https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105394
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- We are calling tree_vec_extract with bitsize 32 but a QImode boolean type. ICK. (gdb) p debug_gimple_stmt (stmt) _8 = VEC_COND_EXPR <_6, _7, { 3.0e+0, 3.0e+0, 3.0e+0, 3.0e+0 }>; $15 = void (gdb) p debug_tree (a) <ssa_name 0x7ffff6492318 type <vector_type 0x7ffff66309d8 type <boolean_type 0x7ffff6630930 public QI size <integer_cst 0x7ffff6526348 constant 8> unit-size <integer_cst 0x7ffff6526360 constant 1> align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type 0x7ffff6630930 precision:4 min <integer_cst 0x7ffff662e300 -8> max <integer_cst 0x7ffff662e348 7>> V4BI size <integer_cst 0x7ffff6526408 constant 16> unit-size <integer_cst 0x7ffff6526420 constant 2> align:16 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type 0x7ffff66309d8 nunits:4> visited def_stmt _6 = _27; version:6> so we have a non 1-precision BImode bool. That's something we assume doesn't happen (here). I see V4BImode is 2 bytes in size, are there really 4 bits used for each element? The patch below assumes that and generates _40 = VIEW_CONVERT_EXPR<unsigned short>(_6); _41 = _40 & 15; _42 = _41 != 0 ? _30 : 3.0e+0; _43 = _40 & 240; _44 = _43 != 0 ? _33 : 3.0e+0; _45 = _40 & 3840; _46 = _45 != 0 ? _36 : 3.0e+0; _47 = _40 & 61440; _48 = _47 != 0 ? _39 : 3.0e+0; _8 = {_42, _44, _46, _48}; for the unsupported VEC_COND_EXPR. The approach won't work for variable-length vectors since we cannot pun that to an integer type (precision is always constant). So eventually using an adjusted BIT_FIELD_REF for the vector BImode case is better - as said the current code simply assumes a classical mask. I suppose for SVE we never run into unsupported conds?