https://gcc.gnu.org/g:2149eda29e2628d31faf44da060139a856c47b3f
commit r16-7277-g2149eda29e2628d31faf44da060139a856c47b3f Author: Jakub Jelinek <[email protected]> Date: Wed Feb 4 11:25:01 2026 +0100 bitint: Don't try to extend PHI in the min_prec == prec case [PR122689] The following testcase is miscompiled on aarch64-linux, the problem is that the PHI argument is lowered to VIEW_CONVERT_EXPR<unsigned long[196]>(y) = VIEW_CONVERT_EXPR<unsigned long[196]>(*.LC0); MEM <unsigned long[1]> [(unsigned _BitInt(12419) *)&y + 1568B] = {}; on the edge, where for aarch64 unsigned _BitInt(12419) the size of the type is already 1568 bytes (aka 196 DImode limbs, 98 TImode ABI limbs), so the fir stmt copies everything and the second stmt clobbers random unrelated memory after it. Usually when min_prec == prec (otherwise we guarantee that min_prec is either 0, or a single limb (which doesn't have padding bits) or something without any padding bits (multiple of abi_limb_prec)) we take the if (c) { if (VAR_P (v1) && min_prec == prec) { tree v2 = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (v1), c); g = gimple_build_assign (v1, v2); gsi_insert_on_edge (e, g); edge_insertions = true; break; } path and need nothing else, but in this case v1 is a PARM_DECL, so we need to take the code path with VCE on the lhs side as well. But after the assignment we fall through into the handling of the extension, but for min_prec == prec that isn't needed and is actually harmful, we've already copied everything and the code later on assumes there are no padding bits and uses just TYPE_SIZE_UNIT. So, this patch just avoids the rest after we've copied all the bits for min_prec == prec. 2026-02-04 Jakub Jelinek <[email protected]> PR middle-end/122689 * gimple-lower-bitint.cc (gimple_lower_bitint): For the PHI handling if min_prec == prec, break after emitting assignment from c. * gcc.dg/bitint-127.c: New test. Diff: --- gcc/gimple-lower-bitint.cc | 5 +++++ gcc/testsuite/gcc.dg/bitint-127.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc index 9d027c6a6a1a..b33a5b43dc86 100644 --- a/gcc/gimple-lower-bitint.cc +++ b/gcc/gimple-lower-bitint.cc @@ -7804,6 +7804,11 @@ gimple_lower_bitint (void) vtype, c)); } gsi_insert_on_edge (e, g); + if (min_prec == prec) + { + edge_insertions = true; + break; + } } if (ext == 0) { diff --git a/gcc/testsuite/gcc.dg/bitint-127.c b/gcc/testsuite/gcc.dg/bitint-127.c new file mode 100644 index 000000000000..b0f69bdc2d8c --- /dev/null +++ b/gcc/testsuite/gcc.dg/bitint-127.c @@ -0,0 +1,28 @@ +/* PR middle-end/122689 */ +/* { dg-do run { target { bitint } } } */ +/* { dg-options "-O" } */ + +#if __BITINT_MAXWIDTH__ >= 12419 +const _BitInt(12419) n = 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 fe61794a07a066080d1af3d90121a09c62583512a75df831bfbd4b039568197f683d0043d350b688dbe947c92b5cedcd7a64803791bd1a2dc6e0df0b9fb6a294d728e026dc9wb; + +unsigned g; + +_BitInt(6) +foo (unsigned a, unsigned b, unsigned c, unsigned _BitInt(256) z, + unsigned _BitInt(12419) y) +{ + y /= b; + unsigned _BitInt(12419) ay = a * y; + g -= (n >= ay ? n : ay) % c; + return z; +} +#endif + +int +main () +{ +#if __BITINT_MAXWIDTH__ >= 12419 + if (foo (0, 5, 5, 2, 0) != 2) + __builtin_abort (); +#endif +}
