[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken since r14-1455
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722 Jakub Jelinek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #6 from Jakub Jelinek --- Fixed.
[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken since r14-1455
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722 --- Comment #5 from GCC Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:09df058a09f888daad26fa80634068b38b4ad04d commit r14-8776-g09df058a09f888daad26fa80634068b38b4ad04d Author: Jakub Jelinek Date: Sat Feb 3 14:38:27 2024 +0100 wide-int: Fix up wi::bswap_large [PR113722] Since bswap has been converted from a method to a function we miscompile the following testcase. The problem is the assumption that the passed in len argument (number of limbs in the xval array) is the upper bound for the bswap result, which is true only if precision is <= 64. If precision is larger than that, e.g. 128 as in the testcase, if the argument has only one limb (i.e. 0 to ~(unsigned HOST_WIDE_INT) 0), the result can still need 2 limbs for that precision, or generally BLOCKS_NEEDED (precision) limbs, it all depends on how many least significant limbs of the operand are zero. bswap_large as implemented only cleared len limbs of result, then swapped the bytes (invoking UB when oring something in all the limbs above it) and finally passed len to canonize, saying that more limbs aren't needed. The following patch fixes it by renaming len to xlen (so that it is clear it is X's length), using it solely for safe_uhwi argument when we attempt to read from X, and using new len = BLOCKS_NEEDED (precision) instead in the other two spots (i.e. when clearing the val array, turned it also into memset, and in canonize argument). wi::bswap asserts it isn't invoked on widest_int, so we are always invoked on wide_int or similar and those have preallocated result sized for the corresponding precision (i.e. BLOCKS_NEEDED (precision)). 2024-02-03 Jakub Jelinek PR middle-end/113722 * wide-int.cc (wi::bswap_large): Rename third argument from len to xlen and adjust use in safe_uhwi. Add len variable, set it to BLOCKS_NEEDED (precision) and use it for clearing of val and as canonize argument. Clear val using memset instead of a loop. * gcc.dg/pr113722.c: New test.
[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken since r14-1455
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722 --- Comment #4 from Jakub Jelinek --- Created attachment 57296 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57296=edit gcc14-pr113722.patch Untested fix.
[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken since r14-1455
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722
Jakub Jelinek changed:
What|Removed |Added
Summary|[14 Regression] Constant|[14 Regression] Constant
|folding of |folding of
|__builtin_bswap128 is |__builtin_bswap128 is
|broken |broken since r14-1455
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Priority|P3 |P1
--- Comment #3 from Jakub Jelinek ---
Anyway, at -O0
int
main ()
{
unsigned __int128 a = __builtin_bswap128 ((unsigned __int128) 2);
unsigned __int128 b = 2;
unsigned __int128 c = __builtin_bswap128 (b);
if (a != c)
__builtin_abort ();
}
regressed with r14-1455-g0ede6b5ad77c4791a513ab312b9e278dafc2bff9
I'll have a look.
[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #2 from Jakub Jelinek --- The #c0 testcase is broken, res >> 64 has still __uint128_t type, so you shouldn't pass it to %ld format specifier.
[Bug middle-end/113722] [14 Regression] Constant folding of __builtin_bswap128 is broken
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113722
Andrew Pinski changed:
What|Removed |Added
Component|regression |middle-end
Ever confirmed|0 |1
Last reconfirmed||2024-02-02
Summary|Folding of |[14 Regression] Constant
|__builtin_bswap128 doesn't |folding of
|work anymore|__builtin_bswap128 is
||broken
Keywords||wrong-code
Status|UNCONFIRMED |NEW
Target Milestone|--- |14.0
--- Comment #1 from Andrew Pinski ---
Simplified testcase:
```
#define constant 2
int main() {
__uint128_t res = __builtin_bswap128 ((__uint128_t)constant);
__uint128_t t = constant;
__uint128_t res1 = __builtin_bswap128 (t);
if (res != res1)
__builtin_abort();
}
```
