On Thu, 1 Mar 2018, Allan, Bruce W wrote:
>
> We have a macro that takes a right-justified contiguous set of bits and
> shifts it left to create a bitmask:
>
>
>
> #define FOO(m, s) (m) << (s)
>
>
>
> where m is in hex and s is an integer. I’d like to transform occurrences of
> it to the Linux kernel’s GENMASK(high, low) macro (which creates a
> contiguous bitmask starting at bit position low and ending at position
> high), but am having problems trying to figure out how to do that.
>
>
>
> For example, I’d like to transform:
>
> #define BITMASK_A FOO(0x3F, 4)
> /* 0x3F0 */
>
> to
>
> #define BITMASK_A GENMASK(9, 4) /*
> 0x3F0 */
>
>
>
> The value s in FOO() is the same as the value low in GENMASK(), but the
> value high in GENMASK() must be calculated from the values m and s in
> FOO(). One calculation would be to use the hamming weight (hweight) such as
> hweight(m) + s – 1. My Python-foo is non-existent but I have found online
> an example for calculating the hamming weight with the Python script ‘def
> hweight(n): return bin(n).count("1")’. Is it possible to use this (or
> another) Python script in a Coccinelle script to do this transform, and if
> so, what would that look like? If the transform cannot use Python, is there
> another suggestion?
I think that you can follow the model of the following code
(demos/pythontococci.cocci). Let me know if it is not clear.
julia
@a@
identifier x;
@@
foo(x);
@script:python b@
x << a.x;
y;
z;
@@
print y
coccinelle.y = x
coccinelle.z = "something"
print y
@c@
identifier b.y;
identifier b.z;
identifier a.x;
@@
- bar();
+ matched_bar(y,z,x);_______________________________________________
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