https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112949
Bug ID: 112949
Summary: evrp produces incorrect range for __builtin_clz
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kristerw at gcc dot gnu.org
Target Milestone: ---
The evrp pass generates incorrect ranges for __builtin_clz when it is called
within a function named __builtin_clz. While calling it in this manner seems
questionable, two relatively recent tests in the testsuite (gcc.dg/pr100521.c
and gcc.dg/pr100790.c) suggest that gcc should handle this.
The test case gcc.dg/pr100790.c is as follows:
__builtin_clz(int x) { x ? __builtin_clz(x) : 32; }
Compiling this for x86_64 using -O3 -fpermissive results in the evrp IR:
Global Exported: iftmp.0_3 = [irange] int [1, 31]
__attribute__((nothrow, leaf, const))
int __builtin_clz (int x)
{
int iftmp.0_3;
<bb 2> :
if (x_1(D) != 0)
goto <bb 3>; [INV]
else
goto <bb 4>; [INV]
<bb 3> :
iftmp.0_3 = __builtin_clz (x_1(D));
<bb 4> :
return;
}
The range for iftmp.0_3 (which is an internal call to CFN_BUILT_IN_CLZ) should
be [0, 31], not [1, 31].
