>>> if (rhs_uns) >>> return wi::ge_p (min, 0); // if min >= 0 then range contains positive >>> values >>> else >>> return wi::le_p (max, wi::max_value (TYPE_PRECISION (TREE_TYPE >>> (ssa)), SIGNED); // if max <= signed-max-of-type then range doesn't >>> need sign-extension >> >> I think we will have to check that ssa has necessary sign/zero extension >> when assigned to lhs_type. If PROMOTE_MODE tells us that ssa's type will >> be interpreted differently, the value range of ssa also will have >> corresponding range. In this cases, shouldn’t we have to check for >> upper and lower limit for both min and max? > > Hmm? That's exactly what the check is testing... we know that > min <= max thus if min >= 0 then max >= 0. > > zero_extension will never do anything on [0, INF] > > If max < MAX-SIGNED then sign-extension will not do anything. Ok, > sign-extension will do sth for negative values still. So rather > > if (rhs_uns) > return wi::geu_p (min, 0); > else > return wi::ges_p (min, 0) && wi::les_p (max, wi::max_value > (TYPE_PRECISION (TREE_TYPE (ssa)), SIGNED)); > > ?
Thanks for the explanation. I agree. Don’t we have to however check this on lhs_uns as this function is checking if ssa is promoted for lhs_sign and lhs_mode? Here is an attempt based on this. I ran regression testing with arm-none-linux-gnueabi on qemu-arm without any new regressions. Sine I am not comparing value ranges to see if it can be represented in lhs_sigh, I can now skip the PROMOTED_MODE check. I am still using wide_int::from (instead of wi::max_value) to get the limit as I have to match the precision with min, max precision. otherwise wide_int comparisons will not work. Is there a better way for this? /* Return TRUE if value in SSA is already zero/sign extended for lhs type (type here is the combination of LHS_MODE and LHS_UNS) using value range information stored. Return FALSE otherwise. */ bool promoted_for_type_p (tree ssa, enum machine_mode lhs_mode, bool lhs_uns) { wide_int min, max, limit; tree lhs_type; bool rhs_uns; signop rhs_signop; if (ssa == NULL_TREE || TREE_CODE (ssa) != SSA_NAME || !INTEGRAL_TYPE_P (TREE_TYPE (ssa))) return false; /* Return FALSE if value_range is not recorded for SSA. */ if (get_range_info (ssa, &min, &max) != VR_RANGE) return false; rhs_uns = TYPE_UNSIGNED (TREE_TYPE (ssa)); rhs_signop = rhs_uns ? UNSIGNED : SIGNED; lhs_type = lang_hooks.types.type_for_mode (lhs_mode, lhs_uns); limit = wide_int::from (TYPE_MAX_VALUE (lhs_type), TYPE_PRECISION (TREE_TYPE (ssa)), SIGNED); if (lhs_uns) /* If min >= 0 then range contains positive values and doesnt need zero-extension. */ return wi::ge_p (min, 0, rhs_signop); else /* If min >= 0 and max <= signed-max-of-type then range doesn't need sign-extension. */ return wi::ge_p (min, 0, rhs_signop) && wi::le_p (max, limit, rhs_signop); } Thanks, Kugan