Index: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
@@ -522,6 +522,13 @@
   defm LDRAA  : AuthLoad<0, "ldraa", simm10Scaled>;
   defm LDRAB  : AuthLoad<1, "ldrab", simm10Scaled>;
 
+  // v8.3a floating point conversion for javascript
+  let Predicates = [HasV8_3a, HasFPARMv8] in
+  def FJCVTZS  : BaseFPToIntegerUnscaled<0b01, 0b11, 0b110, FPR64, GPR32,
+                                        "fjcvtzs", []> {
+    let Inst{31} = 0;
+  }
+
 } // HasV8_3A
 
 def : InstAlias<"clrex", (CLREX 0xf)>;
Index: llvm/trunk/lib/Target/ARM/ARMInstrVFP.td
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMInstrVFP.td
+++ llvm/trunk/lib/Target/ARM/ARMInstrVFP.td
@@ -1561,6 +1561,15 @@
 }
 }
 
+// v8.3-a Javascript Convert to Signed fixed-point
+def VJCVT : AVConv1IsD_Encode<0b11101, 0b11, 0b1001, 0b1011,
+                                (outs SPR:$Sd), (ins DPR:$Dm),
+                                IIC_fpCVTDI, "vjcvt", ".s32.f64\t$Sd, $Dm",
+                                []>,
+            Requires<[HasFPARMv8, HasV8_3a]> {
+  let Inst{7} = 1; // Z bit
+}
+
 // Convert between floating-point and fixed-point
 // Data type for fixed-point naming convention:
 //   S16 (U=0, sx=0) -> SH
Index: llvm/trunk/test/MC/AArch64/armv8.3a-js.s
===================================================================
--- llvm/trunk/test/MC/AArch64/armv8.3a-js.s
+++ llvm/trunk/test/MC/AArch64/armv8.3a-js.s
@@ -0,0 +1,10 @@
+// RUN: llvm-mc -triple aarch64-none-linux-gnu -show-encoding -mattr=+v8.3a < %s 2>&1 | FileCheck %s
+// RUN: not llvm-mc -triple aarch64-none-linux-gnu < %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-REQ < %t %s
+// RUN: not llvm-mc -triple aarch64-none-linux-gnu -mattr=+v8.3a,-fp-armv8 < %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-NOFP < %t %s
+
+  fjcvtzs w0, d0
+// CHECK: fjcvtzs w0, d0    // encoding: [0x00,0x00,0x7e,0x1e]
+// CHECK-REQ: error: instruction requires: armv8.3a
+// CHECK-NOFP: error: instruction requires: fp-armv8
Index: llvm/trunk/test/MC/ARM/armv8.3a-js.s
===================================================================
--- llvm/trunk/test/MC/ARM/armv8.3a-js.s
+++ llvm/trunk/test/MC/ARM/armv8.3a-js.s
@@ -0,0 +1,16 @@
+// RUN:     llvm-mc -triple   arm-none-none-eabi -show-encoding -mattr=+v8.3a,+fp-armv8 < %s 2>&1 | FileCheck %s --check-prefix=ARM
+// RUN:     llvm-mc -triple thumb-none-none-eabi -show-encoding -mattr=+v8.3a,+fp-armv8 < %s 2>&1 | FileCheck %s --check-prefix=THUMB
+// RUN: not llvm-mc -triple   arm-none-none-eabi -show-encoding -mattr=+v8.2a,+fp-armv8 < %s 2>&1 | FileCheck --check-prefix=REQ-V83 %s
+// RUN: not llvm-mc -triple   arm-none-none-eabi -show-encoding -mattr=+v8.3a,-fp-armv8 < %s 2>&1 | FileCheck --check-prefix=REQ-FP %s
+
+  vjcvt.s32.f64 s1, d2
+// ARM: vjcvt.s32.f64 s1, d2    @ encoding: [0xc2,0x0b,0xf9,0xee]
+// THUMB: vjcvt.s32.f64 s1, d2    @ encoding: [0xf9,0xee,0xc2,0x0b]
+// REQ-V83: error: instruction requires: armv8.3a
+// REQ-FP: error: instruction requires: FPARMv8
+
+  vjcvt.s32.f64 s17, d18
+// ARM: vjcvt.s32.f64 s17, d18    @ encoding: [0xe2,0x8b,0xf9,0xee]
+// THUMB: vjcvt.s32.f64 s17, d18    @ encoding: [0xf9,0xee,0xe2,0x8b]
+// REQ-V83: error: instruction requires: armv8.3a
+// REQ-FP: error: instruction requires: FPARMv8
Index: llvm/trunk/test/MC/Disassembler/AArch64/armv8.3a-js.txt
===================================================================
--- llvm/trunk/test/MC/Disassembler/AArch64/armv8.3a-js.txt
+++ llvm/trunk/test/MC/Disassembler/AArch64/armv8.3a-js.txt
@@ -0,0 +1,3 @@
+# RUN: llvm-mc -triple aarch64-none-linux-gnu -mattr=+v8.3a --disassemble < %s | FileCheck %s
+# CHECK: fjcvtzs w0, d0
+[0x00,0x00,0x7e,0x1e]
Index: llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-arm.txt
===================================================================
--- llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-arm.txt
+++ llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-arm.txt
@@ -0,0 +1,10 @@
+# RUN:     llvm-mc -triple arm-none-eabi -mattr=+v8.3a,+fp-armv8 --disassemble < %s 2>&1 | FileCheck %s
+# RUN: not llvm-mc -triple arm-none-eabi -mattr=+v8.2a,+fp-armv8 --disassemble < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
+# RUN: not llvm-mc -triple arm-none-eabi -mattr=+v8.3a,-fp-armv8 --disassemble < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
+
+[0xc2,0x0b,0xf9,0xee]
+# CHECK: vjcvt.s32.f64 s1, d2
+# UNDEF: :[[@LINE-2]]:{{[0-9]+}}: warning: invalid instruction encoding
+[0xe2,0x8b,0xf9,0xee]
+# CHECK: vjcvt.s32.f64 s17, d18
+# UNDEF: :[[@LINE-2]]:{{[0-9]+}}: warning: invalid instruction encoding
Index: llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-thumb.txt
===================================================================
--- llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-thumb.txt
+++ llvm/trunk/test/MC/Disassembler/ARM/armv8.3a-js-thumb.txt
@@ -0,0 +1,10 @@
+# RUN:     llvm-mc -triple thumb-none-eabi -mattr=+v8.3a,+fp-armv8 --disassemble < %s 2>&1 | FileCheck %s
+# RUN: not llvm-mc -triple thumb-none-eabi -mattr=+v8.2a,+fp-armv8 --disassemble < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
+# RUN: not llvm-mc -triple thumb-none-eabi -mattr=+v8.3a,-fp-armv8 --disassemble < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
+
+[0xf9,0xee,0xc2,0x0b]
+# CHECK: vjcvt.s32.f64 s1, d2
+# UNDEF: :[[@LINE-2]]:{{[0-9]+}}: warning: invalid instruction encoding
+[0xf9,0xee,0xe2,0x8b]
+# CHECK: vjcvt.s32.f64 s17, d18
+# UNDEF: :[[@LINE-2]]:{{[0-9]+}}: warning: invalid instruction encoding