From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42477) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fG8Ps-0005U1-3q for qemu-devel@nongnu.org; Tue, 08 May 2018 15:36:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fG8Pp-0001Sv-5t for qemu-devel@nongnu.org; Tue, 08 May 2018 15:36:52 -0400 Received: from mail-pg0-x241.google.com ([2607:f8b0:400e:c05::241]:35461) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fG8Po-0001SK-Vx for qemu-devel@nongnu.org; Tue, 08 May 2018 15:36:49 -0400 Received: by mail-pg0-x241.google.com with SMTP id j11-v6so21597727pgf.2 for ; Tue, 08 May 2018 12:36:48 -0700 (PDT) From: Richard Henderson Date: Tue, 8 May 2018 12:36:45 -0700 Message-Id: <20180508193645.3960-1-richard.henderson@linaro.org> Subject: [Qemu-devel] [PATCH] tcg: Limit the number of ops in a TB List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, laurent@vivier.eu, qemu-stable@nongnu.org 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") Signed-off-by: Richard Henderson --- tcg/tcg.h | 8 +++++++- tcg/tcg.c | 3 +++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/tcg/tcg.h b/tcg/tcg.h index 75fbad128b..88378be310 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 */ diff --git a/tcg/tcg.c b/tcg/tcg.c index 551caf1c53..6eeebe0624 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; } -- 2.17.0