https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38470
Andrew Macleod <amacleod at redhat dot com> changed:
What |Removed |Added
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CC| |amacleod at redhat dot com
--- Comment #18 from Andrew Macleod <amacleod at redhat dot com> ---
The code as shown gets generated right off the bat in SSA as
<bb 2> :
_1 = ABS_EXPR <x_2(D)>;
_3 = (unsigned int) _1;
return _3;
which shouldn't even need the Ranger for. globally _1 should be [0, MAX] and I
wouldn't expect any warning...
If you tweak the code so it shows the if structure:
if (x >= 0)
return x ;
return -x;
Then then ranger could help produce the same info:
=========== BB 2 ============
x_3(D) [-INF, +INF] int
<bb 2> :
if (x_3(D) >= 0)
goto <bb 3>; [INV]
else
goto <bb 4>; [INV]
2->3 (T) x_3(D) : [0, +INF] int
2->4 (F) x_3(D) : [-INF, 0xffffffff] int
=========== BB 3 ============
x_3(D) [0, +INF] int
<bb 3> :
_5 = (unsigned int) x_3(D);
// predicted unlikely by early return (on trees) predictor.
goto <bb 5>; [INV]
_5 : [0, 0x7fffffff] unsigned int
=========== BB 4 ============
x_3(D) [-INF, 0xffffffff] int
<bb 4> :
_1 = -x_3(D);
_4 = (unsigned int) _1;
_1 : [1, +INF] int
_4 : [1, 0x7fffffff] unsigned int
=========== BB 5 ============
<bb 5> :
# _2 = PHI <_5(3), _4(4)>
return _2;
_2 : [0, 0x7fffffff] unsigned int
It recognizes that both:
a) _3(D) [0, +INF] int is positive before being "cast" to unsigned int _5
b) _1 is always positive when the conversion to unsigned int is made in BB4.
So the information would be there if one knew what to look for and how to use
it.
