https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84828
--- Comment #6 from Martin Liška <marxin at gcc dot gnu.org> --- I have a very similar issue: $ g++ /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pr84828.C /dev/null -mno-sse -Og /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pr84828.C: In function ‘void foo(float, double)’: /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pr84828.C:10:35: error: output constraint 0 must specify a single register asm volatile ("" : "+f" (c)); // { dg-error "must specify a single register" } ^ during RTL pass: stack /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pr84828.C:13:1: internal compiler error: in move_for_stack_reg, at reg-stack.c:1108 } ^ 0xd5f7ca move_for_stack_reg ../../gcc/reg-stack.c:1108 0xd60ead subst_stack_regs ../../gcc/reg-stack.c:2438 0xd610a0 convert_regs_1 ../../gcc/reg-stack.c:3072 0xd610a0 convert_regs_2 ../../gcc/reg-stack.c:3207 0xd627f8 convert_regs ../../gcc/reg-stack.c:3242 0xd627f8 reg_to_stack ../../gcc/reg-stack.c:3367 0xd627f8 rest_of_handle_stack_regs ../../gcc/reg-stack.c:3422 0xd627f8 execute ../../gcc/reg-stack.c:3453 Should I open another PR?