https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78588
--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> --- Author: trippels Date: Wed Nov 30 07:30:55 2016 New Revision: 242997 URL: https://gcc.gnu.org/viewcvs?rev=242997&root=gcc&view=rev Log: Fix PR78588 - rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for 64-bit type Building gcc with -fsanitize=undefined shows: rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for 64-bit type 'long unsigned int' This happens because if_then_else_cond() in combine.c calls num_sign_bit_copies() in rtlanal.c with mode==BLKmode. 5205 bitwidth = GET_MODE_PRECISION (mode); 5206 if (bitwidth > HOST_BITS_PER_WIDE_INT) 5207 return 1; 5208 5209 nonzero = nonzero_bits (x, mode); 5210 return nonzero & (HOST_WIDE_INT_1U << (bitwidth - 1)) 5211 ? 1 : bitwidth - floor_log2 (nonzero) - 1; This causes (bitwidth - 1) to wrap around. PR rtl-optimization/78588 * combine.c (if_then_else_cond): Also guard against BLKmode. * rtlanal.c (num_sign_bit_copies1): Add assert. Modified: trunk/gcc/ChangeLog trunk/gcc/combine.c trunk/gcc/rtlanal.c
