diff --git a/tz/avx_amd64.s b/tz/avx_amd64.s
index 7c867b7..3648741 100644
--- a/tz/avx_amd64.s
+++ b/tz/avx_amd64.s
@@ -6,22 +6,15 @@
     VPSLLQ $1, FROM, TO \
     VPALIGNR $8, TO, FROM, R2 \
     VPSRLQ $63, R2, R2 \
-    VMOVDQU ·x127x63(SB), R3 \
-    VANDPD TO, R3, R3 \
+    VANDPD TO, X14, R3 \
     VPUNPCKHQDQ R3, R3, R3 \
     VXORPD R2, TO, TO \
     VXORPD R3, TO, TO
 
-#define mask(bit, src, tmp, to1, to2) \
-    MOVQ src, tmp \
-    SHRQ bit, tmp \
-    ANDQ $1, tmp  \
-    NEGQ tmp      \
-    MOVQ tmp, to1 \
-    VSHUFPS $0, to1, to1, to2
-    // VPBROADCASTB to1, to2
-    // Can't use VPBROADCASTB because it is AVX2 instruction
-    //https://software.intel.com/en-us/forums/intel-isa-extensions/topic/301461
+#define mask(bit, tmp, to) \
+   VPSRLW bit, X10, tmp \
+   VPAND X12, tmp, to \ // to = 0x000<bit>000<bit>...
+   VPSUBW to, X13, to   // to = 0xFFFF.. or 0x0000 depending on bit
 
 #define mulBit(bit) \
     VMOVDQU X0, X8 \
@@ -30,7 +23,7 @@
     VXORPD X1, X5, X0 \
     mul2(X2, X5, X6, X7) \
     VXORPD X3, X5, X2 \
-    mask(bit, CX, DX, X6, X5) \
+    mask(bit, X6, X5) \
     VANDPD X0, X5, X1 \
     VXORPD X8, X1, X1 \
     VANDPD X2, X5, X3 \
@@ -49,6 +42,11 @@ TEXT ·mulBitRight(SB),NOSPLIT,$0
     MOVQ c11+24(FP), DX
     VMOVDQU (DX), X3
 
+    VPXOR X13, X13, X13     // Y13 = 0x0000...
+    VPCMPEQB X14, X14, X14  // Y14 = 0xFFFF...
+    VPSUBQ X14, X13, X13
+    VPSLLQ $63, X13, X14
+
     mul2(X0, X5, X6, X7) // c00 *= 2
     VXORPD X5, X1, X0    // c00 += c01
     mul2(X2, X5, X6, X7) // c10 *= 2
@@ -77,8 +75,19 @@ TEXT ·mulByteRight(SB),NOSPLIT,$0
     VMOVDQU (CX), X2
     MOVQ c11+24(FP), DX
     VMOVDQU (DX), X3
+    MOVQ $0, CX
     MOVB b+32(FP), CX
 
+    VPXOR X13, X13, X13     // X13 = 0x0000...
+    VPCMPEQB X14, X14, X14  // X14 = 0xFFFF...
+    VPSUBQ X14, X13, X10
+    VPSUBW X14, X13, X12    // X12 = 0x00010001... (packed words of 1)
+    VPSLLQ $63, X10, X14    // X14 = 0x10000000... (packed quad-words with HSB set)
+
+    MOVQ CX, X10
+    VPSHUFLW $0, X10, X11
+    VPSHUFD $0, X11, X10
+
     mulBit($7)
     mulBit($6)
     mulBit($5)