[release/9.0] Fix Issue #105820 (#106656)

* Check for writing sign flag for skipping test condition in compare to zero

* Only skip test instruction in case Writes_PF, Writes ZF, WritesSF, ResetsCF and ResetsOF are true

---------

Co-authored-by: Khushal Modi <[email protected]>
Co-authored-by: Jeff Schwartz <[email protected]>

src/coreclr/jit/emitxarch.cpp

@@ -355,6 +355,22 @@ bool emitter::DoesWriteZeroFlag(instruction ins)
     return (flags & Writes_ZF) != 0;
 }
 
+//------------------------------------------------------------------------
+// DoesWriteParityFlag: check if the instruction write the
+//     PF flag.
+//
+// Arguments:
+//    ins - instruction to test
+//
+// Return Value:
+//    true if instruction writes the PF flag, false otherwise.
+//
+bool emitter::DoesWriteParityFlag(instruction ins)
+{
+    insFlags flags = CodeGenInterface::instInfo[ins];
+    return (flags & Writes_PF) != 0;
+}
+
 //------------------------------------------------------------------------
 // DoesWriteSignFlag: check if the instruction writes the
 //     SF flag.
@@ -979,7 +995,8 @@ bool emitter::AreFlagsSetToZeroCmp(regNumber reg, emitAttr opSize, GenCondition
     // Certain instruction like and, or and xor modifies exactly same flags
     // as "test" instruction.
     // They reset OF and CF to 0 and modifies SF, ZF and PF.
-    if (DoesResetOverflowAndCarryFlags(lastIns))
+    if (DoesResetOverflowAndCarryFlags(lastIns) && DoesWriteSignFlag(lastIns) && DoesWriteZeroFlag(lastIns) &&
+        DoesWriteParityFlag(lastIns))
     {
         return id->idOpSize() == opSize;
     }

src/coreclr/jit/emitxarch.h

@@ -484,6 +484,7 @@ bool        IsThreeOperandAVXInstruction(instruction ins) const;
 static bool HasRegularWideForm(instruction ins);
 static bool HasRegularWideImmediateForm(instruction ins);
 static bool DoesWriteZeroFlag(instruction ins);
+static bool DoesWriteParityFlag(instruction ins);
 static bool DoesWriteSignFlag(instruction ins);
 static bool DoesResetOverflowAndCarryFlags(instruction ins);
 bool        IsFlagsAlwaysModified(instrDesc* id);