[Qemu-devel] [PATCH v3 2/4] tcg: reorganize tb_find_physical loop

[Sergey Fedorov <sergey.fedorov@linaro.org>]

From: Alex Bennée <alex.bennee@linaro.org>

Put some comments and improve code structure. This should help reading
the code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
[Sergey Fedorov: provide commit message; bring back resetting of
tb_invalidated_flag]
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Richard Henderson  <rth@twiddle.net>
---
 cpu-exec.c | 44 ++++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index bbfcbfb54385..4cba4efc92b2 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -223,10 +223,9 @@ static TranslationBlock *tb_find_physical(CPUState *cpu,
                                           uint64_t flags)
 {
     CPUArchState *env = (CPUArchState *)cpu->env_ptr;
-    TranslationBlock *tb, **ptb1;
+    TranslationBlock *tb, **tb_hash_head, **ptb1;
     unsigned int h;
     tb_page_addr_t phys_pc, phys_page1;
-    target_ulong virt_page2;
 
     tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
 
@@ -234,37 +233,42 @@ static TranslationBlock *tb_find_physical(CPUState *cpu,
     phys_pc = get_page_addr_code(env, pc);
     phys_page1 = phys_pc & TARGET_PAGE_MASK;
     h = tb_phys_hash_func(phys_pc);
-    ptb1 = &tcg_ctx.tb_ctx.tb_phys_hash[h];
-    for(;;) {
-        tb = *ptb1;
-        if (!tb) {
-            return NULL;
-        }
+
+    /* Start at head of the hash entry */
+    ptb1 = tb_hash_head = &tcg_ctx.tb_ctx.tb_phys_hash[h];
+    tb = *ptb1;
+
+    while (tb) {
         if (tb->pc == pc &&
             tb->page_addr[0] == phys_page1 &&
             tb->cs_base == cs_base &&
             tb->flags == flags) {
-            /* check next page if needed */
-            if (tb->page_addr[1] != -1) {
-                tb_page_addr_t phys_page2;
 
-                virt_page2 = (pc & TARGET_PAGE_MASK) +
-                    TARGET_PAGE_SIZE;
-                phys_page2 = get_page_addr_code(env, virt_page2);
+            if (tb->page_addr[1] == -1) {
+                /* done, we have a match */
+                break;
+            } else {
+                /* check next page if needed */
+                target_ulong virt_page2 = (pc & TARGET_PAGE_MASK) +
+                                          TARGET_PAGE_SIZE;
+                tb_page_addr_t phys_page2 = get_page_addr_code(env, virt_page2);
+
                 if (tb->page_addr[1] == phys_page2) {
                     break;
                 }
-            } else {
-                break;
             }
         }
+
         ptb1 = &tb->phys_hash_next;
+        tb = *ptb1;
     }
 
-    /* Move the TB to the head of the list */
-    *ptb1 = tb->phys_hash_next;
-    tb->phys_hash_next = tcg_ctx.tb_ctx.tb_phys_hash[h];
-    tcg_ctx.tb_ctx.tb_phys_hash[h] = tb;
+    if (tb) {
+        /* Move the TB to the head of the list */
+        *ptb1 = tb->phys_hash_next;
+        tb->phys_hash_next = *tb_hash_head;
+        *tb_hash_head = tb;
+    }
     return tb;
 }
 
-- 
2.8.1