Fix printing order of opcode prefix and space

Leading whitespaces are used to indiate control depth,
opcode prefix should be printed after the whitespaces.

Change-Id: I0a22864d1d5a2e643b15a4c10909c0387922f8e3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2224959Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jie Pan <jie.pan@intel.com>
Cr-Commit-Position: refs/heads/master@{#68092}

src/wasm/function-body-decoder.cc

@@ -176,8 +176,10 @@ bool PrintRawWasmCode(AccountingAllocator* allocator, const FunctionBody& body,
 
     unsigned offset = 1;
     WasmOpcode opcode = i.current();
-    if (WasmOpcodes::IsPrefixOpcode(opcode)) {
-      os << PrefixName(opcode) << ", ";
+    WasmOpcode prefix = kExprUnreachable;
+    bool has_prefix = WasmOpcodes::IsPrefixOpcode(opcode);
+    if (has_prefix) {
+      prefix = i.current();
       opcode = i.prefixed_opcode();
       offset = 2;
     }
@@ -193,6 +195,10 @@ bool PrintRawWasmCode(AccountingAllocator* allocator, const FunctionBody& body,
         "                                                                ";
     os.write(padding, num_whitespaces);
 
+    if (has_prefix) {
+      os << PrefixName(prefix) << ", ";
+    }
+
     os << RawOpcodeName(opcode) << ",";
 
     if (opcode == kExprLoop || opcode == kExprIf || opcode == kExprBlock ||