Implement fscale

mehfooz09 · Dec 2, 2018 · beaff8d · beaff8d
1 parent cfaef9d
commit beaff8d
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Showing 7 changed files with 27 additions and 7 deletions.
diff --git a/emu/decode.h b/emu/decode.h
@@ -659,6 +659,7 @@ __no_instrument DECODER_RET glue(DECODER_NAME, OP_SIZE)(DECODER_ARGS) {
                     case 0xd970: TRACE("fprem"); FPREM(); break;
                     case 0xd972: TRACE("fsqrt"); FSQRT(); break;
                     case 0xd974: TRACE("frndint"); FRNDINT(); break;
+                    case 0xd975: TRACE("fscale"); FSCALE(); break;
                     case 0xde31: TRACE("fcompp"); FCOM(); FPOP; FPOP; break;
                     case 0xdf40: TRACE("fnstsw ax"); FSTSW(reg_a); break;
                     default: TRACE("undefined"); UNDEFINED;

diff --git a/emu/float80.c b/emu/float80.c
@@ -484,7 +484,7 @@ float80 f80_sqrt(float80 x) {
     // for a rough guess, just cut the exponent by 2
     float80 guess = x;
     guess.exp = bias(unbias(guess.exp) / 2);
-    // now converge on the answer, using what newton's method
+    // now converge on the answer, using newton's method
     float80 old_guess;
     float80 two = f80_from_int(2);
     int i = 0;
@@ -494,3 +494,9 @@ float80 f80_sqrt(float80 x) {
     } while (!f80_eq(guess, old_guess) && i++ < 100);
     return guess;
 }
+
+float80 f80_scale(float80 x, int scale) {
+    if (!f80_is_supported(x) || f80_isnan(x))
+        return F80_NAN;
+    return u128_normalize_round((unsigned __int128) x.signif << 64, unbias(x.exp) + scale, x.sign);
+}
diff --git a/emu/float80.h b/emu/float80.h
@@ -26,9 +26,6 @@ bool f80_iszero(float80 f);
 bool f80_isdenormal(float80 f);
 bool f80_is_supported(float80 f);
 
-float80 f80_neg(float80 f);
-float80 f80_abs(float80 f);
-
 float80 f80_add(float80 a, float80 b);
 float80 f80_sub(float80 a, float80 b);
 float80 f80_mul(float80 a, float80 b);
@@ -40,6 +37,14 @@ bool f80_lt(float80 a, float80 b);
 bool f80_eq(float80 a, float80 b);
 bool f80_uncomparable(float80 a, float80 b);
 
+float80 f80_neg(float80 f);
+float80 f80_abs(float80 f);
+
+float80 f80_log2(float80 x);
+float80 f80_sqrt(float80 x);
+
+float80 f80_scale(float80 x, int scale);
+
 enum f80_rounding_mode {
     round_to_nearest = 0,
     round_down = 1,
@@ -51,7 +56,4 @@ extern __thread enum f80_rounding_mode f80_rounding_mode;
 #define F80_NAN ((float80) {.signif = 0xc000000000000000, .exp = 0x7fff, .sign = 0})
 #define F80_INF ((float80) {.signif = 0x8000000000000000, .exp = 0x7fff, .sign = 0})
 
-float80 f80_log2(float80 x);
-float80 f80_sqrt(float80 x);
-
 #endif
diff --git a/emu/fpu.c b/emu/fpu.c
@@ -84,6 +84,14 @@ void fpu_prem(struct cpu_state *cpu) {
     ST(0) = f80_mod(ST(0), ST(1));
 }
 
+void fpu_scale(struct cpu_state *cpu) {
+    enum f80_rounding_mode old_mode = f80_rounding_mode;
+    f80_rounding_mode = round_chop;
+    int scale = f80_to_int(ST(1));
+    f80_rounding_mode = old_mode;
+    ST(0) = f80_scale(ST(0), scale);
+}
+
 void fpu_rndint(struct cpu_state *cpu) {
     if (f80_isinf(ST(0)) || f80_isnan(ST(0)))
         return;

diff --git a/emu/fpu.h b/emu/fpu.h
@@ -47,6 +47,7 @@ void fpu_ldm80(struct cpu_state *cpu, float80 *f);
 
 void fpu_prem(struct cpu_state *cpu);
 void fpu_rndint(struct cpu_state *cpu);
+void fpu_scale(struct cpu_state *cpu);
 void fpu_abs(struct cpu_state *cpu);
 void fpu_chs(struct cpu_state *cpu);
 void fpu_sqrt(struct cpu_state *cpu);

diff --git a/emu/interp/fpu.h b/emu/interp/fpu.h
@@ -80,6 +80,7 @@
     ST(0) = f80_mod(ST(0), ST(1))
 
 #define FRNDINT() UNDEFINED
+#define FSCALE() UNDEFINED
 #define FYL2X() UNDEFINED
 #define F2XM1() UNDEFINED
 #define FSQRT() UNDEFINED

diff --git a/jit/gen.c b/jit/gen.c
@@ -364,6 +364,7 @@ void helper_rdtsc(struct cpu_state *cpu);
 #define FLDC(what) hh(fpu_ldc, fconst_##what)
 #define FPREM() h(fpu_prem)
 #define FRNDINT() h(fpu_rndint)
+#define FSCALE() h(fpu_scale)
 #define FSQRT() h(fpu_sqrt)
 #define FYL2X() h(fpu_yl2x)
 #define F2XM1() h(fpu_2xm1)