[Xen-devel] [PATCH] ioemu: save 3MB of ioport tables (on 64bit machines)

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>]

ioemu: save 3MB of ioport tables (on 64bit machines)
by keeping then initialized to NULL and check for it in the handlers.

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>

---
This is a bargain between memory usage and CPU usage.  Checking for
NULL and setting a default value is just a matter of test;jz;mov, it is
probably worth the saved 3MB.

diff -r 1104e9a108c2 tools/ioemu/vl.c
--- a/tools/ioemu/vl.c  Mon Feb 11 11:50:26 2008 +0000
+++ b/tools/ioemu/vl.c  Mon Feb 11 12:07:27 2008 +0000
@@ -227,17 +227,29 @@ uint32_t default_ioport_readw(void *opaq
 uint32_t default_ioport_readw(void *opaque, uint32_t address)
 {
     uint32_t data;
-    data = ioport_read_table[0][address](ioport_opaque[address], address);
+    IOPortReadFunc *func = ioport_read_table[0][address];
+    if (!func)
+           func = default_ioport_readb;
+    data = func(ioport_opaque[address], address);
     address = (address + 1) & (MAX_IOPORTS - 1);
-    data |= ioport_read_table[0][address](ioport_opaque[address], address) << 
8;
+    func = ioport_read_table[0][address];
+    if (!func)
+           func = default_ioport_readb;
+    data |= func(ioport_opaque[address], address) << 8;
     return data;
 }
 
 void default_ioport_writew(void *opaque, uint32_t address, uint32_t data)
 {
-    ioport_write_table[0][address](ioport_opaque[address], address, data & 
0xff);
+    IOPortWriteFunc *func = ioport_write_table[0][address];
+    if (!func)
+           func = default_ioport_writeb;
+    func(ioport_opaque[address], address, data & 0xff);
     address = (address + 1) & (MAX_IOPORTS - 1);
-    ioport_write_table[0][address](ioport_opaque[address], address, (data >> 
8) & 0xff);
+    func = ioport_write_table[0][address];
+    if (!func)
+           func = default_ioport_writeb;
+    func(ioport_opaque[address], address, (data >> 8) & 0xff);
 }
 
 uint32_t default_ioport_readl(void *opaque, uint32_t address)
@@ -257,16 +269,6 @@ void default_ioport_writel(void *opaque,
 
 void init_ioports(void)
 {
-    int i;
-
-    for(i = 0; i < MAX_IOPORTS; i++) {
-        ioport_read_table[0][i] = default_ioport_readb;
-        ioport_write_table[0][i] = default_ioport_writeb;
-        ioport_read_table[1][i] = default_ioport_readw;
-        ioport_write_table[1][i] = default_ioport_writew;
-        ioport_read_table[2][i] = default_ioport_readl;
-        ioport_write_table[2][i] = default_ioport_writel;
-    }
 }
 
 /* size is the word size in byte */
@@ -338,11 +340,14 @@ void isa_unassign_ioport(int start, int 
 
 void cpu_outb(CPUState *env, int addr, int val)
 {
+    IOPortWriteFunc *func = ioport_write_table[0][addr];
+    if (!func)
+           func = default_ioport_writeb;
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "outb: %04x %02x\n", addr, val);
 #endif    
-    ioport_write_table[0][addr](ioport_opaque[addr], addr, val);
+    func(ioport_opaque[addr], addr, val);
 #ifdef USE_KQEMU
     if (env)
         env->last_io_time = cpu_get_time_fast();
@@ -351,11 +356,14 @@ void cpu_outb(CPUState *env, int addr, i
 
 void cpu_outw(CPUState *env, int addr, int val)
 {
+    IOPortWriteFunc *func = ioport_write_table[1][addr];
+    if (!func)
+           func = default_ioport_writew;
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "outw: %04x %04x\n", addr, val);
 #endif    
-    ioport_write_table[1][addr](ioport_opaque[addr], addr, val);
+    func(ioport_opaque[addr], addr, val);
 #ifdef USE_KQEMU
     if (env)
         env->last_io_time = cpu_get_time_fast();
@@ -364,11 +372,14 @@ void cpu_outw(CPUState *env, int addr, i
 
 void cpu_outl(CPUState *env, int addr, int val)
 {
+    IOPortWriteFunc *func = ioport_write_table[2][addr];
+    if (!func)
+           func = default_ioport_writel;
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "outl: %04x %08x\n", addr, val);
 #endif
-    ioport_write_table[2][addr](ioport_opaque[addr], addr, val);
+    func(ioport_opaque[addr], addr, val);
 #ifdef USE_KQEMU
     if (env)
         env->last_io_time = cpu_get_time_fast();
@@ -378,7 +389,10 @@ int cpu_inb(CPUState *env, int addr)
 int cpu_inb(CPUState *env, int addr)
 {
     int val;
-    val = ioport_read_table[0][addr](ioport_opaque[addr], addr);
+    IOPortReadFunc *func = ioport_read_table[0][addr];
+    if (!func)
+           func = default_ioport_readb;
+    val = func(ioport_opaque[addr], addr);
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "inb : %04x %02x\n", addr, val);
@@ -393,7 +407,10 @@ int cpu_inw(CPUState *env, int addr)
 int cpu_inw(CPUState *env, int addr)
 {
     int val;
-    val = ioport_read_table[1][addr](ioport_opaque[addr], addr);
+    IOPortReadFunc *func = ioport_read_table[1][addr];
+    if (!func)
+           func = default_ioport_readw;
+    val = func(ioport_opaque[addr], addr);
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "inw : %04x %04x\n", addr, val);
@@ -408,7 +425,10 @@ int cpu_inl(CPUState *env, int addr)
 int cpu_inl(CPUState *env, int addr)
 {
     int val;
-    val = ioport_read_table[2][addr](ioport_opaque[addr], addr);
+    IOPortReadFunc *func = ioport_read_table[2][addr];
+    if (!func)
+           func = default_ioport_readl;
+    val = func(ioport_opaque[addr], addr);
 #ifdef DEBUG_IOPORT
     if (loglevel & CPU_LOG_IOPORT)
         fprintf(logfile, "inl : %04x %08x\n", addr, val);

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