From e4dfb7f807a4d936929f67b9bc92d278cbeec54f Mon Sep 17 00:00:00 2001
From: "Emilio G. Cota" <cota@braap.org>
Date: Fri, 2 Mar 2018 21:07:42 -0500
Subject: [PATCH] tcg/i386: implement goto_ptr

Backports commit 5cb4ef80f65252dd85b86fa7f3c985015423d670 from qemu
---
 qemu/tcg/i386/tcg-target.h     |  2 +-
 qemu/tcg/i386/tcg-target.inc.c | 24 ++++++++++++++++++++++--
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/qemu/tcg/i386/tcg-target.h b/qemu/tcg/i386/tcg-target.h
index 568d3f1f..ca528d76 100644
--- a/qemu/tcg/i386/tcg-target.h
+++ b/qemu/tcg/i386/tcg-target.h
@@ -107,7 +107,7 @@ extern bool have_popcnt;
 #define TCG_TARGET_HAS_muls2_i32        1
 #define TCG_TARGET_HAS_muluh_i32        0
 #define TCG_TARGET_HAS_mulsh_i32        0
-#define TCG_TARGET_HAS_goto_ptr         0
+#define TCG_TARGET_HAS_goto_ptr         1
 
 #if TCG_TARGET_REG_BITS == 64
 #define TCG_TARGET_HAS_extrl_i64_i32    0
diff --git a/qemu/tcg/i386/tcg-target.inc.c b/qemu/tcg/i386/tcg-target.inc.c
index abe7343a..139bf675 100644
--- a/qemu/tcg/i386/tcg-target.inc.c
+++ b/qemu/tcg/i386/tcg-target.inc.c
@@ -1979,8 +1979,13 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
 
     switch(opc) {
     case INDEX_op_exit_tb:
-        tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_EAX, a0);
-        tcg_out_jmp(s, s->tb_ret_addr);
+        /* Reuse the zeroing that exists for goto_ptr.  */
+        if (a0 == 0) {
+            tcg_out_jmp(s, s->code_gen_epilogue);
+        } else {
+            tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_EAX, a0);
+            tcg_out_jmp(s, s->tb_ret_addr);
+        }
         break;
     case INDEX_op_goto_tb:
         if (s->tb_jmp_insn_offset) {
@@ -2003,6 +2008,10 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
         }
         s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s);
         break;
+    case INDEX_op_goto_ptr:
+        /* jmp to the given host address (could be epilogue) */
+        tcg_out_modrm(s, OPC_GRP5, EXT5_JMPN_Ev, a0);
+        break;
     case INDEX_op_br:
         tcg_out_jxx(s, JCC_JMP, arg_label(s, a0), 0);
         break;
@@ -2374,6 +2383,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
 
 static const TCGTargetOpDef *tcg_target_op_def(TCGOpcode op)
 {
+    static const TCGTargetOpDef r = { 0, { "r" } };
     static const TCGTargetOpDef ri_r = { 0, { "ri", "r" } };
     static const TCGTargetOpDef re_r = { 0, { "re", "r" } };
     static const TCGTargetOpDef qi_r = { 0, { "qi", "r" } };
@@ -2394,6 +2404,9 @@ static const TCGTargetOpDef *tcg_target_op_def(TCGOpcode op)
     static const TCGTargetOpDef L_L_L_L = { 0, { "L", "L", "L", "L" } };
 
     switch (op) {
+    case INDEX_op_goto_ptr:
+        return &r;
+
     case INDEX_op_ld8u_i32:
     case INDEX_op_ld8u_i64:
     case INDEX_op_ld8s_i32:
@@ -2653,6 +2666,13 @@ static void tcg_target_qemu_prologue(TCGContext *s)
     tcg_out_modrm(s, OPC_GRP5, EXT5_JMPN_Ev, tcg_target_call_iarg_regs[1]);
 #endif
 
+    /*
+     * Return path for goto_ptr. Set return value to 0, a-la exit_tb,
+     * and fall through to the rest of the epilogue.
+     */
+    s->code_gen_epilogue = s->code_ptr;
+    tcg_out_movi(s, TCG_TYPE_REG, TCG_REG_EAX, 0);
+
     /* TB epilogue */
     s->tb_ret_addr = s->code_ptr;