[asm.js] Fix undefined behavior with float32 constants.

R=jkummerow@chromium.org
TEST=mjsunit/asm/regress-937650
BUG=chromium:937650

Change-Id: I9a46fcce68cf1b5c424539aad2f78fbcd30cf9b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1505458Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60080}

src/asmjs/asm-parser.cc

@@ -13,6 +13,7 @@
 #include "src/asmjs/asm-types.h"
 #include "src/base/optional.h"
 #include "src/base/overflowing-math.h"
+#include "src/conversions-inl.h"
 #include "src/flags.h"
 #include "src/parsing/scanner.h"
 #include "src/wasm/wasm-limits.h"
@@ -520,7 +521,7 @@ void AsmJsParser::ValidateModuleVarFromGlobal(VarInfo* info,
       dvalue = -dvalue;
     }
     DeclareGlobal(info, mutable_variable, AsmType::Float(), kWasmF32,
-                  WasmInitExpr(static_cast<float>(dvalue)));
+                  WasmInitExpr(DoubleToFloat32(dvalue)));
   } else if (CheckForUnsigned(&uvalue)) {
     dvalue = uvalue;
     if (negate) {

test/mjsunit/asm/regress-937650.js

+// Copyright 2019 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.
+
+// Flags: --allow-natives-syntax
+
+function Module(stdlib) {
+  "use asm";
+  var fround = stdlib.Math.fround;
+  // The below constant is outside the range of representable {float} values.
+  const infinity = fround(1.7976931348623157e+308);
+  function f() {
+    return infinity;
+  }
+  return { f: f };
+}
+
+var m = Module(this);
+assertEquals(Infinity, m.f());
+assertTrue(%IsAsmWasmCode(Module));

test/mjsunit/mjsunit.status

@@ -361,6 +361,7 @@
   'asm/call-annotation': [SKIP],
   'asm/global-imports': [SKIP],
   'asm/regress-913822': [SKIP],
+  'asm/regress-937650': [SKIP],
   'asm/return-types': [SKIP],
   'regress/regress-599719': [SKIP],
   'regress/regress-6196': [SKIP],