Bug 1564125 - Part 1: Don't call into the runtime for negative zero in LDoubleToString. r=nbp

The string representation of negative zero is equal to the one for positive zero, so there's no
need to call into the runtime for that case.

Differential Revision: https://phabricator.services.mozilla.com/D37259

--HG--
extra : moz-landing-system : lando

js/src/jit/CodeGenerator.cpp

@@ -1569,7 +1569,7 @@ void CodeGenerator::visitDoubleToString(LDoubleToString* lir) {
       lir, ArgList(input), StoreRegisterTo(output));
 
   // Try double to integer conversion and run integer to string code.
-  masm.convertDoubleToInt32(input, temp, ool->entry(), true);
+  masm.convertDoubleToInt32(input, temp, ool->entry(), false);
   emitIntToString(temp, output, ool->entry());
 
   masm.bind(ool->rejoin());