Re: [Qemu-devel] [RFC][PATCH v2 0/4] tcg: enhance code generation quality for qemu_ld/st IRs

[Yeongkyoon Lee]

On 2012년 07월 05일 22:23, Yeongkyoon Lee wrote:
> Summarized feature is as following.
>   - All the changes are wrapped by macro "CONFIG_QEMU_LDST_OPTIMIZATION" and 
> disabled by default.
>   - They are enabled by "configure --enable-ldst-optimization" and need 
> CONFIG_SOFTMMU.
>   - They do not work with CONFIG_TCG_PASS_AREG0 because it looks better apply 
> them after areg0 codes come steady.
>   - Currently, they support only x86 and x86-64 and have been tested with x86 
> and ARM linux targets on x86/x86-64 host platforms.
>   - Build test has been done for all targets.

I'd like to summarize community's feedbacks/observations and propose new 
patch for ldst optimization.

* Feedbacks/observations
1. It needs to work with PASS_AREG0 (CONFIG_TCG_PASS_AREG0).
2. It does not need to be configured by user.
3. It looks good for a target to be ldst-optimized on x86/64 hosts not 
optionally.
4. CONFIG_QEMU_LDST_OPTIMIZATION looks necessary because common code 
(e.g. tcg.h/tcg.c) is used on-x86 hosts and it should support 
non-softmmu targets.
5. It might need two versions of MMU helpers, standard and extended, 
simultaneously because C code might want to call the standard version.

* Modification proposals
1. Apply ldst optimization also when PASS_AREG0 enabled.
2. Make softmmu targets always to use ldst optimization on x86/64 hosts. 
But testing for many targets is an issue...
3. Make target mem(op) helpers to provide extended MMU helpers and 
softmmu_header.h to provide standard MMU helpers.
4. Fix some mistypings and redundant checks.

I'm not sure whether my proposals are feasible, however, I'd like to try 
them.
How do you think about it?

> Yeongkyoon Lee (4):
>    tcg: add declarations and templates of extended MMU helpers
>    tcg: add extended MMU helpers to softmmu targets
>    tcg: add optimized TCG qemu_ld/st generation
>    configure: add CONFIG_QEMU_LDST_OPTIMIZATION for TCG qemu_ld/st
>      optimization
>
>   configure                     |   15 ++
>   softmmu_defs.h                |   13 ++
>   softmmu_template.h            |   51 +++++--
>   target-alpha/mem_helper.c     |   22 +++
>   target-arm/op_helper.c        |   23 +++
>   target-cris/op_helper.c       |   22 +++
>   target-i386/mem_helper.c      |   22 +++
>   target-lm32/op_helper.c       |   23 +++-
>   target-m68k/op_helper.c       |   22 +++
>   target-microblaze/op_helper.c |   22 +++
>   target-mips/op_helper.c       |   22 +++
>   target-ppc/mem_helper.c       |   22 +++
>   target-s390x/op_helper.c      |   22 +++
>   target-sh4/op_helper.c        |   22 +++
>   target-sparc/ldst_helper.c    |   23 +++
>   target-xtensa/op_helper.c     |   22 +++
>   tcg/i386/tcg-target.c         |  328 +++++++++++++++++++++++++++++++++++++++++
>   tcg/tcg.c                     |   12 ++
>   tcg/tcg.h                     |   35 +++++
>   19 files changed, 732 insertions(+), 11 deletions(-)