Index: lib/Basic/Targets/WebAssembly.h
===================================================================
--- lib/Basic/Targets/WebAssembly.h
+++ lib/Basic/Targets/WebAssembly.h
@@ -41,9 +41,11 @@
     SigAtomicType = SignedLong;
     LongDoubleWidth = LongDoubleAlign = 128;
     LongDoubleFormat = &llvm::APFloat::IEEEquad();
-    SizeType = UnsignedInt;
-    PtrDiffType = SignedInt;
-    IntPtrType = SignedInt;
+    // size_t being unsigned long for both wasm32 and wasm64 makes mangled names
+    // more consistent between the two.
+    SizeType = UnsignedLong;
+    PtrDiffType = SignedLong;
+    IntPtrType = SignedLong;
   }
 
 protected:
@@ -111,6 +113,13 @@
   explicit WebAssembly32TargetInfo(const llvm::Triple &T,
                                    const TargetOptions &Opts)
       : WebAssemblyTargetInfo(T, Opts) {
+    if (T.isOSBinFormatELF()) {
+        // Make size_t unsigned int, for compatibility with the asm.js
+        // ecosystem, including Emscripten symbols files.
+        SizeType = UnsignedInt;
+        PtrDiffType = SignedInt;
+        IntPtrType = SignedInt;
+    }
     MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
     resetDataLayout("e-m:e-p:32:32-i64:64-n32:64-S128");
   }
@@ -129,9 +138,6 @@
     LongAlign = LongWidth = 64;
     PointerAlign = PointerWidth = 64;
     MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
-    SizeType = UnsignedLong;
-    PtrDiffType = SignedLong;
-    IntPtrType = SignedLong;
     resetDataLayout("e-m:e-p:64:64-i64:64-n32:64-S128");
   }
 
Index: test/Preprocessor/init.c
===================================================================
--- test/Preprocessor/init.c
+++ test/Preprocessor/init.c
@@ -9053,7 +9053,32 @@
 // XCORE:#define __LITTLE_ENDIAN__ 1
 // XCORE:#define __XS1B__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm32-unknown-unknown \
+// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm32-unknown-unknown-elf \
+// RUN:   < /dev/null \
+// RUN:   | FileCheck -match-full-lines -check-prefix=WEBASSEMBLYELF32 %s
+//
+// WEBASSEMBLYELF32:#define __INTPTR_FMTd__ "d"
+// WEBASSEMBLYELF32:#define __INTPTR_FMTi__ "i"
+// WEBASSEMBLYELF32:#define __INTPTR_MAX__ 2147483647
+// WEBASSEMBLYELF32:#define __INTPTR_TYPE__ int
+// WEBASSEMBLYELF32:#define __PTRDIFF_FMTd__ "d"
+// WEBASSEMBLYELF32:#define __PTRDIFF_FMTi__ "i"
+// WEBASSEMBLYELF32:#define __PTRDIFF_MAX__ 2147483647
+// WEBASSEMBLYELF32:#define __PTRDIFF_TYPE__ int
+// WEBASSEMBLYELF32:#define __SIZE_FMTX__ "X"
+// WEBASSEMBLYELF32:#define __SIZE_FMTo__ "o"
+// WEBASSEMBLYELF32:#define __SIZE_FMTu__ "u"
+// WEBASSEMBLYELF32:#define __SIZE_FMTx__ "x"
+// WEBASSEMBLYELF32:#define __SIZE_MAX__ 4294967295U
+// WEBASSEMBLYELF32:#define __SIZE_TYPE__ unsigned int
+// WEBASSEMBLYELF32:#define __UINTPTR_FMTX__ "X"
+// WEBASSEMBLYELF32:#define __UINTPTR_FMTo__ "o"
+// WEBASSEMBLYELF32:#define __UINTPTR_FMTu__ "u"
+// WEBASSEMBLYELF32:#define __UINTPTR_FMTx__ "x"
+// WEBASSEMBLYELF32:#define __UINTPTR_MAX__ 4294967295U
+// WEBASSEMBLYELF32:#define __UINTPTR_TYPE__ unsigned int
+//
+// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm32-unknown-unknown-wasm \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix=WEBASSEMBLY32 %s
 //
@@ -9158,10 +9183,10 @@
 // WEBASSEMBLY32-NEXT:#define __INTMAX_MAX__ 9223372036854775807LL
 // WEBASSEMBLY32-NEXT:#define __INTMAX_TYPE__ long long int
 // WEBASSEMBLY32-NEXT:#define __INTMAX_WIDTH__ 64
-// WEBASSEMBLY32-NEXT:#define __INTPTR_FMTd__ "d"
-// WEBASSEMBLY32-NEXT:#define __INTPTR_FMTi__ "i"
-// WEBASSEMBLY32-NEXT:#define __INTPTR_MAX__ 2147483647
-// WEBASSEMBLY32-NEXT:#define __INTPTR_TYPE__ int
+// WEBASSEMBLY32-NEXT:#define __INTPTR_FMTd__ "ld"
+// WEBASSEMBLY32-NEXT:#define __INTPTR_FMTi__ "li"
+// WEBASSEMBLY32-NEXT:#define __INTPTR_MAX__ 2147483647L
+// WEBASSEMBLY32-NEXT:#define __INTPTR_TYPE__ long int
 // WEBASSEMBLY32-NEXT:#define __INTPTR_WIDTH__ 32
 // WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTd__ "hd"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTi__ "hi"
@@ -9226,10 +9251,10 @@
 // WEBASSEMBLY32-NEXT:#define __ORDER_PDP_ENDIAN__ 3412
 // WEBASSEMBLY32-NEXT:#define __POINTER_WIDTH__ 32
 // WEBASSEMBLY32-NEXT:#define __PRAGMA_REDEFINE_EXTNAME 1
-// WEBASSEMBLY32-NEXT:#define __PTRDIFF_FMTd__ "d"
-// WEBASSEMBLY32-NEXT:#define __PTRDIFF_FMTi__ "i"
-// WEBASSEMBLY32-NEXT:#define __PTRDIFF_MAX__ 2147483647
-// WEBASSEMBLY32-NEXT:#define __PTRDIFF_TYPE__ int
+// WEBASSEMBLY32-NEXT:#define __PTRDIFF_FMTd__ "ld"
+// WEBASSEMBLY32-NEXT:#define __PTRDIFF_FMTi__ "li"
+// WEBASSEMBLY32-NEXT:#define __PTRDIFF_MAX__ 2147483647L
+// WEBASSEMBLY32-NEXT:#define __PTRDIFF_TYPE__ long int
 // WEBASSEMBLY32-NEXT:#define __PTRDIFF_WIDTH__ 32
 // WEBASSEMBLY32-NOT:#define __REGISTER_PREFIX__
 // WEBASSEMBLY32-NEXT:#define __SCHAR_MAX__ 127
@@ -9249,12 +9274,12 @@
 // WEBASSEMBLY32-NEXT:#define __SIZEOF_SIZE_T__ 4
 // WEBASSEMBLY32-NEXT:#define __SIZEOF_WCHAR_T__ 4
 // WEBASSEMBLY32-NEXT:#define __SIZEOF_WINT_T__ 4
-// WEBASSEMBLY32-NEXT:#define __SIZE_FMTX__ "X"
-// WEBASSEMBLY32-NEXT:#define __SIZE_FMTo__ "o"
-// WEBASSEMBLY32-NEXT:#define __SIZE_FMTu__ "u"
-// WEBASSEMBLY32-NEXT:#define __SIZE_FMTx__ "x"
-// WEBASSEMBLY32-NEXT:#define __SIZE_MAX__ 4294967295U
-// WEBASSEMBLY32-NEXT:#define __SIZE_TYPE__ unsigned int
+// WEBASSEMBLY32-NEXT:#define __SIZE_FMTX__ "lX"
+// WEBASSEMBLY32-NEXT:#define __SIZE_FMTo__ "lo"
+// WEBASSEMBLY32-NEXT:#define __SIZE_FMTu__ "lu"
+// WEBASSEMBLY32-NEXT:#define __SIZE_FMTx__ "lx"
+// WEBASSEMBLY32-NEXT:#define __SIZE_MAX__ 4294967295UL
+// WEBASSEMBLY32-NEXT:#define __SIZE_TYPE__ long unsigned int
 // WEBASSEMBLY32-NEXT:#define __SIZE_WIDTH__ 32
 // WEBASSEMBLY32-NEXT:#define __STDC_HOSTED__ 0
 // WEBASSEMBLY32-NOT:#define __STDC_MB_MIGHT_NEQ_WC__
@@ -9302,12 +9327,12 @@
 // WEBASSEMBLY32-NEXT:#define __UINTMAX_MAX__ 18446744073709551615ULL
 // WEBASSEMBLY32-NEXT:#define __UINTMAX_TYPE__ long long unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINTMAX_WIDTH__ 64
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTX__ "X"
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTo__ "o"
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTu__ "u"
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTx__ "x"
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_MAX__ 4294967295U
-// WEBASSEMBLY32-NEXT:#define __UINTPTR_TYPE__ unsigned int
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTX__ "lX"
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTo__ "lo"
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTu__ "lu"
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTx__ "lx"
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_MAX__ 4294967295UL
+// WEBASSEMBLY32-NEXT:#define __UINTPTR_TYPE__ long unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_WIDTH__ 32
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTX__ "hX"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTo__ "ho"
@@ -9384,7 +9409,7 @@
 // WEBASSEMBLY32-NOT:#define __wasm64__
 // WEBASSEMBLY32-NEXT:#define __wasm__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm64-unknown-unknown \
+// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm64-unknown-unknown-wasm \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix=WEBASSEMBLY64 %s
 //