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authorRichard Henderson <richard.henderson@linaro.org>2018-05-08 19:18:59 +0000
committerRichard Henderson <richard.henderson@linaro.org>2018-05-09 08:30:57 -0700
commitabebf92597186be2bc48d487235da28b1127860f (patch)
treecdc6b67dca81418f7e9ab2a67b8896676e655bb4 /tcg
parent7eb30ef0ba2eb59e7430d4848ae8d4bf4e50f768 (diff)
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tcg: Limit the number of ops in a TB
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. Cc: qemu-stable@nongnu.org Fixes: 15fa08f845 ("tcg: Dynamically allocate TCGOps") Reviewed-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'tcg')
-rw-r--r--tcg/tcg.c3
-rw-r--r--tcg/tcg.h8
2 files changed, 10 insertions, 1 deletions
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 551caf1..6eeebe0 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -866,6 +866,7 @@ 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;
@@ -1956,6 +1957,7 @@ 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);
@@ -1975,6 +1977,7 @@ static TCGOp *tcg_op_alloc(TCGOpcode opc)
}
memset(op, 0, offsetof(TCGOp, link));
op->opc = opc;
+ s->nb_ops++;
return op;
}
diff --git a/tcg/tcg.h b/tcg/tcg.h
index 75fbad1..88378be 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -655,6 +655,7 @@ struct TCGContext {
int nb_globals;
int nb_temps;
int nb_indirects;
+ int nb_ops;
/* goto_tb support */
tcg_insn_unit *code_buf;
@@ -844,7 +845,12 @@ static inline TCGOp *tcg_last_op(void)
/* Test for whether to terminate the TB for using too many opcodes. */
static inline bool tcg_op_buf_full(void)
{
- 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;
}
/* pool based memory allocation */