https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123822
--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <[email protected]>: https://gcc.gnu.org/g:794acc6340cb2869a74fc69104c38ac5c2840a91 commit r16-8064-g794acc6340cb2869a74fc69104c38ac5c2840a91 Author: Andrew Pinski <[email protected]> Date: Wed Mar 11 13:01:08 2026 -0700 simplify-rtx: Fix the case where subreg of a vec_concat could fail [PR123822] So combine (rightfully) produces: (subreg:DD (vec_concat:V2DI (const_int -1 [0xffffffffffffffff]) (reg:DI 145 [ _22 ])) 0) And then calls simplify_subreg on it. simplify_subreg then sees it can remove the vec_concat as this is the lower part and try to do `(subreg:DD (const_int -1 [0xffffffffffffffff]))` but that is an invalid constant for DF64 so simplify_subreg rejects that and returns NULL but there is code in simplify_subreg to create a SUBREG then if the subreg validates. The problem is we are using DImode for the inner mode and that validates but when gen_rtx_SUBREG is called the inner mode of DImode is not there; only VOIDmode. So the fix is to check for VOIDmode before the call to validate_subreg. Bootstrapped and tested on x86_64-linux-gnu. And lightly tested for aarch64-linux-gnu. PR rtl-optimization/123822 gcc/ChangeLog: * simplify-rtx.cc (simplify_context::simplify_subreg): Check the mode of the part to be non-VOIDmode before calling gen_rtx_SUBREG. gcc/testsuite/ChangeLog: * gcc.dg/torture/pr123822-1.c: New test. Signed-off-by: Andrew Pinski <[email protected]>
