* Linaro

Continued trying to understand lower-subreg and its impact on ARM optimization. After much staring at RTL dumps and trying to minimize test cases from large code bases I've not found an example of code where disabling the lowering of pseudo-to-pseudo copies made the code larger for anything other than unfortunate random knock-on effects (such as no longer being able to use 16-bit thumb1 opcodes). I posted a message to this effect on the gcc list, and I'll try benchmarking a patch for this next week.

In the process of looking at lower-subreg, discovered a silly missed-optimization bug with many DImode operations, and reported it to GCC Bugzilla as pr53189.