https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52394
--- Comment #2 from Oleg Endo <olegendo at gcc dot gnu.org> --- The SH2A bitops seem to produce some of the insns, but it seems the generated code is either really bad (defeating the original purpose) or broken. For example: volatile struct { union { unsigned char BYTE; struct { unsigned char BIT7:1; unsigned char BIT6:1; unsigned char BIT5:1; unsigned char BIT4:1; unsigned char BIT3:1; unsigned char BIT2:1; unsigned char BIT1:1; unsigned char BIT0:1; } BIT; } ICR0; } USRSTR; int main (unsigned char a, unsigned char b, unsigned char c) { USRSTR.ICR0.BIT.BIT5 |= b & 1; return 0; } compiled with -m2a -mb -mbitops -O2: mov.l .L2,r2 // addr of USRSTR mov #1,r1 and r1,r5 // b & 1 mov #0,r0 bor.b #5,@(0,r2) // T |= (bit in mem) movt r7 // r7 = T mov.b @r2,r3 // load byte cmp/pl r7 // T = r7 mov #5,r7 movt r1 // r1 = T bclr #5,r3 // clear bit 5 of loaded byte shld r7,r1 // T << 5 or r3,r1 // OR bit mov.b r1,@r2 // write back rts/n It seems that this will produce funny results at the first bor.b insn because at function entry the T bit is undefined. The code should actually be something like this: mov.l .L2,r2 bld #0,r5 mov #0,r0 bor.b #5,@(0,r2) bst.b #5,@(0,r2)