On Tue, Jul 2, 2024 at 3:43 PM Georg-Johann Lay <a...@gjlay.de> wrote: > > Hi Jeff, > > This is a patch to get correct code out of 64-bit > loads from address-space __memx. > > The AVR address-spaces may require that move insns issue > calls to library support functions, a fact that -ftree-ter > doesn't account for. tree-ssa-ter.cc then replaces an > expression across such a library call, resulting in wrong code. > > This patch disables that pass per default on avr, as there is no > more fine grained way to avoid malicious optimizations. > The pass can still be re-enabled by means of explicit -ftree-ter. > > Ok to apply?
I think this requires more details on what goes wrong - I assume it's not stmt reordering that effectively happens but recursive expand_expr on SSA defs when those invoke libcalls? In that case this would point to a deeper issue. So - if the wrongness is already apparent in the RTL expansion pass dump can you quote the respective pieces and explain why? > As an alternative, the option could be disabled permanently in > avr.cc::avr_option_override(). > > Johann > > -- > > AVR: middle-end/87376 - Use -fno-tree-ter per default. > > Temporary expression replacement might replace expressions across > library calls, for example with move insn from address-space __memx > like in PR87376. -ftree-ter has no way where the backend could hook > in to avoid only problematic replacements, thus kick it out altogether. > > PR middle-end/87376 > gcc/ > * common/config/avr/avr-common.cc (avr_option_optimization_table) > <OPT_ftree_ter>: Set to 0. > gcc/testsuite/ > * gcc.target/avr/torture/pr87376-memx.c: New test.
