[Patch, ARM] New feature to minimize the literal load for armv7-m target

["Terry Guo" <terry dot guo at arm dot com>]

Hi,

This patch intends to minimize the use of literal pool for some armv7-m
targets that have slower speed to load data from flash than to fetch
instruction from flash. The normal literal load instruction is now replaced
by MOVW/MOVT instructions. A new option -mslow-flash-data is created for
this purpose. So far this feature doesn't support PIC code and target that
isn't based on armv7-m.

Tested with GCC regression test on QEMU for cortex-m3. No new regressions.
Is it OK to trunk?

BR,
Terry

2013-11-06  Terry Guo  <terry.guo@arm.com>

                 * doc/invoke.texi (-mslow-flash-data): Document new option.
                 * config/arm/arm.opt (mslow-flash-data): New option.
                 * config/arm/arm-protos.h
(arm_max_const_double_inline_cost): Declare it.
                 * config/arm/arm.h (TARGET_USE_MOVT): Always true when
disable literal pools.
                 (arm_disable_literal_pool): Declare it.
                 * config/arm/arm.c (arm_disable_literal_pool): New
variable.
                 (arm_option_override): Handle new option.
                 (thumb2_legitimate_address_p): Invalid certain address
format.
                 (arm_max_const_double_inline_cost): New function.
                 * config/arm/arm.md (types.md): Include it a little
earlier.
                 (use_literal_pool): New attribute.
                 (enabled): Use new attribute.
                 (split pattern): Replace symbol+offset with MOVW/MOVT.

Attachment: cortex-m-slow-flash-data.txt
Description: Text document