[PATCH] Add -mno-r11 option to suppress load of ppc64 static chain in indirect calls

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

This patch adds an option to not load the static chain (r11) for 64-bit PowerPC
calls through function pointers (or virtual function).  Most of the languages
on the PowerPC do not need the static chain being loaded when called, and
adding this instruction can slow down code that calls very short functions.

In addition, if the function does not call alloca, setjmp or deal with
exceptions where the stack is modified, the compiler can move the store of the
TOC value for the current function to the prologue of the function, rather than
at each call site.

The effect of these patches is to speed up 464.h264ref in the Spec 2006
benchmark by about 7% if -mno-r11 is used, and 5% if it is not used (but the
save of the TOC register is hoisted).  I believe this is due to the load of the
current function's TOC (r2) having to wait until the store queue is drained
with the store just before the call.

Unfortunately, I do see a 3% slowdown in 429.mcf, which I don't know what the
cause is.

I have bootstraped the compiler and saw that there were no regressions in make
check.  Is it ok to install in the trunk?

[gcc]
2011-07-06  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/rs6000-protos.h (rs6000_call_indirect_aix): New
	declaration.
	(rs6000_save_toc_in_prologue_p): Ditto.

	* config/rs6000/rs6000.opt (-mr11): New switch to disable loading
	up the static chain (r11) during indirect function calls.
	(-msave-toc-indirect): New undocumented debug switch.

	* config/rs6000/rs6000.c (struct machine_function): Add
	save_toc_in_prologue field to note whether the prologue needs to
	save the TOC value in the reserved stack location.
	(rs6000_emit_prologue): Use TOC_REGNUM instead of 2.  If we need
	to save the TOC in the prologue, do so.
	(rs6000_trampoline_init): Don't allow creating AIX style
	trampolines if -mno-r11 is in effect.
	(rs6000_call_indirect_aix): New function to create AIX style
	indirect calls, adding support for -mno-r11 to suppress loading
	the static chain, and saving the TOC in the prologue instead of
	the call body.
	(rs6000_save_toc_in_prologue_p): Return true if we are saving the
	TOC in the prologue.

	* config/rs6000/rs6000.md (STACK_POINTER_REGNUM): Add more fixed
	register numbers.
	(TOC_REGNUM): Ditto.
	(STATIC_CHAIN_REGNUM): Ditto.
	(ARG_POINTER_REGNUM): Ditto.
	(SFP_REGNO): Delete, unused.
	(TOC_SAVE_OFFSET_32BIT): Add constants for AIX TOC save and
	function descriptor offsets.
	(TOC_SAVE_OFFSET_64BIT): Ditto.
	(AIX_FUNC_DESC_TOC_32BIT): Ditto.
	(AIX_FUNC_DESC_TOC_64BIT): Ditto.
	(AIX_FUNC_DESC_SC_32BIT): Ditto.
	(AIX_FUNC_DESC_SC_64BIT): Ditto.
	(ptrload): New mode attribute for the appropriate load of a
	pointer.
	(call_indirect_aix32): Delete, rewrite AIX indirect function
	calls.
	(call_indirect_aix64): Ditto.
	(call_value_indirect_aix32): Ditto.
	(call_value_indirect_aix64): Ditto.
	(call_indirect_nonlocal_aix32_internal): Ditto.
	(call_indirect_nonlocal_aix32): Ditto.
	(call_indirect_nonlocal_aix64_internal): Ditto.
	(call_indirect_nonlocal_aix64): Ditto.
	(call): Rewrite AIX indirect function calls.  Add support for
	eliminating the static chain, and for moving the save of the TOC
	to the function prologue.
	(call_value): Ditto.
	(call_indirect_aix<ptrsize>): Ditto.
	(call_indirect_aix<ptrsize>_internal): Ditto.
	(call_indirect_aix<ptrsize>_internal2): Ditto.
	(call_indirect_aix<ptrsize>_nor11): Ditto.
	(call_value_indirect_aix<ptrsize>): Ditto.
	(call_value_indirect_aix<ptrsize>_internal): Ditto.
	(call_value_indirect_aix<ptrsize>_internal2): Ditto.
	(call_value_indirect_aix<ptrsize>_nor11): Ditto.
	(call_nonlocal_aix32): Relocate in the rs6000.md file.
	(call_nonlocal_aix64): Ditto.

	* doc/invoke.texi (RS/6000 and PowerPC Options): Add -mr11 and
	-mno-r11 documentation.
[gcc/testsuite]
2011-07-06  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* gcc.target/powerpc/no-r11-1.c: New test for -mr11, -mno-r11.
	* gcc.target/powerpc/no-r11-2.c: Ditto.
	* gcc.target/powerpc/no-r11-3.c: Ditto.

-- 
Michael Meissner, IBM
5 Technology Place Drive, M/S 2757, Westford, MA 01886-3141, USA
meissner@linux.vnet.ibm.com	fax +1 (978) 399-6899

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