Implement fninit

asbestos/gen.c

@@ -412,6 +412,7 @@ void helper_rdtsc(struct cpu_state *cpu);
 #define FLDENV(val,z) h_write(fpu_ldenv, z)
 #define FSAVE(val,z) h_write(fpu_save, z)
 #define FRESTORE(val,z) h_write(fpu_restore, z)
+#define FINIT() h(fpu_init)
 #define FCLEX() h(fpu_clex)
 #define FPOP h(fpu_pop)
 #define FINCSTP() h(fpu_incstp)

emu/decode.h

@@ -1084,6 +1084,7 @@ __no_instrument DECODER_RET glue(DECODER_NAME, OP_SIZE)(DECODER_ARGS) {
                     case 0xd976: TRACE("fsin"); FSIN(); break;
                     case 0xd977: TRACE("fcos"); FCOS(); break;
                     case 0xdb42: TRACE("fnclex"); FCLEX(); break;
+                    case 0xdb43: TRACE("fninit"); FINIT(); break;
                     case 0xde31: TRACE("fcompp"); FCOM(); FPOP; FPOP; break;
                     case 0xdf40: TRACE("fnstsw ax"); FSTSW(reg_a); break;
                     default: TRACE("undefined"); UNDEFINED;

emu/fpu.c

@@ -377,6 +377,18 @@ void fpu_restore32(struct cpu_state *cpu, struct fpu_state32 *state) {
         memcpy(&ST(i), state->regs[i], 10);
 }
 
+// FNINIT: control word back to 0x037f (all exceptions masked, round to
+// nearest, extended precision) and the status word cleared. Clearing fsw also
+// resets TOP, since TOP is a field of it, which is what empties the register
+// stack; there is no tag word to write because we do not model one. The
+// control word changing means the live rounding mode has to follow it, the
+// same way fldcw does.
+void fpu_init(struct cpu_state *cpu) {
+    cpu->fcw = 0x037f;
+    cpu->fsw = 0;
+    f80_rounding_mode = cpu->rc;
+}
+
 void fpu_clex(struct cpu_state *cpu) {
     cpu->pe = cpu->ue = cpu->oe = cpu->ze = cpu->de = cpu->ie = cpu->es = cpu->sf = cpu->b = 0;
 }

emu/fpu.h

@@ -119,6 +119,7 @@ void fpu_stenv32(struct cpu_state *cpu, struct fpu_env32 *env);
 void fpu_ldenv32(struct cpu_state *cpu, struct fpu_env32 *env);
 void fpu_save32(struct cpu_state *cpu, struct fpu_state32 *state);
 void fpu_restore32(struct cpu_state *cpu, struct fpu_state32 *state);
+void fpu_init(struct cpu_state *cpu);
 void fpu_clex(struct cpu_state *cpu);
 
 #endif