yuzu/unicorn
1
0
Fork 0
mirror of https://github.com/yuzu-emu/unicorn.git synced 2025-01-22 08:51:05 +00:00
Code Issues Packages Projects Releases Wiki Activity

tcg: Limit the number of ops in a TB

Browse source 
In 6001f7729e12 we partially attempt to address the branch
displacement overflow caused by 15fa08f845.

However, gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/vqtbX.c
is a testcase that contains a TB so large as to overflow anyway.
The limit here of 8000 ops produces a maximum output TB size of
24112 bytes on a ppc64le host with that test case. This is still
much less than the maximum forward branch distance of 32764 bytes.

Backports commit abebf92597186be2bc48d487235da28b1127860f from qemu
This commit is contained in:
Richard Henderson 2018-05-11 11:24:59 -04:00 committed by Lioncash
parent 33f7f6f09a
commit f417df19b7
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 10 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
qemu/tcg/tcg.c
View file

@ -504,6 +504,7 @@ void tcg_func_start(TCGContext *s)
/* No temps have been previously allocated for size or locality. */
memset(s->free_temps, 0, sizeof(s->free_temps));
s->nb_ops = 0;
s->nb_labels = 0;
s->current_frame_offset = s->frame_start;
@ -1677,6 +1678,7 @@ void tcg_op_remove(TCGContext *s, TCGOp *op)
{
QTAILQ_REMOVE(&s->ops, op, link);
QTAILQ_INSERT_TAIL(&s->free_ops, op, link);
s->nb_ops--;
#ifdef CONFIG_PROFILER
atomic_set(&s->prof.del_op_count, s->prof.del_op_count + 1);
@ -1695,6 +1697,7 @@ static TCGOp *tcg_op_alloc(TCGContext *s, TCGOpcode opc)
}
memset(op, 0, offsetof(TCGOp, link));
op->opc = opc;
s->nb_ops++;
return op;
}

8
qemu/tcg/tcg.h
View file

@ -723,6 +723,7 @@ struct TCGContext {
int nb_globals;
int nb_temps;
int nb_indirects;
int nb_ops;
/* goto_tb support */
tcg_insn_unit *code_buf;
@ -1055,7 +1056,12 @@ static inline TCGOp *tcg_last_op(TCGContext *tcg_ctx)
/* Test for whether to terminate the TB for using too many opcodes. */
static inline bool tcg_op_buf_full(TCGContext *tcg_ctx)
{
return false;
/* This is not a hard limit, it merely stops translation when
* we have produced "enough" opcodes. We want to limit TB size
* such that a RISC host can reasonably use a 16-bit signed
* branch within the TB.
*/
return tcg_ctx->nb_ops >= 8000;
}
TCGTemp *tcg_global_mem_new_internal(TCGContext *s, TCGType type, TCGv_ptr base,