Hi,

Presently the decision as to whether to completely scalarize an aggregate
or not is made based on MOVE_RATIO. This is an undocumented, and unexpected,
overloading of the target macro.

In this patch we fix this.

First, we we add a new target hook
TARGET_DEFAULT_MAX_TOTAL_SCALARIZATION_SIZE, which returns MOVE_RATIO
by default.

Then we add two new parameters:

  sra-max-total-scalarization-size-Ospeed - The maximum size of aggregate
  to consider when compiling for speed
  sra-max-total-scalarization-size-Osize - The maximum size of aggregate
  to consider when compiling for size.

Set to default to 0.

Finally we wire up SRA to prefer using the parameters, and if it doesn't
find values for them, fallback to the target hook.

Bootstrapped and regression tested for x86, arm and aarch64 with no
issues, I've also thrown a smoke-test of popular small benchmarks at
each platform without seeing meaningful differences (as you would expect).

OK?

Thanks,
James

---
gcc/

2014-08-20  James Greenhalgh  <james.greenhalgh@arm.com>

	* doc/invoke.texi (sra-max-total-scalarization-size-Ospeed): Document.
	(sra-max-total-scalarization-size-Osize): Likewise.
	* doc/tm.texi.in
	(TARGET_DEFAULT_MAX_TOTAL_SCALARIZATION_SIZE): Add hook.
	* doc/tm.texi: Regenerate.
	* params.def (sra-max-total-scalarization-size-Ospeed): New.
	(sra-max-total-scalarization-size-Osize): Likewise.
	* target.def (default_max_total_scalarization_size): New.
	* targhooks.c (default_max_total_scalarization_size): New.
	* targhooks.h (default_max_total_scalarization_size): New.
	* tree-sra.c (get_max_total_scalarization_size): New.
	(analyze_all_variable_accesses): Use it.