Changeset 99994 in vbox

Timestamp:

May 26, 2023 10:09:30 PM (18 months ago)

Author:

vboxsync

Message:

VMM/IEM: Allow setting the FCW.IC bit (discontinued with the 387) as intel CPU (at least) still allows this on the 10980xe. ASSUME the FPU ignores it and the sign bit of infinity. bugref:10464

File:

• trunk/src/VBox/VMM/VMMAll/IEMAllCImpl.cpp (modified) (4 diffs)

trunk/src/VBox/VMM/VMMAll/IEMAllCImpl.cpp

@@ -8739 +8739 @@
     }
 
-    pDst->FCW &= ~X86_FCW_ZERO_MASK;
+    pDst->FCW &= ~X86_FCW_ZERO_MASK | X86_FCW_IC_MASK; /* Intel 10980xe allows setting the IC bit. Win 3.11 CALC.EXE sets it. */
     iemFpuRecalcExceptionStatus(pDst);
 
@@ -9021 +9021 @@
             }
 
-            pDst->FCW &= ~X86_FCW_ZERO_MASK;
+            pDst->FCW &= ~X86_FCW_ZERO_MASK | X86_FCW_IC_MASK; /* Intel 10980xe allows setting the IC bit. Win 3.11 CALC.EXE sets it. */
             iemFpuRecalcExceptionStatus(pDst);
 
@@ -9376 +9376 @@
     uint16_t const fOldFsw = pDstX87->FSW;
 #endif
-    pDstX87->FCW &= ~X86_FCW_ZERO_MASK;
+    pDstX87->FCW &= ~X86_FCW_ZERO_MASK | X86_FCW_IC_MASK; /* Intel 10980xe allows setting the IC bit. Win 3.11 CALC.EXE sets it. */
     iemFpuRecalcExceptionStatus(pDstX87);
 #ifdef LOG_ENABLED
@@ -9563 +9563 @@
      *        according to FSW. (This is what is currently implemented.) */
     PX86FXSTATE pFpuCtx = &pVCpu->cpum.GstCtx.XState.x87;
-    pFpuCtx->FCW = u16Fcw & ~X86_FCW_ZERO_MASK;
+    pFpuCtx->FCW = u16Fcw & (~X86_FCW_ZERO_MASK | X86_FCW_IC_MASK); /* Intel 10980xe allows setting the IC bit. Win 3.11 CALC.EXE sets it. */
 #ifdef LOG_ENABLED
     uint16_t fOldFsw = pFpuCtx->FSW;