# Node ID c76b781104905fd4c9bb39a9876d7dfa92200026
# Parent  9bddacd7af81567eec633c64cf15a3acd996c795
diff --git a/src/arch/x86/isa/microops/regop.isa b/src/arch/x86/isa/microops/regop.isa
--- a/src/arch/x86/isa/microops/regop.isa
+++ b/src/arch/x86/isa/microops/regop.isa
@@ -580,15 +580,17 @@
 
         code = '''
             ProdLow = psrc1 * op2;
-            int halfSize = (dataSize * 8) / 2;
-            uint64_t shifter = (ULL(1) << halfSize);
-            uint64_t psrc1_h = psrc1 / shifter;
-            uint64_t psrc1_l = psrc1 & mask(halfSize);
-            uint64_t psrc2_h = (op2 / shifter) & mask(halfSize);
-            uint64_t psrc2_l = op2 & mask(halfSize);
-            ProdHi = ((psrc1_l * psrc2_h + psrc1_h * psrc2_l +
-                      ((psrc1_l * psrc2_l) / shifter)) / shifter) +
-                     psrc1_h * psrc2_h;
+            int shifter = (dataSize * 8) / 2;
+            uint64_t psrc1_h = (psrc1 >> shifter) & mask(shifter);
+            uint64_t psrc1_l = psrc1 & mask(shifter);
+            uint64_t psrc2_h = (op2 >> shifter) & mask(shifter);
+            uint64_t psrc2_l = op2 & mask(shifter);
+
+            ProdHi = psrc1_h * psrc2_h + ((psrc1_h * psrc2_l) >> shifter)
+                     + ((psrc1_l * psrc2_h) >> shifter)
+                     + ((((psrc1_l * psrc2_h) & 0xffffffff)
+                     + ((psrc1_h * psrc2_l) & 0xffffffff)
+                     + ((psrc1_l * psrc2_l) >> shifter)) >> shifter);
             '''
         flag_code = '''
             if (ProdHi) {