https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96536
Bug ID: 96536 Summary: -fcf-protection code in i386.md:restore_stack_nonlocal uses invalid compare-and-jump rtl Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: rsandifo at gcc dot gnu.org Target Milestone: --- Target: x86_64 Noticed while working on an optimisation that the -fcf-protection code in restore_stack_nonlocal uses a branch based on a clobber result: (insn 14 13 15 2 (parallel [ (set (reg:DI 85) (minus:DI (reg:DI 85) (mem:DI (plus:DI (reg/f:DI 82) (const_int 16 [0x10])) [2 S8 A8]))) (clobber (reg:CC 17 flags)) ]) "gcc/testsuite/gcc.target/i386/cet-sjlj-1.c":16:3 -1 (nil)) (jump_insn 15 14 40 2 (set (pc) (if_then_else (eq (reg:CCZ 17 flags) (const_int 0 [0])) (label_ref 28) (pc))) "gcc/testsuite/gcc.target/i386/cet-sjlj-1.c":16:3 -1 (int_list:REG_BR_PROB 536870916 (nil)) -> 28) IMO this is invalid RTL. A clobber: Represents the storing or possible storing of an unpredictable, undescribed value … but this usage requires it to be predictable. I think we need to use the parallel-SET *sub<mode>_2 representation instead.