diff --git a/compiler/dex/quick/x86/assemble_x86.cc b/compiler/dex/quick/x86/assemble_x86.cc
index 3f54798..f06f08e 100644
--- a/compiler/dex/quick/x86/assemble_x86.cc
+++ b/compiler/dex/quick/x86/assemble_x86.cc
@@ -325,11 +325,21 @@
 { kX86 ## opname ## RM, kRegMem,   IS_LOAD | IS_TERTIARY_OP | reg_def | REG_USE1,  { prefix, 0, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RM", "!0r,[!1r+!2d]" }, \
 { kX86 ## opname ## RA, kRegArray, IS_LOAD | IS_QUIN_OP     | reg_def | REG_USE12, { prefix, 0, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RA", "!0r,[!1r+!2r<<!3d+!4d]" }
 
+#define EXT_0F_REX_NO_PREFIX_ENCODING_MAP(opname, opcode, reg_def) \
+{ kX86 ## opname ## RR, kRegReg,             IS_BINARY_OP   | reg_def | REG_USE1,  { REX, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RR", "!0r,!1r" }, \
+{ kX86 ## opname ## RM, kRegMem,   IS_LOAD | IS_TERTIARY_OP | reg_def | REG_USE1,  { REX, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RM", "!0r,[!1r+!2d]" }, \
+{ kX86 ## opname ## RA, kRegArray, IS_LOAD | IS_QUIN_OP     | reg_def | REG_USE12, { REX, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RA", "!0r,[!1r+!2r<<!3d+!4d]" }
+
 #define EXT_0F_REX_W_ENCODING_MAP(opname, prefix, opcode, reg_def) \
 { kX86 ## opname ## RR, kRegReg,             IS_BINARY_OP   | reg_def | REG_USE1,  { prefix, REX_W, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RR", "!0r,!1r" }, \
 { kX86 ## opname ## RM, kRegMem,   IS_LOAD | IS_TERTIARY_OP | reg_def | REG_USE1,  { prefix, REX_W, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RM", "!0r,[!1r+!2d]" }, \
 { kX86 ## opname ## RA, kRegArray, IS_LOAD | IS_QUIN_OP     | reg_def | REG_USE12, { prefix, REX_W, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RA", "!0r,[!1r+!2r<<!3d+!4d]" }
 
+#define EXT_0F_REX_W_NO_PREFIX_ENCODING_MAP(opname, opcode, reg_def) \
+{ kX86 ## opname ## RR, kRegReg,             IS_BINARY_OP   | reg_def | REG_USE1,  { REX_W, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RR", "!0r,!1r" }, \
+{ kX86 ## opname ## RM, kRegMem,   IS_LOAD | IS_TERTIARY_OP | reg_def | REG_USE1,  { REX_W, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RM", "!0r,[!1r+!2d]" }, \
+{ kX86 ## opname ## RA, kRegArray, IS_LOAD | IS_QUIN_OP     | reg_def | REG_USE12, { REX_W, 0x00, 0x0F, opcode, 0, 0, 0, 0, false }, #opname "RA", "!0r,[!1r+!2r<<!3d+!4d]" }
+
 #define EXT_0F_ENCODING2_MAP(opname, prefix, opcode, opcode2, reg_def) \
 { kX86 ## opname ## RR, kRegReg,             IS_BINARY_OP   | reg_def | REG_USE1,  { prefix, 0, 0x0F, opcode, opcode2, 0, 0, 0, false }, #opname "RR", "!0r,!1r" }, \
 { kX86 ## opname ## RM, kRegMem,   IS_LOAD | IS_TERTIARY_OP | reg_def | REG_USE1,  { prefix, 0, 0x0F, opcode, opcode2, 0, 0, 0, false }, #opname "RM", "!0r,[!1r+!2d]" }, \
@@ -481,6 +491,10 @@
   EXT_0F_ENCODING_MAP(Movzx16, 0x00, 0xB7, REG_DEF0),
   EXT_0F_ENCODING_MAP(Movsx8,  0x00, 0xBE, REG_DEF0),
   EXT_0F_ENCODING_MAP(Movsx16, 0x00, 0xBF, REG_DEF0),
+  EXT_0F_REX_NO_PREFIX_ENCODING_MAP(Movzx8q, 0xB6, REG_DEF0),
+  EXT_0F_REX_W_NO_PREFIX_ENCODING_MAP(Movzx16q, 0xB7, REG_DEF0),
+  EXT_0F_REX_NO_PREFIX_ENCODING_MAP(Movsx8q, 0xBE, REG_DEF0),
+  EXT_0F_REX_W_NO_PREFIX_ENCODING_MAP(Movsx16q, 0xBF, REG_DEF0),
 #undef EXT_0F_ENCODING_MAP
 
   { kX86Jcc8,  kJcc,  IS_BINARY_OP | IS_BRANCH | NEEDS_FIXUP | USES_CCODES, { 0,             0, 0x70, 0,    0, 0, 0, 0, false }, "Jcc8",  "!1c !0t" },
@@ -827,7 +841,8 @@
       CHECK(strchr(entry->name, '8') != nullptr) << entry->name;
     } else {
       if (entry->skeleton.immediate_bytes != 1) {  // Ignore ...I8 instructions.
-        if (!StartsWith(entry->name, "Movzx8") && !StartsWith(entry->name, "Movsx8")) {
+        if (!StartsWith(entry->name, "Movzx8") && !StartsWith(entry->name, "Movsx8")
+           && !StartsWith(entry->name, "Movzx8q") && !StartsWith(entry->name, "Movsx8q")) {
           CHECK(strchr(entry->name, '8') == nullptr) << entry->name;
         }
       }
diff --git a/compiler/dex/quick/x86/int_x86.cc b/compiler/dex/quick/x86/int_x86.cc
index 48fcd2c..2f914c1 100644
--- a/compiler/dex/quick/x86/int_x86.cc
+++ b/compiler/dex/quick/x86/int_x86.cc
@@ -35,17 +35,12 @@
     rl_src1 = LoadValueWide(rl_src1, kCoreReg);
     rl_src2 = LoadValueWide(rl_src2, kCoreReg);
     RegLocation rl_result = EvalLoc(rl_dest, kCoreReg, true);
-    RegStorage rl_result_wide = RegStorage::Solo64(rl_result.reg.GetRegNum());
     RegStorage temp_reg = AllocTemp();
-    OpRegReg(kOpXor, temp_reg, temp_reg);  // temp = 0
-    OpRegRegReg(kOpSub, rl_result_wide, rl_src1.reg, rl_src2.reg);
-    NewLIR2(kX86Set8R, temp_reg.GetReg(), kX86CondG);  // temp = (src1 > src2) ? 1 : temp
-
-    NewLIR2(kX86Rol64RI, rl_result_wide.GetReg(), 1);
-    OpRegImm(kOpAnd, rl_result.reg, 1);
-    OpRegReg(kOpNeg, rl_result.reg, rl_result.reg);
-    // result = (src1 < src2) ? -1 : 0;
-    OpRegReg(kOpAdd, rl_result.reg, temp_reg);
+    OpRegReg(kOpCmp, rl_src1.reg, rl_src2.reg);
+    NewLIR2(kX86Set8R, rl_result.reg.GetReg(), kX86CondG);   // result = (src1 > src2) ? 1 : 0
+    NewLIR2(kX86Set8R, temp_reg.GetReg(), kX86CondL);  // temp = (src1 >= src2) ? 0 : 1
+    NewLIR2(kX86Sub8RR, rl_result.reg.GetReg(), temp_reg.GetReg());
+    NewLIR2(kX86Movsx8qRR, rl_result.reg.GetReg(), rl_result.reg.GetReg());
 
     StoreValue(rl_dest, rl_result);
     FreeTemp(temp_reg);
diff --git a/compiler/dex/quick/x86/utility_x86.cc b/compiler/dex/quick/x86/utility_x86.cc
index 46e877f..ac5162e 100644
--- a/compiler/dex/quick/x86/utility_x86.cc
+++ b/compiler/dex/quick/x86/utility_x86.cc
@@ -611,8 +611,12 @@
         if (val_lo < 0) {
           val_hi += 1;
         }
-        res = LoadConstantNoClobber(RegStorage::Solo32(r_dest.GetReg()), val_hi);
-        NewLIR2(kX86Sal64RI, r_dest.GetReg(), 32);
+        if (val_hi != 0) {
+          res = LoadConstantNoClobber(RegStorage::Solo32(r_dest.GetReg()), val_hi);
+          NewLIR2(kX86Sal64RI, r_dest.GetReg(), 32);
+        } else {
+          res = NewLIR2(kX86Xor64RR, r_dest.GetReg(), r_dest.GetReg());
+        }
         if (val_lo != 0) {
           NewLIR2(kX86Add64RI, r_dest.GetReg(), val_lo);
         }
diff --git a/compiler/dex/quick/x86/x86_lir.h b/compiler/dex/quick/x86/x86_lir.h
index 28b9dca1..17c44bc 100644
--- a/compiler/dex/quick/x86/x86_lir.h
+++ b/compiler/dex/quick/x86/x86_lir.h
@@ -609,6 +609,10 @@
   Binary0fOpCode(kX86Movzx16),  // zero-extend 16-bit value
   Binary0fOpCode(kX86Movsx8),   // sign-extend 8-bit value
   Binary0fOpCode(kX86Movsx16),  // sign-extend 16-bit value
+  Binary0fOpCode(kX86Movzx8q),   // zero-extend 8-bit value to quad word
+  Binary0fOpCode(kX86Movzx16q),  // zero-extend 16-bit value to quad word
+  Binary0fOpCode(kX86Movsx8q),   // sign-extend 8-bit value to quad word
+  Binary0fOpCode(kX86Movsx16q),  // sign-extend 16-bit value to quad word
 #undef Binary0fOpCode
   kX86Jcc8, kX86Jcc32,  // jCC rel8/32; lir operands - 0: rel, 1: CC, target assigned
   kX86Jmp8, kX86Jmp32,  // jmp rel8/32; lir operands - 0: rel, target assigned
@@ -707,6 +711,8 @@
 #define REX_X 0x42
 // Extension of the ModR/M r/m field, SIB base field, or Opcode reg field
 #define REX_B 0x41
+// Extended register set
+#define REX 0x40
 // Mask extracting the least 3 bits of r0..r15
 #define kRegNumMask32 0x07
 // Value indicating that base or reg is not used