llvm dev - Sep 2011 - [LLVMdev] Reserved call frame

Hello,

i am trying to disable reserved call frame from the x86 backend, by 
setting hasReservedCallFrame function, in
lib/Target/X86/X86RegisterInfo.cpp to always return false. When doing 
this i get the correct frame size,
and the sub/add rsp instructions around the call correctly, but it seems 
that the offsets from rsp are not
correctly updated between the sub instruction and the call.

Is this some kind of a bug, or i should make more changes to disable 
reserved call frame ?

Here is a piece of the output of the testcase with the reservedCallFrame 
enabled:

# BB#26:                                # %L51
     movq    536(%rsp), %rbp
     movq    $-5, 536(%rsp)
     movq    552(%rsp), %rsi
     movq    560(%rsp), %rdx
     movq    544(%rsp), %rcx
     movq    %rdi, (%rsp)
     movq    $2, 8(%rsp)
     sarq    $4, %rbp
     leaq *128*(%rsp), %rdi
     movq    %rbp, %r8
     movq *40*(%rsp), %r9           # 8-byte Reload
     callq    bs_put_big_integer     # a function call with 5 arguments
     movq    128(%rsp), %rax
     movq    136(%rsp), %rcx
     cmpq    $0, 144(%rsp)
     movq    %rcx, 560(%rsp)
     movq    %rax, 552(%rsp)
     jne    .LBB0_30

And the same piece of code  with reservedCallFrame disabled:

# BB#26:                                # %L51
     movq    520(%rsp), %rbp
     movq    $-5, 520(%rsp)
     movq    536(%rsp), %rsi
     movq    544(%rsp), %rdx
     movq    528(%rsp), %rcx
     subq *$16*, %rsp
     movq    %rdi, (%rsp)
     movq    $2, 8(%rsp)
     sarq    $4, %rbp
     leaq *112*(%rsp), %rdi
     movq    %rbp, %r8
     movq *24*(%rsp), %r9           # 8-byte Reload
     callq    bs_put_big_integer    # a function call with 5 arguments
     addq    $*16*, %rsp
     movq    112(%rsp), %rax
     movq    120(%rsp), %rcx
     cmpq    $0, 128(%rsp)
     movq    %rcx, 544(%rsp)
     movq    %rax, 536(%rsp)
     jne    .LBB0_30

Thanks
Chris Stavrakakis
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110909/125afa85/attachment.html>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: gen2_3-no_reserved_cf.s
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110909/125afa85/attachment.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: gen2_3-vanilla.s
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110909/125afa85/attachment-0001.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: gen2_3.ll
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110909/125afa85/attachment-0002.ksh>

Hello
> Is this some kind of a bug, or i should make more changes to disable
> reserved call frame ?
I believe that the prologue / epilogue emission code and callframe
setup / destroy node elimination code assumes the particular "type" of
call frame and simple not implemented for other type. So, you have to
implement it by yourself.

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University