[PATCH v2] tcg: Reset free_temps before tcg_optimize

[Richard Henderson]

When allocating new temps during tcg_optmize, do not re-use
any EBB temps that were used within the TB.  We do not have
any idea what span of the TB in which the temp was live.

Introduce tcg_temp_ebb_reset_freed and use before tcg_optimize,
as well as replacing the equivalent in plugin_gen_inject and
tcg_func_start.

Cc: qemu-stable@nongnu.org
Fixes: fb04ab7ddd8 ("tcg/optimize: Lower TCG_COND_TST{EQ,NE} if unsupported")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2711
Reported-by: wannacu <wannacu2049@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 include/tcg/tcg-temp-internal.h | 6 ++++++
 accel/tcg/plugin-gen.c          | 2 +-
 tcg/tcg.c                       | 5 ++++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/tcg/tcg-temp-internal.h b/include/tcg/tcg-temp-internal.h
index 44192c55a9..98f91e68b7 100644
--- a/include/tcg/tcg-temp-internal.h
+++ b/include/tcg/tcg-temp-internal.h
@@ -42,4 +42,10 @@ TCGv_i64 tcg_temp_ebb_new_i64(void);
 TCGv_ptr tcg_temp_ebb_new_ptr(void);
 TCGv_i128 tcg_temp_ebb_new_i128(void);
 
+/* Forget all freed EBB temps, so that new allocations produce new temps. */
+static inline void tcg_temp_ebb_reset_freed(TCGContext *s)
+{
+    memset(s->free_temps, 0, sizeof(s->free_temps));
+}
+
 #endif /* TCG_TEMP_FREE_H */
diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
index 0f47bfbb48..1ef075552c 100644
--- a/accel/tcg/plugin-gen.c
+++ b/accel/tcg/plugin-gen.c
@@ -275,7 +275,7 @@ static void plugin_gen_inject(struct qemu_plugin_tb 
*plugin_tb)
      * that might be live within the existing opcode stream.
      * The simplest solution is to release them all and create new.
      */
-    memset(tcg_ctx->free_temps, 0, sizeof(tcg_ctx->free_temps));
+    tcg_temp_ebb_reset_freed(tcg_ctx);
 
     QTAILQ_FOREACH_SAFE(op, &tcg_ctx->ops, link, next) {
         switch (op->opc) {
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 0babae1b88..4578b185be 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1489,7 +1489,7 @@ void tcg_func_start(TCGContext *s)
     s->nb_temps = s->nb_globals;
 
     /* No temps have been previously allocated for size or locality.  */
-    memset(s->free_temps, 0, sizeof(s->free_temps));
+    tcg_temp_ebb_reset_freed(s);
 
     /* No constant temps have been previously allocated. */
     for (int i = 0; i < TCG_TYPE_COUNT; ++i) {
@@ -6120,6 +6120,9 @@ int tcg_gen_code(TCGContext *s, TranslationBlock *tb, 
uint64_t pc_start)
     }
 #endif
 
+    /* Do not reuse any EBB that may be allocated within the TB. */
+    tcg_temp_ebb_reset_freed(s);
+
     tcg_optimize(s);
 
     reachable_code_pass(s);
-- 
2.43.0