[llvm-commits] [llvm] r78701 - in /llvm/trunk/lib/Target/ARM: ARMBaseInstrInfo.cpp ARMInstrThumb2.td

[Jim Grosbach]

On Aug 13, 2009, at 1:55 AM, Evan Cheng wrote:

>>
>> ----------------------------------------------------------------------=
>> ==//
>> +// SJLJ Exception handling intrinsics
>> +//   eh_sjlj_setjmp() is a three instruction sequence to store the
>> return
>
> 3 instructions?
>

Oops. Fixed.

>> +//   address and save #0 in R0 for the non-longjmp case.
>> +//   Since by its nature we may be coming from some other function
>> to get
>> +//   here, and we're using the stack frame for the containing
>> function to
>> +//   save/restore registers, we can't keep anything live in regs
>> across
>> +//   the eh_sjlj_setjmp(), else it will almost certainly have been
>> tromped upon
>> +//   when we get here from a longjmp(). We force everthing out of
>> registers
>> +//   except for our own input by listing the relevant registers in
>> Defs. By
>> +//   doing so, we also cause the prologue/epilogue code to actively
>> preserve
>> +//   all of the callee-saved resgisters, which is exactly what we
>> want.
>> +let Defs =
>> +  [ R0,  R1,  R3,  R4,  R5,  R6,  R7,  R8,  R9,  R10, R11, R12, LR,
>> +    D0,  D2,  D3,  D4,  D5,  D6,  D7,  D8,  D9,  D10, D11, D12,
>> D13, D14, D15,
>> +    D16, D17, D18, D19, D20, D21, D22, D23, D24, D25, D26, D27,
>> D28, D29, D30,
>> +    D31 ] in {
>> +  def t2Int_eh_sjlj_setjmp : Thumb2XI<(outs), (ins GPR:$src),
>> +                               AddrModeNone, SizeSpecial,
>> NoItinerary,
>> +                               "str.w sp, [$src, #+8] @ eh_setjmp
>> begin\n"
>> +                               "\tadr ip, 0f\n"
>> +                               "\torr ip, #1\n"
>> +                               "\tstr.w ip, [$src, #+4]\n"
>> +                               "\tmovs r0, #0\n"
>> +                               "\tb 1f\n"
>> +                               "0:\tmovs r0, #1 @ eh_setjmp end\n"
>> +                               "1:\n", "",
>> +                               [(set R0, (ARMeh_sjlj_setjmp GPR:
>> $src))]>;
>
> More questions. What do "0f" "1f" mean?  Can we generate multiple
> labels like 0: 1: in the same function? Can there be multiple
> Int_eh_sjlj_setjmp in a function? Does it make sense to add a id
> operand to the instruction so we can print out unique labels?
>

These are assembler numeric labels designed for quick temporary use  
like this.

http://developer.apple.com/DOCUMENTATION/DeveloperTools/Reference/Assembler/020-Assembly_Language_Syntax/asm_syntax.html#//apple_ref/doc/uid/TP30000821-TPXREF106

> One more thing. The '\n' after '1:' is not needed.
>

True. I'll remove it.

> Evan
>
>> +}
>> +
>> +
>> +
>> +//
>> =
>> =
>> =
>> ----------------------------------------------------------------------=
>> ==//
>> // Control-Flow Instructions
>> //
>>
>>
>>
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