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Implement __builtin_clzll builtin #206

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Merged
sim642 merged 5 commits into from
Jan 15, 2026
Merged

Implement __builtin_clzll builtin #206

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7fe90da
Implement __builtin_clzll builtin
jprotopopov-ut Apr 17, 2025
2e2ae39
Update testcil.pl with new builtin_clzll test
jprotopopov-ut Jan 14, 2026
7494a3f
Simplify __builtin_clzll implementation
jprotopopov-ut Jan 15, 2026
69a44bc
Only fold constant __builtin_clzll
sim642 Jan 15, 2026
01006dd
Merge branch 'develop' into builtin-clzll-1
sim642 Jan 15, 2026
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22 changes: 22 additions & 0 deletions src/frontc/cabs2cil.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -4752,6 +4752,28 @@ and doExp (asconst: bool) (* This expression is used as a constant *)
prestype := intType
| _ -> ignore (warn "Invalid call to builtin_types_compatible_p");
end
else if fv.vname = "__builtin_clzll" then
begin
(* Constant-fold the argument and see if it is a constant *)
let rec countLeadingZeros (arg: cilint) pos count =
if is_zero_cilint (logand_cilint (shift_right_cilint arg pos) one_cilint) then
match pos with
0 -> count + 1
| _ -> countLeadingZeros arg (pos - 1) (count + 1)
else
count
in
match !pargs with
[ arg ] -> begin
match constFold true arg with
(Const CInt (arg, kind, _)) ->
piscall := false;
pres := integer (countLeadingZeros arg 63 0);
prestype := intType
| _ -> ()
end
| _ -> ignore (warn "Invalid call to __builtin_clzll");
end
end
| _ -> ()
);
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9 changes: 9 additions & 0 deletions test/small1/builtin_clzll.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
struct S1 {
int x : __builtin_choose_expr(__builtin_clzll(0ull) == 64, 1, -1),
: __builtin_choose_expr(__builtin_clzll(~0ull) == 0, 1, -1),
: __builtin_choose_expr(__builtin_clzll(1) == 63, 1, -1),
: __builtin_choose_expr(__builtin_clzll(2) == 62, 1, -1),
: __builtin_choose_expr(__builtin_clzll(4) == 61, 1, -1),
: __builtin_choose_expr(__builtin_clzll(1024) == 53, 1, -1),
: __builtin_choose_expr(__builtin_clzll(1024 * 1024) == 43, 1, -1);
} s1;