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Pre-calculate pow table for FXTRACT instruction

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This commit is contained in:
Cacodemon345
2025-03-20 21:52:48 +06:00
parent 00c97dac1c
commit a9c97abfb6
4 changed files with 14 additions and 1 deletions
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8
src/86box.c
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@@ -32,6 +32,7 @@
#include <wchar.h> #include <wchar.h>
#include <stdatomic.h> #include <stdatomic.h>
#include <unistd.h> #include <unistd.h>
#include <math.h>
#ifndef _WIN32 #ifndef _WIN32
# include <pwd.h> # include <pwd.h>
@@ -233,6 +234,8 @@ extern int CPUID;
extern int output; extern int output;
int atfullspeed; int atfullspeed;
extern double exp_pow_table[0x800];
char exe_path[2048]; /* path (dir) of executable */ char exe_path[2048]; /* path (dir) of executable */
char usr_path[1024]; /* path (dir) of user data */ char usr_path[1024]; /* path (dir) of user data */
char cfg_path[1024]; /* full path of config file */ char cfg_path[1024]; /* full path of config file */
@@ -1086,6 +1089,11 @@ pc_init_modules(void)
machine_status_init(); machine_status_init();
for (c = 0; c <= 0x7ff; c++) {
int64_t exp = c - 1023; /* 1023 = BIAS64 */
exp_pow_table[c] = pow(2.0, (double) exp);
}
if (do_nothing) { if (do_nothing) {
do_nothing = 0; do_nothing = 0;
exit(-1); exit(-1);

3
src/cpu/cpu.c
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@@ -287,6 +287,9 @@ uint8_t reg_30 = 0x00;
uint8_t arr[24] = { 0 }; uint8_t arr[24] = { 0 };
uint8_t rcr[8] = { 0 }; uint8_t rcr[8] = { 0 };
/* Table for FXTRACT. */
double exp_pow_table[0x800];
static int cyrix_addr; static int cyrix_addr;
static void cpu_write(uint16_t addr, uint8_t val, void *priv); static void cpu_write(uint16_t addr, uint8_t val, void *priv);

2
src/cpu/x87_ops.h
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@@ -36,6 +36,8 @@ extern void fpu_log(const char *fmt, ...);
# endif # endif
#endif #endif
extern double exp_pow_table[0x800];
static int rounding_modes[4] = { FE_TONEAREST, FE_DOWNWARD, FE_UPWARD, FE_TOWARDZERO }; static int rounding_modes[4] = { FE_TONEAREST, FE_DOWNWARD, FE_UPWARD, FE_TOWARDZERO };
#define ST(x) cpu_state.ST[((cpu_state.TOP + (x)) & 7)] #define ST(x) cpu_state.ST[((cpu_state.TOP + (x)) & 7)]

2
src/cpu/x87_ops_misc.h
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@@ -46,7 +46,7 @@ opFXTRACT(UNUSED(uint32_t fetchdat))
test.eind.d = ST(0); test.eind.d = ST(0);
exp80 = test.eind.ll & 0x7ff0000000000000LL; exp80 = test.eind.ll & 0x7ff0000000000000LL;
exp80final = (exp80 >> 52) - BIAS64; exp80final = (exp80 >> 52) - BIAS64;
mant = test.eind.d / (pow(2.0, (double) exp80final)); mant = test.eind.d / exp_pow_table[exp80 >> 52];
ST(0) = (double) exp80final; ST(0) = (double) exp80final;
FP_TAG_VALID; FP_TAG_VALID;
x87_push(mant); x87_push(mant);