FPU: Implement zero divide fault

src/rust/cpu2/fpu.rs

@@ -3,6 +3,7 @@ use std::mem::transmute;
 use cpu2::cpu::*;
 use cpu2::global_pointers::*;
 use paging::OrPageFault;
+use std::f64;
 
 pub fn round(x: f64) -> f64 { x.round() }
 pub fn floor(x: f64) -> f64 { x.floor() }
@@ -23,6 +24,7 @@ const FPU_C3: i32 = 0x4000;
 const FPU_RESULT_FLAGS: i32 = FPU_C0 | FPU_C1 | FPU_C2 | FPU_C3;
 const INDEFINITE_NAN: f64 = ::std::f64::NAN;
 const FPU_EX_I: i32 = 1 << 0;
+const FPU_EX_Z: i32 = 1 << 2;
 const FPU_EX_SF: i32 = 1 << 6;
 const TWO_POW_63: f64 = 0x8000000000000000u64 as f64;
 
@@ -89,6 +91,12 @@ pub unsafe fn fpu_stack_fault() {
     *fpu_status_word |= FPU_EX_SF | FPU_EX_I;
 }
 
+#[no_mangle]
+pub unsafe fn fpu_zero_fault() {
+    // TODO: Interrupt
+    *fpu_status_word |= FPU_EX_Z;
+}
+
 #[no_mangle]
 pub unsafe fn fpu_sti_empty(mut i: i32) -> bool {
     dbg_assert!(i >= 0 && i < 8);
@@ -305,11 +313,17 @@ pub unsafe fn fpu_fcomp(val: f64) {
 #[no_mangle]
 pub unsafe fn fpu_fdiv(target_index: i32, val: f64) {
     let st0: f64 = fpu_get_st0();
+    if val == 0.0 {
+        fpu_zero_fault();
+    }
     fpu_write_st(*fpu_stack_ptr as i32 + target_index & 7, st0 / val);
 }
 #[no_mangle]
 pub unsafe fn fpu_fdivr(target_index: i32, val: f64) {
     let st0: f64 = fpu_get_st0();
+    if st0 == 0.0 {
+        fpu_zero_fault();
+    }
     fpu_write_st(*fpu_stack_ptr as i32 + target_index & 7, val / st0);
 }
 #[no_mangle]
@@ -762,15 +776,37 @@ pub unsafe fn fpu_fxch(i: i32) {
     fpu_write_st(*fpu_stack_ptr as i32 + i & 7, fpu_get_st0());
     fpu_write_st(*fpu_stack_ptr as i32, sti);
 }
-#[no_mangle]
-pub unsafe fn fpu_fxtract() {
-    let mut f = FloatParts::of_f64(fpu_get_st0());
+pub unsafe fn fpu_fyl2x() {
+    let st0 = fpu_get_st0();
+    if st0 < 0.0 {
+        fpu_invalid_arithmetic();
+    }
+    else if st0 == 0.0 {
+        fpu_zero_fault();
+    }
     fpu_write_st(
-        *fpu_stack_ptr as i32,
-        f.exponent as f64 - F64_EXPONENT_BIAS as f64,
+        *fpu_stack_ptr as i32 + 1 & 7,
+        fpu_get_sti(1) * st0.ln() / M_LN2,
     );
-    f.exponent = 0x3FF;
-    fpu_push(f.to_f64());
+    fpu_pop();
+}
+#[no_mangle]
+pub unsafe fn fpu_fxtract() {
+    let st0 = fpu_get_st0();
+    if st0 == 0.0 {
+        fpu_zero_fault();
+        fpu_write_st(*fpu_stack_ptr as i32, f64::NEG_INFINITY);
+        fpu_push(st0);
+    }
+    else {
+        let mut f = FloatParts::of_f64(st0);
+        fpu_write_st(
+            *fpu_stack_ptr as i32,
+            f.exponent as f64 - F64_EXPONENT_BIAS as f64,
+        );
+        f.exponent = 0x3FF;
+        fpu_push(f.to_f64());
+    }
 }
 #[no_mangle]
 pub unsafe fn fwait() {

src/rust/cpu2/instructions.rs

@@ -3698,14 +3698,7 @@ pub unsafe fn instr_D9_6_reg(r: i32) {
         },
         1 => {
             // fyl2x
-            if st0 < 0.0 {
-                fpu_invalid_arithmetic();
-            }
-            fpu_write_st(
-                *fpu_stack_ptr as i32 + 1 & 7,
-                fpu_get_sti(1) * st0.ln() / M_LN2,
-            );
-            fpu_pop();
+            fpu_fyl2x();
         },
         2 => {
             // fptan

tests/nasm/fdiv-zero.asm

@@ -0,0 +1,14 @@
+global _start
+
+section .data
+	align 16
+
+%include "header.inc"
+
+    push 1234
+    fild dword [esp]
+    push 0
+    fild dword [esp]
+    fdiv
+
+%include "footer.inc"

tests/nasm/fxtract-zero.asm

@@ -0,0 +1,12 @@
+global _start
+
+section .data
+	align 16
+
+%include "header.inc"
+
+    push 0
+    fild dword [esp]
+    fxtract
+
+%include "footer.inc"

tests/nasm/fyl2x-zero.asm

@@ -0,0 +1,14 @@
+global _start
+
+section .data
+	align 16
+
+%include "header.inc"
+
+    push 1234
+    fild dword [esp]
+    push 0
+    fild dword [esp]
+    fyl2x
+
+%include "footer.inc"