[wasm] Detect unrepresentability in the float32-to-int32 conversion correctly on arm.

test/cctest/compiler/test-run-machops.cc

Index: test/cctest/compiler/test-run-machops.cc
diff --git a/test/cctest/compiler/test-run-machops.cc b/test/cctest/compiler/test-run-machops.cc
index 685918af7d974065ca82c1f59323e37a2ad686dc..aba0700306d0b3beb4949ce91872118b80671de6 100644
--- a/test/cctest/compiler/test-run-machops.cc
+++ b/test/cctest/compiler/test-run-machops.cc
@@ -4030,25 +4030,20 @@ TEST(RunTruncateFloat32ToInt32) {
 TEST(RunTruncateFloat32ToUint32) {
   BufferedRawMachineAssemblerTester<uint32_t> m(MachineType::Float32());
   m.Return(m.TruncateFloat32ToUint32(m.Parameter(0)));
-  {
     FOR_UINT32_INPUTS(i) {
       volatile float input = static_cast<float>(*i);
       // This condition on 'input' is required because
-      // static_cast<float>(std::numeric_limits<uint32_t>::max()) results in a
-      // value outside uint32 range.
-      if (input < static_cast<float>(std::numeric_limits<uint32_t>::max())) {
+      // static_cast<float>(UINT32_MAX) results in a value outside uint32 range.
+      if (input < (static_cast<float>(static_cast<uint64_t>(UINT32_MAX) + 1))) {

[titzer, 2016/06/30 10:55:26]

Why don't we just spell out the constant as a float instead of all these static
casts? I am not sure if the C++ compiler has any leeway when casting out of the
representable range...I don't trust it.

[ahaas, 2016/06/30 12:02:27]

I wrote it this way because I think it is more readable and robust than spelling
it out as a float. The C++ should not have any leeway here because all values
here are in representable range: UINT32_MAX and also (UINT32_MAX + 1) are within
uint64 range, and (UINT32_MAX + 1) is representable as float.

         CHECK_EQ(static_cast<uint32_t>(input), m.Call(input));
       }
     }
-  }
-  {
-    FOR_FLOAT32_INPUTS(i) {
-      if (*i <= static_cast<float>(std::numeric_limits<uint32_t>::max()) &&
-          *i >= static_cast<float>(std::numeric_limits<uint32_t>::min())) {
-        CHECK_FLOAT_EQ(static_cast<uint32_t>(*i), m.Call(*i));
+    FOR_FLOAT32_INPUTS(j) {
+      if (*j < (static_cast<float>(static_cast<uint64_t>(UINT32_MAX) + 1)) &&
+          *j > -1) {
+        CHECK_FLOAT_EQ(static_cast<uint32_t>(*j), m.Call(*j));
       }
     }
-  }
 }