Index: lib/Target/WebAssembly/WebAssemblyInstrCall.td
===================================================================
--- lib/Target/WebAssembly/WebAssemblyInstrCall.td
+++ lib/Target/WebAssembly/WebAssemblyInstrCall.td
@@ -93,26 +93,28 @@
   defm "" : SIMD_CALL<v4f32, "v128.">;
   defm "" : SIMD_CALL<v2f64, "v128.">;
 
-  defm CALL_VOID : I<(outs), (ins function32_op:$callee, variable_ops),
-                     (outs), (ins function32_op:$callee),
-                     [(WebAssemblycall0 (i32 imm:$callee))],
-                     "call    \t$callee", "call\t$callee", 0x10>;
+  let IsCanonical = 1 in {
+    defm CALL_VOID : I<(outs), (ins function32_op:$callee, variable_ops),
+                      (outs), (ins function32_op:$callee),
+                      [(WebAssemblycall0 (i32 imm:$callee))],
+                      "call    \t$callee", "call\t$callee", 0x10>;
 
-  let isCodeGenOnly = 1 in {
-    defm PCALL_INDIRECT_VOID : I<(outs), (ins I32:$callee, variable_ops),
-                                 (outs), (ins I32:$callee),
-                                 [(WebAssemblycall0 I32:$callee)],
-                                 "PSEUDO CALL INDIRECT\t$callee",
-                                 "PSEUDO CALL INDIRECT\t$callee">;
-  } // isCodeGenOnly = 1
+    let isCodeGenOnly = 1 in {
+      defm PCALL_INDIRECT_VOID : I<(outs), (ins I32:$callee, variable_ops),
+                                  (outs), (ins I32:$callee),
+                                  [(WebAssemblycall0 I32:$callee)],
+                                  "PSEUDO CALL INDIRECT\t$callee",
+                                  "PSEUDO CALL INDIRECT\t$callee">;
+    } // isCodeGenOnly = 1
 
-  defm CALL_INDIRECT_VOID : I<(outs),
-                              (ins TypeIndex:$type, i32imm:$flags,
-                                variable_ops),
-                              (outs), (ins TypeIndex:$type, i32imm:$flags),
-                              [],
-                              "call_indirect\t", "call_indirect\t$type",
-                              0x11>;
+    defm CALL_INDIRECT_VOID : I<(outs),
+                                (ins TypeIndex:$type, i32imm:$flags,
+                                  variable_ops),
+                                (outs), (ins TypeIndex:$type, i32imm:$flags),
+                                [],
+                                "call_indirect\t", "call_indirect\t$type",
+                                0x11>;
+  }
 } // Uses = [SP32,SP64], isCall = 1
 
 // Patterns for matching a direct call to a global address.
Index: lib/Target/WebAssembly/WebAssemblyInstrControl.td
===================================================================
--- lib/Target/WebAssembly/WebAssemblyInstrControl.td
+++ lib/Target/WebAssembly/WebAssemblyInstrControl.td
@@ -81,6 +81,10 @@
 defm END_BLOCK : NRI<(outs), (ins), [], "end_block", 0x0b>;
 defm END_LOOP  : NRI<(outs), (ins), [], "end_loop", 0x0b>;
 defm END_IF    : NRI<(outs), (ins), [], "end_if", 0x0b>;
+// Generic instruction, for disassembler.
+let IsCanonical = 1 in {
+  defm END       : NRI<(outs), (ins), [], "end", 0x0b>;
+}
 let isTerminator = 1, isBarrier = 1 in
 defm END_FUNCTION : NRI<(outs), (ins), [], "end_function", 0x0b>;
 } // Uses = [VALUE_STACK], Defs = [VALUE_STACK]
Index: lib/Target/WebAssembly/WebAssemblyInstrFormats.td
===================================================================
--- lib/Target/WebAssembly/WebAssemblyInstrFormats.td
+++ lib/Target/WebAssembly/WebAssemblyInstrFormats.td
@@ -22,6 +22,9 @@
   let Namespace   = "WebAssembly";
   let Pattern     = [];
   let AsmString   = asmstr;
+  // When there are multiple instructions that map to the same encoding (in
+  // e.g. the disassembler use case) prefer the one where IsCanonical == 1.
+  bit IsCanonical = 0;
 }
 
 // Normal instructions. Default instantiation of a WebAssemblyInst.
Index: lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
===================================================================
--- lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -125,12 +125,14 @@
                      ImmI16:$i0, ImmI16:$i1, ImmI16:$i2, ImmI16:$i3,
                      ImmI16:$i4, ImmI16:$i5, ImmI16:$i6, ImmI16:$i7),
                    "$i0, $i1, $i2, $i3, $i4, $i5, $i6, $i7">;
-defm "" : ConstVec<v4i32,
-                   (ins vec_i32imm_op:$i0, vec_i32imm_op:$i1,
-                        vec_i32imm_op:$i2, vec_i32imm_op:$i3),
-                   (build_vector (i32 imm:$i0), (i32 imm:$i1),
-                                 (i32 imm:$i2), (i32 imm:$i3)),
-                   "$i0, $i1, $i2, $i3">;
+let IsCanonical = 1 in {
+  defm "" : ConstVec<v4i32,
+                    (ins vec_i32imm_op:$i0, vec_i32imm_op:$i1,
+                          vec_i32imm_op:$i2, vec_i32imm_op:$i3),
+                    (build_vector (i32 imm:$i0), (i32 imm:$i1),
+                                  (i32 imm:$i2), (i32 imm:$i3)),
+                    "$i0, $i1, $i2, $i3">;
+}
 defm "" : ConstVec<v2i64,
                    (ins vec_i64imm_op:$i0, vec_i64imm_op:$i1),
                    (build_vector (i64 imm:$i0), (i64 imm:$i1)),
Index: test/MC/Disassembler/WebAssembly/wasm.txt
===================================================================
--- test/MC/Disassembler/WebAssembly/wasm.txt
+++ test/MC/Disassembler/WebAssembly/wasm.txt
@@ -22,6 +22,10 @@
 # FIXME: WebAssemblyInstPrinter does not print immediates.
 0x11 0x80 0x01 0x00
 
+# CHECK: call 0
+# CHECK-NOT: except_ref.call 0
+0x10 0x00
+
 # CHECK: local.get 128
 0x20 0x80 0x01
 
@@ -30,7 +34,7 @@
 0xFC 0x07
 
 # v128.const is arbitrarily disassembled as v16i8
-# CHECK: v128.const 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+# CHECK: v128.const 50462976, 117835012, 185207048, 252579084
 0xFD 0x02 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
 
 # CHECK: v8x16.shuffle 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
@@ -48,3 +52,7 @@
 # Check br_table, which has its own operand type.
 # CHECK: br_table {0, 1, 2}
 0x0E 0x02 0x00 0x01 0x02
+
+# This can mean end_block/end_loop/end_if/end_function/end_try..
+# CHECK: end
+0x0B
Index: test/MC/WebAssembly/objdump.s
===================================================================
--- test/MC/WebAssembly/objdump.s
+++ test/MC/WebAssembly/objdump.s
@@ -19,8 +19,8 @@
 # CHECK-LABEL: test0:
 # CHECK-NEXT:        .local  f32, f64, v128, v128
 # CHECK-NEXT:       9:       20 02  local.get	2
-# CHECK-NEXT:       b:       0b     end_block
+# CHECK-NEXT:       b:       0b     end
 # CHECK-LABEL: test1:
 # CHECK-NEXT:        .local  i32, i64, except_ref
 # CHECK-NEXT:      14:       20 03  local.get	3
-# CHECK-NEXT:      16:       0b     end_block
+# CHECK-NEXT:      16:       0b     end
Index: utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
===================================================================
--- utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
+++ utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
@@ -50,12 +50,33 @@
     auto IsStackBased =
         StackString &&
         reinterpret_cast<const StringInit *>(StackString)->getValue() == "true";
-    if (IsStackBased && !CGIP.second) {
-      // this picks the first of many typed variants, which is
-      // currently the except_ref one, though this shouldn't matter for
-      // disassembly purposes.
-      CGIP = std::make_pair(I, &CGI);
+    if (!IsStackBased)
+      continue;
+    if (CGIP.second) {
+      // We already have an instruction for this slot, so decide which one
+      // should be the canonical one. This determines which variant gets
+      // printed in a disassembly. We want e.g. "call" not "i32.call", and
+      // "end" when we don't know if its "end_loop" or "end_block" etc.
+      auto IsCanonicalExisting = CGIP.second->TheDef->getValue("IsCanonical")
+                                     ->getValue()
+                                     ->getAsString() == "1";
+      // We already have one marked explicitly as canonical, so keep it.
+      if (IsCanonicalExisting)
+        continue;
+      auto IsCanonicalNew =
+          Def.getValue("IsCanonical")->getValue()->getAsString() == "1";
+      // If the new one is explicitly marked as canonical, take it.
+      if (!IsCanonicalNew) {
+        // Neither the existing or new instruction is canonical.
+        // Pick the one with with the shortest name as heuristic.
+        // Though ideally IsCanonical is always defined for at least one
+        // variant so this never has to apply.
+        if (CGIP.second->AsmString.size() <= CGI.AsmString.size())
+          continue;
+      }
     }
+    // Set this instruction as the one to use.
+    CGIP = std::make_pair(I, &CGI);
   }
   OS << "#include \"MCTargetDesc/WebAssemblyMCTargetDesc.h\"\n";
   OS << "\n";