Hi! On Fri, Dec 14, 2018 at 09:21:26AM +0000, senthilkumar.selva...@microchip.com wrote: > This patch fixes PR 88253 by preventing combine_simplify_rtx from > folding an rtx with side_effects_p to const0_rtx.
> 2018-12-14 Senthil Kumar Selvaraj <senthilkumar.selva...@microchip.com> > > PR 88253.c > * combine.c (combine_simplify_rtx): Test for side-effects before > substituting by zero. > > gcc/testsuite/ChangeLog: > > 2018-12-14 Senthil Kumar Selvaraj <senthilkumar.selva...@microchip.com> > > * gcc.target/avr/pr88253.c: New test. > diff --git gcc/combine.c gcc/combine.c > index 7e611399f2c..e634e8f5a7e 100644 > --- gcc/combine.c > +++ gcc/combine.c > @@ -5978,6 +5978,7 @@ combine_simplify_rtx (rtx x, machine_mode op0_mode, int > in_dest, > && known_eq (subreg_lowpart_offset (int_mode, int_op0_mode), > SUBREG_BYTE (x)) > && HWI_COMPUTABLE_MODE_P (int_op0_mode) > + && !side_effects_p (SUBREG_REG (x)) > && (nonzero_bits (SUBREG_REG (x), int_op0_mode) > & GET_MODE_MASK (int_mode)) == 0) > return CONST0_RTX (int_mode); Please move the !side_effects_p test last (it is expensive). With that, okay for trunk and backports to 8 and 7. Thanks! Segher
