From 20432122de2634dfa8da79f97a3695fce6c97498 Mon Sep 17 00:00:00 2001
From: ptitSeb <sebastien.chev@gmail.com>
Date: Tue, 3 Dec 2024 14:36:23 +0100
Subject: [PATCH] [INTERPRETER] Fixed D9 F4 opcode ([DYNAREC] too) (backported
 from box64)

---
 src/dynarec/dynarec_arm_functions.c | 18 ++++++++++++++----
 src/emu/x86rund9.c                  | 15 +++++++++++++--
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/dynarec/dynarec_arm_functions.c b/src/dynarec/dynarec_arm_functions.c
index fe1a6300..c1fe888b 100755
--- a/src/dynarec/dynarec_arm_functions.c
+++ b/src/dynarec/dynarec_arm_functions.c
@@ -62,10 +62,20 @@ void arm_fpatan(x86emu_t* emu)
 }
 void arm_fxtract(x86emu_t* emu)
 {
-    int32_t tmp32s = (ST1.q&0x7ff0000000000000LL)>>52;
-    tmp32s -= 1023;
-    ST1.d /= exp2(tmp32s);
-    ST0.d = tmp32s;
+    int tmp32s;
+    if(isnan(ST1.d)) {
+        ST0.d = ST1.d;
+    } else if(isinf(ST1.d)) {
+        ST0.d = ST1.d;
+        ST1.d = INFINITY;
+    } else if(ST1.d==0.0) {
+        ST0.d = ST1.d;
+        ST1.d = -INFINITY;
+    } else {
+        // LD80bits doesn't have implicit "1" bit, so need to adjust for that
+        ST0.d = frexp(ST1.d, &tmp32s)*2;
+        ST1.d = tmp32s-1;
+    }
 }
 void arm_fprem(x86emu_t* emu)
 {
diff --git a/src/emu/x86rund9.c b/src/emu/x86rund9.c
index 9567c0e2..8c31d618 100755
--- a/src/emu/x86rund9.c
+++ b/src/emu/x86rund9.c
@@ -144,9 +144,20 @@ uintptr_t RunD9(x86emu_t *emu, uintptr_t addr)
             emu->sw.f.F87_C1 = 0;
             break;
         case 0xF4:  /* FXTRACT */
-            ST0.d = frexp(ST0.d, &tmp32s);
             fpu_do_push(emu);
-            ST0.d = tmp32s;
+            if(isnan(ST1.d)) {
+                ST0.d = ST1.d;
+            } else if(isinf(ST1.d)) {
+                ST0.d = ST1.d;
+                ST1.d = INFINITY;
+            } else if(ST1.d==0.0) {
+                ST0.d = ST1.d;
+                ST1.d = -INFINITY;
+            } else {
+                // LD80bits doesn't have implicit "1" bit, so need to adjust for that
+                ST0.d = frexp(ST1.d, &tmp32s)*2;
+                ST1.d = tmp32s-1;
+            }
             // C1 set only if stack under/overflow occurs
             break;