Index: compiler/x86/rax86.pas
===================================================================
--- compiler/x86/rax86.pas	(revision 47011)
+++ compiler/x86/rax86.pas	(working copy)
@@ -1402,6 +1402,44 @@
 
 
 procedure Tx86Instruction.SetInstructionOpsize;
+
+  function CheckSSEAVX: Boolean;
+    begin
+      Result := False;
+
+      if not MemRefInfo(opcode).ExistsSSEAVX then
+        Exit;
+
+      { This check also covers MMX instructions that move data to and from
+        32-bit and 64-bit registers or memory, since such instructions are
+        replicated in SSE2 for use with XMM registers }
+      if tx86operand(operands[1]).opsize in [S_B,S_W,S_L,S_Q] then
+        begin
+          opsize := S_NO;
+          Exit(True);
+        end;
+
+      if (tx86operand(operands[1]).opsize <> S_NO) and (operands[1].opr.typ = OPR_REFERENCE) then
+        begin
+          { Memory sizes of 64 bits and under are handled above }
+          opsize:=tx86operand(operands[1]).opsize;
+          Exit(True);
+        end;
+
+      { If the source operand is larger than the destination (e.g.
+        "VCVTTPD2DQ XMM0, YMM1" in Intel notation), use the source operand }
+      if ((tx86operand(operands[1]).opsize = S_YMM) and (tx86operand(operands[2]).opsize = S_XMM)) or
+        (tx86operand(operands[1]).opsize = S_ZMM) and (tx86operand(operands[2]).opsize = S_XMM) or
+        (tx86operand(operands[1]).opsize = S_ZMM) and (tx86operand(operands[2]).opsize = S_YMM) then
+        begin
+          opsize:=tx86operand(operands[1]).opsize;
+          Exit(True);
+        end;
+
+      { If none of the conditions are met, this function returns False and the
+        opsize is set to the last operand's opsize }
+    end;
+
 begin
   if opsize<>S_NO then
    exit;
@@ -1466,33 +1504,22 @@
                   ;
               end;
             end;
-          A_MOVSS,
-          A_VMOVSS,
-          A_MOVD : { movd is a move from a mmx register to a
-                     32 bit register or memory, so no opsize is correct here PM }
-            exit;
-          A_MOVQ :
-            opsize:=S_IQ;
-          A_CVTSI2SS,
-          A_CVTSI2SD,
           A_OUT :
             opsize:=tx86operand(operands[1]).opsize;
           else
-            opsize:=tx86operand(operands[2]).opsize;
+            begin
+              if not CheckSSEAVX then
+                opsize:=tx86operand(operands[2]).opsize;
+            end;
         end;
       end;
     3 :
       begin
-        case opcode of
-          A_VCVTSI2SS,
-          A_VCVTSI2SD:
-            opsize:=tx86operand(operands[1]).opsize;
-        else
-          opsize:=tx86operand(operands[ops]).opsize;
-        end;
+        if not CheckSSEAVX then
+          opsize:=tx86operand(operands[3]).opsize;
       end;
-    4 :
-        opsize:=tx86operand(operands[ops]).opsize;
+    else
+      opsize:=tx86operand(operands[ops]).opsize;
 
   end;
 end;