Added a workaround for undefined behavior.

Note that this patch is not really a *solution*, it is just enough to
make the undefined behavior unobservable. The real fix would be being
much more correct about sizes and signedness in our code base...

BUG=chromium:464657
LOG=n
R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/995743002

Cr-Commit-Position: refs/heads/master@{#27100}

src/compiler/instruction.cc

@@ -337,6 +337,9 @@ std::ostream& operator<<(std::ostream& os,
 }
 
 
+Constant::Constant(int32_t v) : type_(kInt32), value_(v) {}
+
+
 std::ostream& operator<<(std::ostream& os, const Constant& constant) {
   switch (constant.type()) {
     case Constant::kInt32:

src/compiler/instruction.h

@@ -737,7 +737,7 @@ class Constant FINAL {
     kRpoNumber
   };
 
-  explicit Constant(int32_t v) : type_(kInt32), value_(v) {}
+  explicit Constant(int32_t v);
   explicit Constant(int64_t v) : type_(kInt64), value_(v) {}
   explicit Constant(float v) : type_(kFloat32), value_(bit_cast<int32_t>(v)) {}
   explicit Constant(double v) : type_(kFloat64), value_(bit_cast<int64_t>(v)) {}