Hi,
Thanks for your comments.
Sorry for this useless patch. considering the stop instruction it does not
add much; I was not aware of this feature and needed something similar.
The manual breakpoints did not have a string description feature, but added
an enable / disable feature and some simple counter information.
I also found a few interesting issues while reading the "stop" feature code:
- The way stops are generated does not look very safe:
*void Assembler::stop(const char* msg) { *
* emit(15 << 28 | ((intptr_t) msg));*
*[...]*
*}*
*
*
The Simulator decodes the stop and gets the string address with:
*const char* str = (const char*)(instr->InstructionBits() & 0x0fffffff);*
Shouldn't there at least be a check when we generate the stop?
- Also the stop encoding could match a BLX with an immediate value!!!
Luckily it is defined but never used. I did not look in details at how the
Simulator would handle this.
*void Assembler::blx(int branch_offset) { // v5 and above*
*[...]*
* emit(15 << 28 | B27 | B25 | h | (imm24 & Imm24Mask));*
*}*
- There also seems to be something wrong
with Simulator::DecodeUnconditional() . It looks like no load halfword
instruction in the ARM ISA actually use the special_condition code...
If you are interested, I could have a look at all this, fix what needs to
be, and at the same time merge the functionalities and implementation of
stop and "manual breakpoints". I could also add some documentation to the
wiki about debugging with the ARM Simulator. It would maybe save other
people from later trying to write another similar debug feature.
Regards,
Alexandre
On Tue, Sep 28, 2010 at 6:18 PM, <[email protected]> wrote:
> Thanks for the patch.
>
> What does this add to what is already there with the stop instruction? I
> have
> been doing lots of debugging of the generated arm code on the simulator
> using
> the stop instruction. Here is a session after adding a stop("inlined load")
> call
> just before an inlined load:
>
> Simulator hit inlined load
> 0xf53880f4 e3110001 tst r1, #1
> sim> disasm
> 0xf53880f4 e3110001 tst r1, #1
> 0xf53880f8 0a000089 beq +556 -> 0xf5388324
> 0xf53880fc e5117001 ldr r7, [r1, #-1]
> 0xf5388100 e59f92a8 ldr r9, [pc, #+680]
> 0xf5388104 e1570009 cmp r7, r9
> 0xf5388108 1a000085 bne +540 -> 0xf5388324
> 0xf538810c e5911000 ldr r1, [r1, #+0]
> 0xf5388110 e1807001 orr r7, r0, r1
> 0xf5388114 e3170001 tst r7, #1
> 0xf5388118 0a000003 beq +20 -> 0xf538812c
> sim> p r1
> r1: 0xf600e229 -167714263
> sim> po r1
> r1:
> 0xf600e229: [JSObject]
> - map = 0xf535cb81
> - prototype = 0xf600dbd1
> {
> #length: 0xf539ed51 <Proxy> (callback)
> 0: 0xf539fdf1 <String[5]: isNaN>
> 1: 0xf53c0a01 <JS Function GlobalIsNaN>
> 2: 0xf539fe05 <String[8]: isFinite>
> 3: 0xf53c0a21 <JS Function GlobalIsFinite>
> 4: 0xf539fe19 <String[8]: parseInt>
> 5: 0xf53c0a41 <JS Function GlobalParseInt>
> 6: 0xf539fe2d <String[10]: parseFloat>
> 7: 0xf53c0a61 <JS Function GlobalParseFloat>
> 8: 0xf539c2cd <String[4]: eval>
> 9: 0xf53c0a81 <JS Function GlobalEval>
> 10: 0xf539fe45 <String[10]: execScript>
> 11: 0xf53c0aa1 <JS Function GlobalExecScript>
> }
>
> sim> stepi
> 0xf53880f8 0a000089 beq +556 -> 0xf5388324
> sim> stepi
> 0xf53880fc e5117001 ldr r7, [r1, #-1]
> sim> c
> Simulator hit inlined load
> 0xf53880f4 e3110001 tst r1, #1
> sim>
>
>
>
>
> http://codereview.chromium.org/3440028/show
>
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