Index: clang/include/clang/Basic/BuiltinsAArch64.def
===================================================================
--- clang/include/clang/Basic/BuiltinsAArch64.def
+++ clang/include/clang/Basic/BuiltinsAArch64.def
@@ -65,6 +65,8 @@
 BUILTIN(__builtin_arm_dsb, "vUi", "nc")
 BUILTIN(__builtin_arm_isb, "vUi", "nc")
 
+BUILTIN(__builtin_arm_jcvt, "Zid", "nc")
+
 // Prefetch
 BUILTIN(__builtin_arm_prefetch, "vvC*UiUiUiUi", "nc")
 
Index: clang/lib/Basic/Targets/AArch64.h
===================================================================
--- clang/lib/Basic/Targets/AArch64.h
+++ clang/lib/Basic/Targets/AArch64.h
@@ -59,6 +59,12 @@
                                MacroBuilder &Builder) const;
   void getTargetDefinesARMV82A(const LangOptions &Opts,
                                MacroBuilder &Builder) const;
+  void getTargetDefinesARMV83A(const LangOptions &Opts,
+                               MacroBuilder &Builder) const;
+  void getTargetDefinesARMV84A(const LangOptions &Opts,
+                               MacroBuilder &Builder) const;
+  void getTargetDefinesARMV85A(const LangOptions &Opts,
+                               MacroBuilder &Builder) const;
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override;
 
Index: clang/lib/Basic/Targets/AArch64.cpp
===================================================================
--- clang/lib/Basic/Targets/AArch64.cpp
+++ clang/lib/Basic/Targets/AArch64.cpp
@@ -118,6 +118,28 @@
   getTargetDefinesARMV81A(Opts, Builder);
 }
 
+void AArch64TargetInfo::getTargetDefinesARMV83A(const LangOptions &Opts,
+                                                MacroBuilder &Builder) const {
+  Builder.defineMacro("__ARM_FEATURE_JCVT", "1");
+  // Also include the Armv8.2 defines
+  getTargetDefinesARMV82A(Opts, Builder);
+}
+
+void AArch64TargetInfo::getTargetDefinesARMV84A(const LangOptions &Opts,
+                                                MacroBuilder &Builder) const {
+  // Also include the Armv8.3 defines
+  // FIXME: Armv8.4 makes some extensions mandatory. Handle them here.
+  getTargetDefinesARMV83A(Opts, Builder);
+}
+
+void AArch64TargetInfo::getTargetDefinesARMV85A(const LangOptions &Opts,
+                                                MacroBuilder &Builder) const {
+  // Also include the Armv8.4 defines
+  // FIXME: Armv8.5 makes some extensions mandatory. Handle them here.
+  getTargetDefinesARMV84A(Opts, Builder);
+}
+
+
 void AArch64TargetInfo::getTargetDefines(const LangOptions &Opts,
                                          MacroBuilder &Builder) const {
   // Target identification.
@@ -209,6 +231,15 @@
   case llvm::AArch64::ArchKind::ARMV8_2A:
     getTargetDefinesARMV82A(Opts, Builder);
     break;
+  case llvm::AArch64::ArchKind::ARMV8_3A:
+    getTargetDefinesARMV83A(Opts, Builder);
+    break;
+  case llvm::AArch64::ArchKind::ARMV8_4A:
+    getTargetDefinesARMV84A(Opts, Builder);
+    break;
+  case llvm::AArch64::ArchKind::ARMV8_5A:
+    getTargetDefinesARMV85A(Opts, Builder);
+    break;
   }
 
   // All of the __sync_(bool|val)_compare_and_swap_(1|2|4|8) builtins work.
@@ -256,6 +287,12 @@
       ArchKind = llvm::AArch64::ArchKind::ARMV8_1A;
     if (Feature == "+v8.2a")
       ArchKind = llvm::AArch64::ArchKind::ARMV8_2A;
+    if (Feature == "+v8.3a")
+      ArchKind = llvm::AArch64::ArchKind::ARMV8_3A;
+    if (Feature == "+v8.4a")
+      ArchKind = llvm::AArch64::ArchKind::ARMV8_4A;
+    if (Feature == "+v8.5a")
+      ArchKind = llvm::AArch64::ArchKind::ARMV8_5A;
     if (Feature == "+fullfp16")
       HasFullFP16 = 1;
     if (Feature == "+dotprod")
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -6956,6 +6956,14 @@
         CGM.getIntrinsic(Intrinsic::bitreverse, Arg->getType()), Arg, "rbit");
   }
 
+  if (BuiltinID == AArch64::BI__builtin_arm_jcvt) {
+    assert((getContext().getTypeSize(E->getType()) == 32) &&
+           "__jcvt of unusual size!");
+    llvm::Value *Arg = EmitScalarExpr(E->getArg(0));
+    return Builder.CreateCall(
+        CGM.getIntrinsic(Intrinsic::aarch64_fjcvtzs), Arg);
+  }
+
   if (BuiltinID == AArch64::BI__clear_cache) {
     assert(E->getNumArgs() == 2 && "__clear_cache takes 2 arguments");
     const FunctionDecl *FD = E->getDirectCallee();
Index: clang/lib/Headers/arm_acle.h
===================================================================
--- clang/lib/Headers/arm_acle.h
+++ clang/lib/Headers/arm_acle.h
@@ -597,6 +597,14 @@
 }
 #endif
 
+/* Armv8.3-A Javascript conversion intrinsic */
+#if __ARM_64BIT_STATE && defined(__ARM_FEATURE_JCVT)
+static __inline__ int32_t __attribute__((__always_inline__, __nodebug__))
+__jcvt(double __a) {
+  return __builtin_arm_jcvt(__a);
+}
+#endif
+
 /* 10.1 Special register intrinsics */
 #define __arm_rsr(sysreg) __builtin_arm_rsr(sysreg)
 #define __arm_rsr64(sysreg) __builtin_arm_rsr64(sysreg)
Index: clang/test/CodeGen/arm_acle.c
===================================================================
--- clang/test/CodeGen/arm_acle.c
+++ clang/test/CodeGen/arm_acle.c
@@ -2,6 +2,9 @@
 // RUN: %clang_cc1 -ffreestanding -triple armv8-eabi -target-cpu cortex-a57 -O2  -fexperimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=ARM -check-prefix=AArch32 -check-prefix=ARM-NEWPM -check-prefix=AArch32-NEWPM
 // RUN: %clang_cc1 -ffreestanding -triple aarch64-eabi -target-cpu cortex-a57 -target-feature +neon -target-feature +crc -target-feature +crypto -O2 -fno-experimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=ARM -check-prefix=AArch64 -check-prefix=ARM-LEGACY -check-prefix=AArch64-LEGACY
 // RUN: %clang_cc1 -ffreestanding -triple aarch64-eabi -target-cpu cortex-a57 -target-feature +neon -target-feature +crc -target-feature +crypto -O2 -fexperimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=ARM -check-prefix=AArch64 -check-prefix=ARM-NEWPM -check-prefix=AArch64-NEWPM
+// RUN: %clang_cc1 -ffreestanding -triple aarch64-eabi -target-cpu cortex-a57 -target-feature +v8.3a -O2 -fexperimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=AArch64-v8_3
+// RUN: %clang_cc1 -ffreestanding -triple aarch64-eabi -target-cpu cortex-a57 -target-feature +v8.4a -O2 -fexperimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=AArch64-v8_3
+// RUN: %clang_cc1 -ffreestanding -triple aarch64-eabi -target-cpu cortex-a57 -target-feature +v8.5a -O2 -fexperimental-new-pass-manager -S -emit-llvm -o - %s | FileCheck %s -check-prefix=AArch64-v8_3
 
 #include <arm_acle.h>
 
@@ -823,3 +826,11 @@
 
 // AArch64: ![[M0]] = !{!"1:2:3:4:5"}
 // AArch64: ![[M1]] = !{!"sysreg"}
+
+// AArch64-v8_3-LABEL: @test_jcvt(
+// AArch64-v8_3: call i32 @llvm.aarch64.fjcvtzs
+#ifdef __ARM_64BIT_STATE
+int32_t test_jcvt(double v) {
+  return __jcvt(v);
+}
+#endif
Index: clang/test/CodeGen/builtins-arm64.c
===================================================================
--- clang/test/CodeGen/builtins-arm64.c
+++ clang/test/CodeGen/builtins-arm64.c
@@ -58,6 +58,12 @@
 // CHECK: call {{.*}} @llvm.prefetch(i8* null, i32 0, i32 3, i32 0)
 }
 
+int32_t jcvt(double v) {
+  //CHECK-LABEL: @jcvt(
+  //CHECK: call i32 @llvm.aarch64.fjcvtzs
+  return __builtin_arm_jcvt(v);
+}
+
 __typeof__(__builtin_arm_rsr("1:2:3:4:5")) rsr(void);
 
 uint32_t rsr() {
Index: llvm/include/llvm/IR/IntrinsicsAArch64.td
===================================================================
--- llvm/include/llvm/IR/IntrinsicsAArch64.td
+++ llvm/include/llvm/IR/IntrinsicsAArch64.td
@@ -31,6 +31,8 @@
 def int_aarch64_udiv : Intrinsic<[llvm_anyint_ty], [LLVMMatchType<0>,
                                 LLVMMatchType<0>], [IntrNoMem]>;
 
+def int_aarch64_fjcvtzs : Intrinsic<[llvm_i32_ty], [llvm_double_ty], [IntrNoMem]>;
+
 //===----------------------------------------------------------------------===//
 // HINT
 
Index: llvm/lib/Target/AArch64/AArch64InstrInfo.td
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -717,7 +717,9 @@
 // v8.3a floating point conversion for javascript
 let Predicates = [HasJS, HasFPARMv8] in
 def FJCVTZS  : BaseFPToIntegerUnscaled<0b01, 0b11, 0b110, FPR64, GPR32,
-                                      "fjcvtzs", []> {
+                                      "fjcvtzs",
+                                      [(set GPR32:$Rd,
+                                         (int_aarch64_fjcvtzs FPR64:$Rn))]> {
   let Inst{31} = 0;
 } // HasJS, HasFPARMv8
 
Index: llvm/test/CodeGen/AArch64/fjcvtzs.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/fjcvtzs.ll
@@ -0,0 +1,10 @@
+; RUN: llc -mtriple=arm64-eabi -mattr=+jsconv -o - %s | FileCheck %s
+
+define i32 @test_jcvt(double %v) {
+; CHECK-LABEL: test_jcvt:
+; CHECK: fjcvtzs w0, d0
+  %val = call i32 @llvm.aarch64.fjcvtzs(double %v)
+  ret i32 %val
+}
+
+declare i32 @llvm.aarch64.fjcvtzs(double)