[asm] Fix globals initialized by '-0'

Those globals must have type float instead of int to preserve the sign
bit.

R=ahaas@chromium.org

Bug: chromium:1069173
Change-Id: I9769f47f087aaba94a6172118be44f70adeded0c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2379861Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69609}

src/asmjs/asm-parser.cc

@@ -459,9 +459,15 @@ void AsmJsParser::ValidateModuleVar(bool mutable_variable) {
       if (uvalue > 0x7FFFFFFF) {
         FAIL("Numeric literal out of range");
       }
-      DeclareGlobal(info, mutable_variable,
-                    mutable_variable ? AsmType::Int() : AsmType::Signed(),
-                    kWasmI32, WasmInitExpr(-static_cast<int32_t>(uvalue)));
+      if (uvalue == 0) {
+        // '-0' is treated as float.
+        DeclareGlobal(info, mutable_variable, AsmType::Float(), kWasmF32,
+                      WasmInitExpr(-0.f));
+      } else {
+        DeclareGlobal(info, mutable_variable,
+                      mutable_variable ? AsmType::Int() : AsmType::Signed(),
+                      kWasmI32, WasmInitExpr(-static_cast<int32_t>(uvalue)));
+      }
     } else {
       FAIL("Expected numeric literal");
     }

test/mjsunit/asm/regress-1069173.js

+// Copyright 2020 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 foo() {
+  "use asm";
+  const v = -0;
+  function bar() {
+    return v;
+  }
+  return { d: bar };
+}
+
+var m = foo();
+assertEquals(-Infinity, 1 / m.d());
+assertTrue(%IsAsmWasmCode(foo));

test/mjsunit/mjsunit.status

@@ -345,6 +345,7 @@
   'asm/call-annotation': [SKIP],
   'asm/global-imports': [SKIP],
   'asm/regress-1027595': [SKIP],
+  'asm/regress-1069173': [SKIP],
   'asm/regress-913822': [SKIP],
   'asm/regress-937650': [SKIP],
   'asm/regress-9531': [SKIP],