Re: [Qemu-devel] [PATCH 06/10] Revived GUEST_BASE support for usermode emulation targets [v2]

[malc]

On Wed, 29 Apr 2009, address@hidden wrote:

> From: Mika Westerberg <address@hidden>
> 
> From: Mika Westerberg <address@hidden>
> 
> - Now GUEST_BASE is dynamic and can be set from command line.
> - Qemu checks /proc/sys/vm/mmap_min_addr and sets GUEST_BASE
>   if needed.
> - Code generation supports GUEST_BASE for i386 and x86_64 hosts.
> 
> [v2]: implemented GUEST_BASE with single LEA
> 
> Changed TCG (on x86 and x86_64) to generate single LEA instead

After actually considering the whole picture neither MOV+ADD nor LEA
are needed at all, something like the following (i386 case, and not
tested):

diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index e0fd434..f17bca0 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -22,6 +22,10 @@
  * THE SOFTWARE.
  */
 
+#ifndef CONFIG_USE_GUEST_BASE
+#define GUEST_BASE 0
+#endif
+
 #ifndef NDEBUG
 static const char * const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
     "%eax",
@@ -572,15 +576,15 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg 
*args,
     switch(opc) {
     case 0:
         /* movzbl */
-        tcg_out_modrm_offset(s, 0xb6 | P_EXT, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0xb6 | P_EXT, data_reg, r0, GUEST_BASE);
         break;
     case 0 | 4:
         /* movsbl */
-        tcg_out_modrm_offset(s, 0xbe | P_EXT, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0xbe | P_EXT, data_reg, r0, GUEST_BASE);
         break;
     case 1:
         /* movzwl */
-        tcg_out_modrm_offset(s, 0xb7 | P_EXT, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0xb7 | P_EXT, data_reg, r0, GUEST_BASE);
         if (bswap) {
             /* rolw $8, data_reg */
             tcg_out8(s, 0x66); 
@@ -590,7 +594,7 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg 
*args,
         break;
     case 1 | 4:
         /* movswl */
-        tcg_out_modrm_offset(s, 0xbf | P_EXT, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0xbf | P_EXT, data_reg, r0, GUEST_BASE);
         if (bswap) {
             /* rolw $8, data_reg */
             tcg_out8(s, 0x66); 
@@ -603,7 +607,7 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg 
*args,
         break;
     case 2:
         /* movl (r0), data_reg */
-        tcg_out_modrm_offset(s, 0x8b, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0x8b, data_reg, r0, GUEST_BASE);
         if (bswap) {
             /* bswap */
             tcg_out_opc(s, (0xc8 + data_reg) | P_EXT);
@@ -615,17 +619,17 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg 
*args,
             r1 = TCG_REG_EDX;
             if (r1 == data_reg)
                 r1 = TCG_REG_EAX;
-            tcg_out_mov(s, r1, r0);
+            tcg_out_mov(s, r1, GUEST_BASE);
             r0 = r1;
         }
         if (!bswap) {
-            tcg_out_modrm_offset(s, 0x8b, data_reg, r0, 0);
-            tcg_out_modrm_offset(s, 0x8b, data_reg2, r0, 4);
+            tcg_out_modrm_offset(s, 0x8b, data_reg, r0, GUEST_BASE);
+            tcg_out_modrm_offset(s, 0x8b, data_reg2, r0, GUEST_BASE + 4);
         } else {
-            tcg_out_modrm_offset(s, 0x8b, data_reg, r0, 4);
+            tcg_out_modrm_offset(s, 0x8b, data_reg, r0, GUEST_BASE + 4);
             tcg_out_opc(s, (0xc8 + data_reg) | P_EXT);
 
-            tcg_out_modrm_offset(s, 0x8b, data_reg2, r0, 0);
+            tcg_out_modrm_offset(s, 0x8b, data_reg2, r0, GUEST_BASE);
             /* bswap */
             tcg_out_opc(s, (0xc8 + data_reg2) | P_EXT);
         }
@@ -806,7 +810,7 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg 
*args,
     switch(opc) {
     case 0:
         /* movb */
-        tcg_out_modrm_offset(s, 0x88, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0x88, data_reg, r0, GUEST_BASE);
         break;
     case 1:
         if (bswap) {
@@ -818,7 +822,7 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg 
*args,
         }
         /* movw */
         tcg_out8(s, 0x66);
-        tcg_out_modrm_offset(s, 0x89, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0x89, data_reg, r0, GUEST_BASE);
         break;
     case 2:
         if (bswap) {
@@ -828,21 +832,21 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg 
*args,
             data_reg = r1;
         }
         /* movl */
-        tcg_out_modrm_offset(s, 0x89, data_reg, r0, 0);
+        tcg_out_modrm_offset(s, 0x89, data_reg, r0, GUEST_BASE);
         break;
     case 3:
         if (bswap) {
             tcg_out_mov(s, r1, data_reg2);
             /* bswap data_reg */
             tcg_out_opc(s, (0xc8 + r1) | P_EXT);
-            tcg_out_modrm_offset(s, 0x89, r1, r0, 0);
+            tcg_out_modrm_offset(s, 0x89, r1, r0, GUEST_BASE);
             tcg_out_mov(s, r1, data_reg);
             /* bswap data_reg */
             tcg_out_opc(s, (0xc8 + r1) | P_EXT);
-            tcg_out_modrm_offset(s, 0x89, r1, r0, 4);
+            tcg_out_modrm_offset(s, 0x89, r1, r0, GUEST_BASE + 4);
         } else {
-            tcg_out_modrm_offset(s, 0x89, data_reg, r0, 0);
-            tcg_out_modrm_offset(s, 0x89, data_reg2, r0, 4);
+            tcg_out_modrm_offset(s, 0x89, data_reg, r0, GUEST_BASE);
+            tcg_out_modrm_offset(s, 0x89, data_reg2, r0, GUEST_BASE + 4);
         }
         break;
     default:


P.S. BTW revived?

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