CPU: Copy entire value for zero shift cases

Shortcut, and avoids tainting the Z.

src/core/cpu_pgxp.cpp

@@ -1617,8 +1617,15 @@ void CPU::PGXP::CPU_SLLV(Instruction instr, u32 rtVal, u32 rsVal)
 
 ALWAYS_INLINE_RELEASE void CPU::PGXP::CPU_SRx(Instruction instr, u32 rtVal, u32 sh, bool sign, bool is_variable)
 {
-  const u32 rdVal = sign ? static_cast<u32>(static_cast<s32>(rtVal) >> sh) : (rtVal >> sh);
   PGXPValue& prtVal = ValidateAndGetRtValue(instr, rtVal);
+  PGXPValue& prdVal = GetRdValue(instr);
+  if (sh == 0)
+  {
+    prdVal = prtVal;
+    return;
+  }
+
+  const u32 rdVal = sign ? static_cast<u32>(static_cast<s32>(rtVal) >> sh) : (rtVal >> sh);
 
   double x = prtVal.x;
   double y = sign ? prtVal.y : f16Unsign(prtVal.y);
@@ -1658,7 +1665,6 @@ ALWAYS_INLINE_RELEASE void CPU::PGXP::CPU_SRx(Instruction instr, u32 rtVal, u32
   else
     y = y / static_cast<double>(1 << sh);
 
-  PGXPValue& prdVal = GetRdValue(instr);
 
   // Use low precision/rounded values when we're not shifting an entire component,
   // and it's not originally from a 3D value. Too many false positives in P2/etc.