diff --git a/emscripten-version.txt b/emscripten-version.txt
index 5f96aa7b346..f2c16746929 100644
--- a/emscripten-version.txt
+++ b/emscripten-version.txt
@@ -1,2 +1,2 @@
-1.23.0
+1.23.1
 
diff --git a/lib/Target/JSBackend/CallHandlers.h b/lib/Target/JSBackend/CallHandlers.h
index 9b5c5e33946..bcfadc8e231 100644
--- a/lib/Target/JSBackend/CallHandlers.h
+++ b/lib/Target/JSBackend/CallHandlers.h
@@ -450,7 +450,7 @@ DEF_CALL_HANDLER(llvm_cttz_i32, {
 
 // vector ops
 DEF_CALL_HANDLER(emscripten_float32x4_signmask, {
-  return getAssign(CI) + "SIMD.float32x4.bitsToInt32x4(" + getValueAsStr(CI->getOperand(0)) + ").signMask";
+  return getAssign(CI) + getValueAsStr(CI->getOperand(0)) + ".signMask";
 })
 DEF_CALL_HANDLER(emscripten_float32x4_min, {
   return CH___default__(CI, "SIMD.float32x4.min");
@@ -477,32 +477,32 @@ DEF_CALL_HANDLER(emscripten_float32x4_greaterThan, {
   return CH___default__(CI, "SIMD.float32x4.greaterThan");
 })
 DEF_CALL_HANDLER(emscripten_float32x4_and, {
-  return getAssign(CI) + "SIMD.int32x4.bitsToFloat32x4(SIMD.int32x4.and(SIMD.float32x4.bitsToInt32x4(" +
-                                                      getValueAsStr(CI->getOperand(0)) + "),SIMD.float32x4.bitsToInt32x4(" + getValueAsStr(CI->getOperand(1)) + ")))";
+  return getAssign(CI) + "SIMD.float32x4.fromInt32x4Bits(SIMD.float32x4.and(" +
+      getValueAsStr(CI->getOperand(0)) + ", " + getValueAsStr(CI->getOperand(1)) + "))";
 })
 DEF_CALL_HANDLER(emscripten_float32x4_andNot, {
-  return getAssign(CI) + "SIMD.int32x4.bitsToFloat32x4(SIMD.int32x4.and(SIMD.int32x4.not(SIMD.float32x4.bitsToInt32x4(" +
-                                                      getValueAsStr(CI->getOperand(0)) + ")),SIMD.float32x4.bitsToInt32x4(" + getValueAsStr(CI->getOperand(1)) + ")))";
+  return getAssign(CI) + "SIMD.float32x4.fromInt32x4Bits(SIMD.float32x4.and(SIMD.float32x4.not(" +
+      getValueAsStr(CI->getOperand(0)) + "), " + getValueAsStr(CI->getOperand(1)) + "))";
 })
 DEF_CALL_HANDLER(emscripten_float32x4_or, {
-  return getAssign(CI) + "SIMD.int32x4.bitsToFloat32x4(SIMD.int32x4.or(SIMD.float32x4.bitsToInt32x4(" +
-                                                      getValueAsStr(CI->getOperand(0)) + "),SIMD.float32x4.bitsToInt32x4(" + getValueAsStr(CI->getOperand(1)) + ")))";
+  return getAssign(CI) + "SIMD.float32x4.fromInt32x4Bits(SIMD.float32x4.or(" +
+      getValueAsStr(CI->getOperand(0)) + ", " + getValueAsStr(CI->getOperand(1)) + "))";
 })
 DEF_CALL_HANDLER(emscripten_float32x4_xor, {
-  return getAssign(CI) + "SIMD.int32x4.bitsToFloat32x4(SIMD.int32x4.xor(SIMD.float32x4.bitsToInt32x4(" +
-                                                      getValueAsStr(CI->getOperand(0)) + "),SIMD.float32x4.bitsToInt32x4(" + getValueAsStr(CI->getOperand(1)) + ")))";
+  return getAssign(CI) + "SIMD.float32x4.fromInt32x4Bits(SIMD.float32x4.xor(" +
+      getValueAsStr(CI->getOperand(0)) + ", " + getValueAsStr(CI->getOperand(1)) + "))";
 })
-DEF_CALL_HANDLER(emscripten_int32x4_bitsToFloat32x4, {
-  return CH___default__(CI, "SIMD.int32x4.bitsToFloat32x4");
+DEF_CALL_HANDLER(emscripten_float32x4_fromInt32x4Bits, {
+  return CH___default__(CI, "SIMD.float32x4.fromInt32x4Bits");
 })
-DEF_CALL_HANDLER(emscripten_int32x4_toFloat32x4, {
-  return CH___default__(CI, "SIMD.int32x4.toFloat32x4");
+DEF_CALL_HANDLER(emscripten_float32x4_fromInt32x4, {
+  return CH___default__(CI, "SIMD.float32x4.fromInt32x4");
 })
-DEF_CALL_HANDLER(emscripten_float32x4_bitsToInt32x4, {
-  return CH___default__(CI, "SIMD.float32x4.bitsToInt32x4");
+DEF_CALL_HANDLER(emscripten_int32x4_fromFloat32x4Bits, {
+  return CH___default__(CI, "SIMD.int32x4.fromFloat32x4Bits");
 })
-DEF_CALL_HANDLER(emscripten_float32x4_toInt32x4, {
-  return CH___default__(CI, "SIMD.float32x4.toInt32x4");
+DEF_CALL_HANDLER(emscripten_int32x4_fromFloat32x4, {
+  return CH___default__(CI, "SIMD.int32x4.fromFloat32x4");
 })
 
 #define DEF_BUILTIN_HANDLER(name, to) \
@@ -631,10 +631,10 @@ void setupCallHandlers() {
   SETUP_CALL_HANDLER(emscripten_float32x4_andNot);
   SETUP_CALL_HANDLER(emscripten_float32x4_or);
   SETUP_CALL_HANDLER(emscripten_float32x4_xor);
-  SETUP_CALL_HANDLER(emscripten_int32x4_bitsToFloat32x4);
-  SETUP_CALL_HANDLER(emscripten_int32x4_toFloat32x4);
-  SETUP_CALL_HANDLER(emscripten_float32x4_bitsToInt32x4);
-  SETUP_CALL_HANDLER(emscripten_float32x4_toInt32x4);
+  SETUP_CALL_HANDLER(emscripten_float32x4_fromInt32x4Bits);
+  SETUP_CALL_HANDLER(emscripten_float32x4_fromInt32x4);
+  SETUP_CALL_HANDLER(emscripten_int32x4_fromFloat32x4Bits);
+  SETUP_CALL_HANDLER(emscripten_int32x4_fromFloat32x4);
 
   SETUP_CALL_HANDLER(abs);
   SETUP_CALL_HANDLER(labs);
diff --git a/lib/Target/JSBackend/JSBackend.cpp b/lib/Target/JSBackend/JSBackend.cpp
index 9ab38b8272c..97b7d5f193f 100644
--- a/lib/Target/JSBackend/JSBackend.cpp
+++ b/lib/Target/JSBackend/JSBackend.cpp
@@ -1019,9 +1019,18 @@ std::string JSWriter::getConstant(const Constant* CV, AsmCast sign) {
     }
     return CI->getValue().toString(10, sign != ASM_UNSIGNED);
   } else if (isa<UndefValue>(CV)) {
-    std::string S = CV->getType()->isFloatingPointTy() ? "+0" : "0"; // XXX refactor this
-    if (PreciseF32 && CV->getType()->isFloatTy() && !(sign & ASM_FFI_OUT)) {
-      S = "Math_fround(" + S + ")";
+    std::string S;
+    if (VectorType *VT = dyn_cast<VectorType>(CV->getType())) {
+      if (VT->getElementType()->isIntegerTy()) {
+        S = "SIMD.int32x4.splat(0)";
+      } else {
+        S = "SIMD.float32x4.splat(0.0)";
+      }
+    } else {
+      S = CV->getType()->isFloatingPointTy() ? "+0" : "0"; // XXX refactor this
+      if (PreciseF32 && CV->getType()->isFloatTy() && !(sign & ASM_FFI_OUT)) {
+        S = "Math_fround(" + S + ")";
+      }
     }
     return S;
   } else if (isa<ConstantAggregateZero>(CV)) {
@@ -1145,9 +1154,9 @@ bool JSWriter::generateSIMDExpression(const User *I, raw_string_ostream& Code) {
       case Instruction::BitCast: {
         Code << getAssignIfNeeded(I);
         if (cast<VectorType>(I->getType())->getElementType()->isIntegerTy()) {
-          Code << "SIMD.float32x4.bitsToInt32x4(" << getValueAsStr(I->getOperand(0)) << ')';
+          Code << "SIMD.int32x4.fromFloat32x4Bits(" << getValueAsStr(I->getOperand(0)) << ')';
         } else {
-          Code << "SIMD.int32x4.bitsToInt32x4(" << getValueAsStr(I->getOperand(0)) << ')';
+          Code << "SIMD.float32x4.fromInt32x4Bits(" << getValueAsStr(I->getOperand(0)) << ')';
         }
         break;
       }