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Re: [Qemu-devel] [PULL 5/7] tcg: Add mmu helpers that take a return addr
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PULL 5/7] tcg: Add mmu helpers that take a return address argument |
Date: |
Tue, 27 Aug 2013 07:53:56 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 |
On 08/27/2013 03:46 AM, Aurelien Jarno wrote:
> On the other hand calling the helper is the exception more than the
> rule (that's why they have been moved at the end of the TB), so we
> should not look to much at generating fast code, but rather small code
> in order to use the caches (both TB and CPU caches) more efficiently.
>
> Therefore even on x86, if we move the -1 at the helper level, it should
> be possible to use a tail call for the stores, something like:
>
> mov %r14,%rdi
> mov %ebx,%edx
> xor %ecx,%ecx
> lea -0x10f(%rip),%r8 # 0x7f2541a6f69a
> pushq %r8
> jmpq 0x7f25526757a0
>
> Instead of:
>
> mov %r14,%rdi
> mov %ebx,%edx
> xor %ecx,%ecx
> lea -0x10f(%rip),%r8 # 0x7f2541a6f69a
> callq 0x7f25526757a0
> jmpq 0x7f2541a6f69b
Fair enough. I'll have a go at some follow-ups then.
r~
- [Qemu-devel] [PULL 0/7] Improve tcg ldst optimization, Richard Henderson, 2013/08/26
- [Qemu-devel] [PULL 1/7] tcg: Tidy generated code for tcg_outN, Richard Henderson, 2013/08/26
- [Qemu-devel] [PULL 2/7] tcg-i386: Add and use tcg_out64, Richard Henderson, 2013/08/26
- [Qemu-devel] [PULL 3/7] tcg-i386: Try pc-relative lea for constant formation, Richard Henderson, 2013/08/26
- [Qemu-devel] [PULL 4/7] tcg-i386: Tidy qemu_ld/st slow path, Richard Henderson, 2013/08/26
- [Qemu-devel] [PULL 5/7] tcg: Add mmu helpers that take a return address argument, Richard Henderson, 2013/08/26
Re: [Qemu-devel] [PULL 5/7] tcg: Add mmu helpers that take a return address argument, Peter Maydell, 2013/08/26
[Qemu-devel] [PULL 6/7] tcg: Tidy softmmu_template.h, Richard Henderson, 2013/08/26
[Qemu-devel] [PULL 7/7] tcg-i386: Use new return-argument ld/st helpers, Richard Henderson, 2013/08/26