[wasm][asm.js] Permit ternary operator in asm.js returns in some cases.

src/asmjs/asm-typer.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/asmjs/asm-typer.h"
 
 #include <algorithm>
 #include <limits>
 #include <memory>
 #include <string>
@@ skipping 1207 matching lines @@
 
   do {
     if (statements->length() == 0) {
       return_type_ = AsmType::Void();
     } else {
       auto* last_statement = statements->last();
       auto* as_block = last_statement->AsBlock();
       if (as_block != nullptr) {
         statements = as_block->statements();
       } else {
-        // We don't check whether AsReturnStatement() below returns non-null --
-        // we leave that to the ReturnTypeAnnotations method.
-        RECURSE(return_type_ =
-                    ReturnTypeAnnotations(last_statement->AsReturnStatement()));
+        if (auto* ret_statement = last_statement->AsReturnStatement()) {
+          RECURSE(return_type_ =
+                      ReturnTypeAnnotations(ret_statement->expression()));
+        } else {
+          return_type_ = AsmType::Void();
+        }
       }
     }
   } while (return_type_ == AsmType::None());
 
   DCHECK(return_type_->IsReturnType());
 
   for (Declaration* decl : *fun->scope()->declarations()) {
     auto* var_decl = decl->AsVariableDeclaration();
     if (var_decl == nullptr) {
       FAIL(decl, "Functions may only define inner variables.");
@@ skipping 1498 matching lines @@
     FAIL(annotation,
          "Invalid float parameter type annotation - argument to fround is not "
          "a parameter.");
   }
 
   SetTypeOf(src_expr, AsmType::Float());
   return AsmType::Float();
 }
 
 // 5.2 ReturnTypeAnnotations
-AsmType* AsmTyper::ReturnTypeAnnotations(ReturnStatement* statement) {
-  if (statement == nullptr) {
-    return AsmType::Void();
-  }
-
-  auto* ret_expr = statement->expression();
-  if (ret_expr == nullptr) {
-    return AsmType::Void();
-  }
+AsmType* AsmTyper::ReturnTypeAnnotations(Expression* ret_expr) {
+  DCHECK_NOT_NULL(ret_expr);
 
   if (auto* binop = ret_expr->AsBinaryOperation()) {
     if (IsDoubleAnnotation(binop)) {
       return AsmType::Double();
     } else if (IsIntAnnotation(binop)) {
       return AsmType::Signed();
     }
-    FAIL(statement, "Invalid return type annotation.");
+    FAIL(ret_expr, "Invalid return type annotation.");
   }
 
   if (auto* call = ret_expr->AsCall()) {
     if (IsCallToFround(call)) {
       return AsmType::Float();
     }
-    FAIL(statement, "Invalid function call in return statement.");
+    FAIL(ret_expr, "Invalid function call in return statement.");
   }
 
   if (auto* literal = ret_expr->AsLiteral()) {
     int32_t _;
     if (IsLiteralDouble(literal)) {
       return AsmType::Double();
     } else if (IsLiteralInt(literal) && literal->value()->ToInt32(&_)) {
       return AsmType::Signed();
     } else if (literal->IsUndefinedLiteral()) {
       // *VIOLATION* The parser changes
       //
       // return;
       //
       // into
       //
       // return undefined
       return AsmType::Void();
     }
-    FAIL(statement, "Invalid literal in return statement.");
+    FAIL(ret_expr, "Invalid literal in return statement.");
   }
 
   if (auto* proxy = ret_expr->AsVariableProxy()) {
     auto* var_info = Lookup(proxy->var());
 
     if (var_info == nullptr) {
-      FAIL(statement, "Undeclared identifier in return statement.");
+      FAIL(ret_expr, "Undeclared identifier in return statement.");
     }
 
     if (var_info->mutability() != VariableInfo::kConstGlobal) {
-      FAIL(statement, "Identifier in return statement is not const.");
+      FAIL(ret_expr, "Identifier in return statement is not const.");
     }
 
     if (!var_info->type()->IsReturnType()) {
-      FAIL(statement, "Constant in return must be signed, float, or double.");
+      FAIL(ret_expr, "Constant in return must be signed, float, or double.");
     }
 
     return var_info->type();
   }
 
-  FAIL(statement, "Invalid return type expression.");
+  // NOTE: This is not strictly valid asm.js, but is emitted by some versions of
+  // Emscipten.

[Mircea Trofin, 2017/01/26 07:47:27]

Emscripten

[bradn, 2017/01/26 07:50:42]

Done.

+  if (auto* cond = ret_expr->AsConditional()) {
+    AsmType* a;

[Mircea Trofin, 2017/01/26 07:47:27]

init a and b?

[bradn, 2017/01/26 07:50:42]

Done.

+    AsmType* b;
+    RECURSE(a = ReturnTypeAnnotations(cond->then_expression()));
+    if (a->IsA(AsmType::None())) {
+      return a;
+    }
+    RECURSE(b = ReturnTypeAnnotations(cond->else_expression()));
+    if (b->IsA(AsmType::None())) {
+      return b;
+    }
+    if (a->IsExactly(b)) {
+      return a;
+    }
+  }
+
+  FAIL(ret_expr, "Invalid return type expression.");
 }
 
 // 5.4 VariableTypeAnnotations
 // Also used for 5.5 GlobalVariableTypeAnnotations
 AsmType* AsmTyper::VariableTypeAnnotations(
     Expression* initializer, VariableInfo::Mutability mutability_type) {
   if (auto* literal = initializer->AsLiteral()) {
     if (IsLiteralDouble(literal)) {
       SetTypeOf(initializer, AsmType::Double());
       return AsmType::Double();
@@ skipping 116 matching lines @@
          "Heap view creation parameter should be the module's heap parameter.");
   }
 
   DCHECK(heap_view_info->type()->IsA(AsmType::Heap()));
   return heap_view_info->type();
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8