Revert "accel/tcg: Reduce CF_COUNT_MASK to match TCG_MAX_INSNS"

Commit Message

Richard Henderson July 24, 2021, 11:27 p.m. UTC

This reverts commit 78ff82bb1b67c0d79113688e4b3427fc99cab9d4.

This produces transient errors in the 2018 advent calendar day 11
image for sparc when using -icount auto.

It is not clear what the problem is with the narrower CF_COUNT_MASK
value, since we bound the insns_left value in cpu_loop_exec_tb and
we bound the insns translated in tb_gen_code.  But it is late in the
release cycle and reverting the change does fix the problem.

In the meantime, CF_NO_GOTO_TB, CF_NO_GOTO_PTR and CF_SINGLE_STEP
were added and so need to be moved to different bits.

Reported-by: Peter Maydell <[e-mail]>
Signed-off-by: Richard Henderson <[e-mail]>
---
 include/exec/exec-all.h   | 9 ++++-----
 accel/tcg/translate-all.c | 4 +++-
 2 files changed, 7 insertions(+), 6 deletions(-)

Patch

diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 5d1b6d80fb..bccd7724dc 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -493,16 +493,15 @@  struct TranslationBlock {
     uint32_t flags; /* flags defining in which context the code was generated */
     uint32_t cflags;    /* compile flags */
 
-/* Note that TCG_MAX_INSNS is 512; we validate this match elsewhere. */
-#define CF_COUNT_MASK    0x000001ff
-#define CF_NO_GOTO_TB    0x00000200 /* Do not chain with goto_tb */
-#define CF_NO_GOTO_PTR   0x00000400 /* Do not chain with goto_ptr */
-#define CF_SINGLE_STEP   0x00000800 /* gdbstub single-step in effect */
+#define CF_COUNT_MASK    0x00007fff
 #define CF_LAST_IO       0x00008000 /* Last insn may be an IO access.  */
 #define CF_MEMI_ONLY     0x00010000 /* Only instrument memory ops */
 #define CF_USE_ICOUNT    0x00020000
 #define CF_INVALID       0x00040000 /* TB is stale. Set with @jmp_lock held */
 #define CF_PARALLEL      0x00080000 /* Generate code for a parallel context */
+#define CF_NO_GOTO_TB    0x00100000 /* Do not chain with goto_tb */
+#define CF_NO_GOTO_PTR   0x00200000 /* Do not chain with goto_ptr */
+#define CF_SINGLE_STEP   0x00400000 /* gdbstub single-step in effect */
 #define CF_CLUSTER_MASK  0xff000000 /* Top 8 bits are cluster ID */
 #define CF_CLUSTER_SHIFT 24
 
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index bbfcfb698c..0226123981 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1428,9 +1428,11 @@  TranslationBlock *tb_gen_code(CPUState *cpu,
 
     max_insns = cflags & CF_COUNT_MASK;
     if (max_insns == 0) {
+        max_insns = CF_COUNT_MASK;
+    }
+    if (max_insns > TCG_MAX_INSNS) {
         max_insns = TCG_MAX_INSNS;
     }
-    QEMU_BUILD_BUG_ON(CF_COUNT_MASK + 1 != TCG_MAX_INSNS);
 
  buffer_overflow:
     tb = tcg_tb_alloc(tcg_ctx);