_disas_context by adjusting max_insns. */
}
static void thumb_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
@ -12301,7 +12290,27 @@ static void thumb_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
}
}
arm_post_translate_insn(env, dc);
arm_post_translate_insn(dc);
/* Thumb is a variable-length ISA. Stop translation when the next insn
* will touch a new page. This ensures that prefetch aborts occur at
* the right place.
*
* We want to stop the TB if the next insn starts in a new page,
* or if it spans between this page and the next. This means that
* if we're looking at the last halfword in the page we need to
* see if it's a 16-bit Thumb insn (which will fit in this TB)
* or a 32-bit Thumb insn (which won't).
* This is to avoid generating a silly TB with a single 16-bit insn
* in it at the end of this page (which would execute correctly
* but isn't very efficient).
*/
if (dc->base.is_jmp == DISAS_NEXT
&& (dc->pc >= dc->next_page_start
|| (dc->pc >= dc->next_page_start - 3
&& insn_crosses_page(env, dc)))) {
dc->base.is_jmp = DISAS_TOO_MANY;
}
}
static void arm_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)