Re: [PATCH for-5.0?] target/xtensa: Statically allocate xtensa_insnbufs

[Max Filippov]

On Mon, Apr 6, 2020 at 8:09 PM Richard Henderson
<address@hidden> wrote:
>
> Rather than dynamically allocate, and risk failing to free
> when we longjmp out of the translator, allocate the maximum
> buffer size from any of the supported cpus, which is 8:

There's macro MAX_INSN_LENGTH that defines maximal supported
instruction length in bytes. Maybe the following instead, along the lines
of what libisa does dynamically?:

--8<--
>From 08cc91b0d51e244766d73aae23aebd194b598378 Mon Sep 17 00:00:00 2001
From: Max Filippov <address@hidden>
Date: Mon, 6 Apr 2020 20:59:54 -0700
Subject: [PATCH] target/xtensa: statically allocate xtensa_insnbufs in
DisasContext

Signed-off-by: Max Filippov <address@hidden>
---
 target/xtensa/cpu.h       |  3 +++
 target/xtensa/helper.c    |  1 +
 target/xtensa/translate.c | 12 ++----------
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/target/xtensa/cpu.h b/target/xtensa/cpu.h
index c0d69fad96c5..7a46dccbe11b 100644
--- a/target/xtensa/cpu.h
+++ b/target/xtensa/cpu.h
@@ -213,6 +213,9 @@ enum {
 #define MEMCTL_IL0EN 0x1

 #define MAX_INSN_LENGTH 64
+#define MAX_INSNBUF_LENGTH \
+    ((MAX_INSN_LENGTH + sizeof(xtensa_insnbuf_word) - 1) / \
+     sizeof(xtensa_insnbuf_word))
 #define MAX_INSN_SLOTS 32
 #define MAX_OPCODE_ARGS 16
 #define MAX_NAREG 64
diff --git a/target/xtensa/helper.c b/target/xtensa/helper.c
index 376a61f3397c..278415ae0e06 100644
--- a/target/xtensa/helper.c
+++ b/target/xtensa/helper.c
@@ -96,6 +96,7 @@ static void init_libisa(XtensaConfig *config)

     config->isa = xtensa_isa_init(config->isa_internal, NULL, NULL);
     assert(xtensa_isa_maxlength(config->isa) <= MAX_INSN_LENGTH);
+    assert(xtensa_insnbuf_size(dc->config->isa) <= MAX_INSNBUF_LENGTH);
     opcodes = xtensa_isa_num_opcodes(config->isa);
     formats = xtensa_isa_num_formats(config->isa);
     regfiles = xtensa_isa_num_regfiles(config->isa);
diff --git a/target/xtensa/translate.c b/target/xtensa/translate.c
index 8aa972cafdf3..91c7776c2544 100644
--- a/target/xtensa/translate.c
+++ b/target/xtensa/translate.c
@@ -72,8 +72,8 @@ struct DisasContext {
     unsigned cpenable;

     uint32_t op_flags;
-    xtensa_insnbuf insnbuf;
-    xtensa_insnbuf slotbuf;
+    xtensa_insnbuf_word insnbuf[MAX_INSNBUF_LENGTH];
+    xtensa_insnbuf_word slotbuf[MAX_INSNBUF_LENGTH];
 };

 static TCGv_i32 cpu_pc;
@@ -1174,10 +1174,6 @@ static void
xtensa_tr_init_disas_context(DisasContextBase *dcbase,
     dc->callinc = ((tb_flags & XTENSA_TBFLAG_CALLINC_MASK) >>
                    XTENSA_TBFLAG_CALLINC_SHIFT);

-    if (dc->config->isa) {
-        dc->insnbuf = xtensa_insnbuf_alloc(dc->config->isa);
-        dc->slotbuf = xtensa_insnbuf_alloc(dc->config->isa);
-    }
     init_sar_tracker(dc);
 }

@@ -1267,10 +1263,6 @@ static void xtensa_tr_tb_stop(DisasContextBase
*dcbase, CPUState *cpu)
     DisasContext *dc = container_of(dcbase, DisasContext, base);

     reset_sar_tracker(dc);
-    if (dc->config->isa) {
-        xtensa_insnbuf_free(dc->config->isa, dc->insnbuf);
-        xtensa_insnbuf_free(dc->config->isa, dc->slotbuf);
-    }
     if (dc->icount) {
         tcg_temp_free(dc->next_icount);
     }
--8<--
-- 
Thanks.
-- Max