https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116170
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Kewen Lin <li...@gcc.gnu.org>: https://gcc.gnu.org/g:49d5e21d41aed827038f6766140e2449a64a9726 commit r15-2899-g49d5e21d41aed827038f6766140e2449a64a9726 Author: Kewen Lin <li...@linux.ibm.com> Date: Tue Aug 13 04:28:28 2024 -0500 LRA: Don't emit move for substituted CONSTATNT_P operand [PR116170] Commit r15-2084 exposes one ICE in LRA. Firstly, before r15-2084 KFmode has 126 bit precision while V1TImode has 128 bit precision, so the subreg (subreg:V1TI (reg:KF 131) 0) is paradoxical_subreg_p, which stops some passes from doing some optimization. After r15-2084, KFmode has the same mode precision as V1TImode, passes are able to optimize more, but it causes this ICE in LRA as described below: For insn 106 (set (mem:V1TI ...) (subreg:V1TI (reg:KF 133) 0)), which matches pattern (define_insn "*vsx_le_perm_store_<mode>" [(set (match_operand:VSX_LE_128 0 "memory_operand" "=Z,Q") (match_operand:VSX_LE_128 1 "vsx_register_operand" "+wa,r"))] "!BYTES_BIG_ENDIAN && TARGET_VSX && !TARGET_P9_VECTOR && !altivec_indexed_or_indirect_operand (operands[0], <MODE>mode)" "@ # #" [(set_attr "type" "vecstore,store") (set_attr "length" "12,8") (set_attr "isa" "<VSisa>,*")]) LRA makes equivalence substitution on r133 with const double (const_double:KF 0.0), selects alternative 0 and fixes up operand 1 for constraint "wa", because operand 1 is OP_INOUT, so it considers assigning back to it as well, that is: lra_emit_move (type == OP_INOUT ? copy_rtx (old) : old, new_reg); But because old has been changed to const_double in equivalence substitution, the move is actually assigning to const_double, which is invalid and cause ICE. Considering reg:KF 133 is equivalent with (const_double:KF 0.0) even though this operand is OP_INOUT, IMHO there should not be any following uses of reg:KF 133, otherwise it doesn't have the chance to be equivalent to (const_double:KF 0.0). So this patch is to guard the lra_emit_move with !CONSTANT_P to exclude such case. PR rtl-optimization/116170 gcc/ChangeLog: * lra-constraints.cc (curr_insn_transform): Don't emit move back to old operand if it's CONSTANT_P. gcc/testsuite/ChangeLog: * gcc.target/powerpc/pr116170.c: New test.
