The code patched here is seeing whether the current function needs to save at least part of a register before using it.
2019-09-11 Richard Sandiford <richard.sandif...@arm.com> gcc/ * df-scan.c (df_get_entry_block_def_set): Use crtl->abi to test whether the current function needs to save at least part of a register before using it. (df_get_exit_block_use_set): Likewise for epilogue restores. Index: gcc/df-scan.c =================================================================== --- gcc/df-scan.c 2019-09-11 19:48:07.405959747 +0100 +++ gcc/df-scan.c 2019-09-11 19:48:11.009934354 +0100 @@ -3499,7 +3499,9 @@ df_get_entry_block_def_set (bitmap entry /* Defs for the callee saved registers are inserted so that the pushes have some defining location. */ for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) - if ((call_used_or_fixed_reg_p (i) == 0) && (df_regs_ever_live_p (i))) + if (!crtl->abi->clobbers_full_reg_p (i) + && !fixed_regs[i] + && df_regs_ever_live_p (i)) bitmap_set_bit (entry_block_defs, i); } @@ -3672,8 +3674,9 @@ df_get_exit_block_use_set (bitmap exit_b { /* Mark all call-saved registers that we actually used. */ for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) - if (df_regs_ever_live_p (i) && !LOCAL_REGNO (i) - && !TEST_HARD_REG_BIT (regs_invalidated_by_call, i)) + if (df_regs_ever_live_p (i) + && !LOCAL_REGNO (i) + && !crtl->abi->clobbers_full_reg_p (i)) bitmap_set_bit (exit_block_uses, i); }