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| author | Richard Henderson <richard.henderson@linaro.org> | 2018-05-08 19:18:59 +0000 |
|---|---|---|
| committer | Richard Henderson <richard.henderson@linaro.org> | 2018-05-09 08:30:57 -0700 |
| commit | abebf92597186be2bc48d487235da28b1127860f (patch) | |
| tree | cdc6b67dca81418f7e9ab2a67b8896676e655bb4 /tcg | |
| parent | 7eb30ef0ba2eb59e7430d4848ae8d4bf4e50f768 (diff) | |
| download | qemu-abebf92597186be2bc48d487235da28b1127860f.zip qemu-abebf92597186be2bc48d487235da28b1127860f.tar.gz qemu-abebf92597186be2bc48d487235da28b1127860f.tar.bz2 | |
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.c | 3 | ||||
| -rw-r--r-- | tcg/tcg.h | 8 |
2 files changed, 10 insertions, 1 deletions
@@ -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; } @@ -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 */ |