CDIV deoptimization
===================
This patch implements hints in the disassembler that
aim to assist the user in reading compiler-optimized divisions
by analysing the involved magic number.
Background
==========
Since integer divisions are usually very expensive on most architectures,
compilers try very hard to substitute them with cheaper operations.
One of the more advanced substitutions is described in the book __Hacker's Delight__,
chapter 10.
An actual implementation of the described algorithm in LLVM can be found in the
functions: `TargetLowering::BuildSDIV()` and `APInt::magic()`.
The optimization approximately transforms e.g.
```asm
xor edx, edx
idiv 39
```
into
```asm
mov eax, edi
mov edx, 0xd20d20d3
imul edx
lea eax, [rdx + rdi]
sar edi, 0x1f
sar eax, 5
sub eax, edi
```
Reading the optimized version and __seeing__ the constant 39 seems difficult.
Therefore I try to provide a small hint to the user.
Limitations
===========
* The current implementation only takes the magic number into account,
therefore it may result in false positives.
* Due to the nature of the optimization, the given hint may be off by a power of two.
Fixing this would require to analyse the following shift instructions.
* The hint is only shown in the line containing the magic number.
The user still has to know which of the following instructions belong to the optimization.
TODO
====
* Implement the corresponding analysis for unsigned integers
* Implement the corresponding analysis for 64-bit integers.
* Improve the heuristic by also looking at the next few instructions.
( I don't really know how to iterate over the instructions in the disassember
in a non-deprecated way. Maybe someone can drop me a hint? )
* Implement an exact analysis using the actual dataflow in radeco and use it
to revert the optimization. ( I suppose this is outside the scope of radare )
fixes mentioned in the pr
fixed the Vp issue mentioned in the pr
fixes the mentioned parts
changed reallocation size
Signed-off-by: Riccardo Schirone <sirmy15@gmail.com>
Colours current node in Graphviz output (`ag` command) 'lightblue'.
Add `graph.gv.current` option to config with default to `false`
* White space fixes
Spaces before parens
* Make GV colour configurable
Using existing colours from the palette. Changes boxes from
`lightgray` to `gray` and allows settings for traced boxes, box colour,
and current box colour.
some rework in order to handle mach message as mach_exc_server and alike does
api change in plugin debug, now the function detach receive a pointer to RDebug
trying to deallocate port when are not needed any more
Right now, the telescoping works only one level deep: something points to something. This commit adds recursive telescoping, similar to gdp-peda's.
Sample screenshot: http://i.imgur.com/JsThuTD.png.
Uses hex.depth which is 5 by default
