Convert float64 to float32 when coerced with a heapf32 assignment.

BUG= https://code.google.com/p/v8/issues/detail?id=4203
TEST=mjsunit/asm-wasm
R=titzer@chromium.org,aseemgarg@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1749233002

Cr-Commit-Position: refs/heads/master@{#34404}

src/wasm/asm-wasm-builder.cc

@@ -694,6 +694,12 @@ class AsmWasmBuilderImpl : public AstVisitor {
     is_set_op_ = true;
     RECURSE(Visit(expr->target()));
     DCHECK(!is_set_op_);
+    // Assignment to heapf32 from float64 converts.
+    if (TypeOf(expr->value()) == kAstF64 && expr->target()->IsProperty() &&
+        expr->target()->AsProperty()->obj()->bounds().lower->Is(
+            cache_.kFloat32Array)) {
+      current_function_builder_->Emit(kExprF32ConvertF64);
+    }
     RECURSE(Visit(expr->value()));
     if (in_init) {
       UnLoadInitFunction();

test/cctest/test-asm-validator.cc

@@ -2348,3 +2348,21 @@ TEST(Imports) {
   }
   CHECK_TYPES_END
 }
+
+TEST(StoreFloatFromDouble) {
+  CHECK_FUNC_TYPES_BEGIN(
+      "function bar() { f32[0] = 0.0; }\n"
+      "function foo() { bar(); }") {
+    CHECK_EXPR(FunctionLiteral, FUNC_V_TYPE) {
+      CHECK_EXPR(Assignment, Bounds(cache.kAsmDouble)) {
+        CHECK_EXPR(Property, Bounds::Unbounded()) {
+          CHECK_VAR(f32, Bounds(cache.kFloat32Array));
+          CHECK_EXPR(Literal, Bounds(cache.kAsmFixnum));
+        }
+        CHECK_EXPR(Literal, Bounds(cache.kAsmDouble));
+      }
+    }
+    CHECK_SKIP();
+  }
+  CHECK_FUNC_TYPES_END
+}

test/mjsunit/wasm/asm-wasm.js

@@ -1433,6 +1433,24 @@ TestForeignVariables();
 });  // TODO(bradnelson): Enable when Math.fround implementation lands.
 
 
+(function TestDoubleToFloatAssignment() {
+  function Module(stdlib, foreign, heap) {
+    "use asm";
+    var HEAPF32 = new stdlib.Float32Array(heap);
+    var fround = stdlib.Math.fround;
+    function func() {
+      var a = 1.23;
+      HEAPF32[0] = a;
+      return +HEAPF32[0];
+    }
+    return {func: func};
+  }
+
+  var m = _WASMEXP_.instantiateModuleFromAsm(Module.toString());
+  assertEquals(1.23, m.func());
+});
+
+
 (function TestIntegerMultiplyBothWays() {
   function Module(stdlib, foreign, heap) {
     "use asm";