[Qemu-devel] [PATCH v3 14/20] tcg-arm: Cleanup goto_tb handling

[Richard Henderson <rth@twiddle.net>]

Eliminate 2 disabled code blocks.  Choose the load-to-pc method of
jumping so that we can eliminate the 16M code_gen_buffer limitation.
Remove a test in the indirect jump method that is always true.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 include/exec/exec-all.h | 23 +++--------------------
 tcg/arm/tcg-target.c    | 26 ++++++--------------------
 translate-all.c         |  2 --
 3 files changed, 9 insertions(+), 42 deletions(-)

diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index e856191..190effa 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -233,26 +233,9 @@ static inline void tb_set_jmp_target1(uintptr_t jmp_addr, uintptr_t addr)
 #elif defined(__arm__)
 static inline void tb_set_jmp_target1(uintptr_t jmp_addr, uintptr_t addr)
 {
-#if !QEMU_GNUC_PREREQ(4, 1)
-    register unsigned long _beg __asm ("a1");
-    register unsigned long _end __asm ("a2");
-    register unsigned long _flg __asm ("a3");
-#endif
-
-    /* we could use a ldr pc, [pc, #-4] kind of branch and avoid the flush */
-    *(uint32_t *)jmp_addr =
-        (*(uint32_t *)jmp_addr & ~0xffffff)
-        | (((addr - (jmp_addr + 8)) >> 2) & 0xffffff);
-
-#if QEMU_GNUC_PREREQ(4, 1)
-    __builtin___clear_cache((char *) jmp_addr, (char *) jmp_addr + 4);
-#else
-    /* flush icache */
-    _beg = jmp_addr;
-    _end = jmp_addr + 4;
-    _flg = 0;
-    __asm __volatile__ ("swi 0x9f0002" : : "r" (_beg), "r" (_end), "r" (_flg));
-#endif
+    /* We're using "ldr pc, [pc,#-4]", so we can just store the raw
+       address, without caring for flushing the icache.  */
+    *(uint32_t *)jmp_addr = addr;
 }
 #elif defined(__sparc__)
 void tb_set_jmp_target1(uintptr_t jmp_addr, uintptr_t addr);
diff --git a/tcg/arm/tcg-target.c b/tcg/arm/tcg-target.c
index 7bcba19..6de5e90 100644
--- a/tcg/arm/tcg-target.c
+++ b/tcg/arm/tcg-target.c
@@ -1595,30 +1595,16 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
         break;
     case INDEX_op_goto_tb:
         if (s->tb_jmp_offset) {
-            /* Direct jump method */
-#if defined(USE_DIRECT_JUMP)
-            s->tb_jmp_offset[args[0]] = s->code_ptr - s->code_buf;
-            tcg_out_b_noaddr(s, COND_AL);
-#else
+            /* "Direct" jump method.  Rather than limit the code gen buffer
+               to 16M, load the destination from the next word.  */
             tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_PC, -4);
             s->tb_jmp_offset[args[0]] = s->code_ptr - s->code_buf;
-            tcg_out32(s, 0);
-#endif
+            s->code_ptr += 4;
         } else {
-            /* Indirect jump method */
-#if 1
-            c = (int) (s->tb_next + args[0]) - ((int) s->code_ptr + 8);
-            if (c > 0xfff || c < -0xfff) {
-                tcg_out_movi32(s, COND_AL, TCG_REG_R0,
-                                (tcg_target_long) (s->tb_next + args[0]));
-                tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_R0, 0);
-            } else
-                tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_PC, c);
-#else
-            tcg_out_ld32_12(s, COND_AL, TCG_REG_R0, TCG_REG_PC, 0);
+            /* Indirect jump method.  */
+            tcg_out_movi32(s, COND_AL, TCG_REG_R0,
+                           (tcg_target_long) (s->tb_next + args[0]));
             tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_R0, 0);
-            tcg_out32(s, (tcg_target_long) (s->tb_next + args[0]));
-#endif
         }
         s->tb_next_offset[args[0]] = s->code_ptr - s->code_buf;
         break;
diff --git a/translate-all.c b/translate-all.c
index a98c646..3ca839f 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -460,8 +460,6 @@ static inline PageDesc *page_find(tb_page_addr_t index)
 # define MAX_CODE_GEN_BUFFER_SIZE  (2ul * 1024 * 1024 * 1024)
 #elif defined(__sparc__)
 # define MAX_CODE_GEN_BUFFER_SIZE  (2ul * 1024 * 1024 * 1024)
-#elif defined(__arm__)
-# define MAX_CODE_GEN_BUFFER_SIZE  (16u * 1024 * 1024)
 #elif defined(__s390x__)
   /* We have a +- 4GB range on the branches; leave some slop.  */
 # define MAX_CODE_GEN_BUFFER_SIZE  (3ul * 1024 * 1024 * 1024)
-- 
1.8.1.4