diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 3a1973de13d..06dcb31fb1d 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -25949,7 +25949,7 @@
   "TARGET_RDRND"
   "rdrand\t%0"
   [(set_attr "type" "other")
-   (set_attr "prefix_extra" "1")])
+   (set_attr "prefix_0f" "1")])
 
 (define_insn "@rdseed<mode>"
   [(set (match_operand:SWI248 0 "register_operand" "=r")
@@ -25959,7 +25959,7 @@
   "TARGET_RDSEED"
   "rdseed\t%0"
   [(set_attr "type" "other")
-   (set_attr "prefix_extra" "1")])
+   (set_attr "prefix_0f" "1")])
 
 (define_expand "pause"
   [(set (match_dup 0)
diff --git a/gcc/config/i386/mmx.md b/gcc/config/i386/mmx.md
index 2713cdb112e..7b7ff68e2a1 100644
--- a/gcc/config/i386/mmx.md
+++ b/gcc/config/i386/mmx.md
@@ -2483,7 +2483,7 @@
    vp<maxmin_int><mmxvecsize>\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "sseiadd")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,vex")
    (set_attr "mode" "TI")])
 
@@ -2532,7 +2532,7 @@
    vp<maxmin_int>b\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "sseiadd")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,vex")
    (set_attr "mode" "TI")])
 
@@ -2561,7 +2561,7 @@
    vp<maxmin_int><mmxvecsize>\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "sseiadd")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,vex")
    (set_attr "mode" "TI")])
 
@@ -2623,7 +2623,7 @@
    vp<maxmin_int>w\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "sseiadd")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,vex")
    (set_attr "mode" "TI")])
 
diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md
index 9513bd26946..37acc11034f 100644
--- a/gcc/config/i386/sse.md
+++ b/gcc/config/i386/sse.md
@@ -11064,7 +11064,7 @@
 		   (const_string "1")
 		   (const_string "*")))
    (set (attr "prefix_extra")
-     (if_then_else (eq_attr "alternative" "5,6,7,8,9")
+     (if_then_else (eq_attr "alternative" "5,6,9")
 		   (const_string "1")
 		   (const_string "*")))
    (set (attr "length_immediate")
@@ -16753,7 +16753,7 @@
    vp<maxmin_int><ssemodesuffix>\t{%2, %1, %0<mask_operand3>|%0<mask_operand3>, %1, %2}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "sseiadd")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,vex")
    (set_attr "mode" "TI")])
 
@@ -16871,7 +16871,10 @@
   "TARGET_AVX2 && !(MEM_P (operands[1]) && MEM_P (operands[2]))"
   "vpcmpeq<ssemodesuffix>\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "type" "ssecmp")
-   (set_attr "prefix_extra" "1")
+   (set (attr "prefix_extra")
+     (if_then_else (eq (const_string "<MODE>mode") (const_string "V4DImode"))
+		   (const_string "1")
+		   (const_string "*")))
    (set_attr "prefix" "vex")
    (set_attr "mode" "OI")])
 
@@ -17106,7 +17109,10 @@
   "TARGET_AVX2"
   "vpcmpgt<ssemodesuffix>\t{%2, %1, %0|%0, %1, %2}"
   [(set_attr "type" "ssecmp")
-   (set_attr "prefix_extra" "1")
+   (set (attr "prefix_extra")
+     (if_then_else (eq (const_string "<MODE>mode") (const_string "V4DImode"))
+		   (const_string "1")
+		   (const_string "*")))
    (set_attr "prefix" "vex")
    (set_attr "mode" "OI")])
 
@@ -18901,7 +18907,7 @@
        (const_string "*")))
    (set (attr "prefix_extra")
      (if_then_else
-       (and (not (match_test "TARGET_AVX"))
+       (ior (eq_attr "prefix" "evex")
 	    (match_test "GET_MODE_NUNITS (<MODE>mode) == 8"))
        (const_string "*")
        (const_string "1")))
@@ -20062,8 +20068,7 @@
    (set_attr "prefix_data16" "1")
    (set (attr "prefix_extra")
      (if_then_else
-       (and (eq_attr "alternative" "0,2")
-	    (eq (const_string "<MODE>mode") (const_string "V8HImode")))
+       (eq (const_string "<MODE>mode") (const_string "V8HImode"))
        (const_string "*")
        (const_string "1")))
    (set_attr "length_immediate" "1")
@@ -22407,7 +22412,7 @@
   "%vmovntdqa\t{%1, %0|%0, %1}"
   [(set_attr "isa" "noavx,noavx,avx")
    (set_attr "type" "ssemov")
-   (set_attr "prefix_extra" "1,1,*")
+   (set_attr "prefix_extra" "1")
    (set_attr "prefix" "orig,orig,maybe_evex")
    (set_attr "mode" "<sseinsnmode>")])