On Sun, Sep 25, 2022 at 9:56 PM Tamar Christina wrote: > > > -----Original Message----- > > From: Andrew Pinski > > Sent: Saturday, September 24, 2022 8:57 PM > > To: Tamar Christina > > Cc: gcc-patches@gcc.gnu.org; nd ; rguenther@suse.de > > Subject: Re: [PATCH 1/2]middle-end Fold BIT_FIELD_REF and Shifts into > > BIT_FIELD_REFs alone > > > > On Fri, Sep 23, 2022 at 4:43 AM Tamar Christina via Gcc-patches > patches@gcc.gnu.org> wrote: > > > > > > Hi All, > > > > > > This adds a match.pd rule that can fold right shifts and > > > bit_field_refs of integers into just a bit_field_ref by adjusting the > > > offset and the size of the extract and adds an extend to the previous size. > > > > > > Concretely turns: > > > > > > #include > > > > > > unsigned int foor (uint32x4_t x) > > > { > > > return x[1] >> 16; > > > } > > > > > > which used to generate: > > > > > > _1 = BIT_FIELD_REF ; > > > _3 = _1 >> 16; > > > > > > into > > > > > > _4 = BIT_FIELD_REF ; > > > _2 = (unsigned int) _4; > > > > > > I currently limit the rewrite to only doing it if the resulting > > > extract is in a mode the target supports. i.e. it won't rewrite it to > > > extract say 13-bits because I worry that for targets that won't have a > > > bitfield extract instruction this may be a de-optimization. > > > > It is only a de-optimization for the following case: > > * vector extraction > > > > All other cases should be handled correctly in the middle-end when > > expanding to RTL because they need to be handled for bit-fields anyways. > > Plus SIGN_EXTRACT and ZERO_EXTRACT would be used in the integer case > > for the RTL. > > Getting SIGN_EXTRACT/ZERO_EXTRACT early on in the RTL is better than > > waiting until combine really. > > > > Fair enough, I've dropped the constraint. Well the constraint should be done still for VECTOR_TYPE I think. Attached is what I had done for left shift for integer types. Note the BYTES_BIG_ENDIAN part which you missed for the right shift case. Thanks, Andrew Pinski > > > > > > > > > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu > > > and no issues. > > > > > > Testcase are added in patch 2/2. > > > > > > Ok for master? > > > > > > Thanks, > > > Tamar > > > > > > gcc/ChangeLog: > > > > > > * match.pd: Add bitfield and shift folding. > > > > > > --- inline copy of patch -- > > > diff --git a/gcc/match.pd b/gcc/match.pd index > > > > > 1d407414bee278c64c00d425d9f025c1c58d853d..b225d36dc758f1581502c8d03 > > 761 > > > 544bfd499c01 100644 > > > --- a/gcc/match.pd > > > +++ b/gcc/match.pd > > > @@ -7245,6 +7245,23 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > > && ANY_INTEGRAL_TYPE_P (type) && ANY_INTEGRAL_TYPE_P > > (TREE_TYPE(@0))) > > > (IFN_REDUC_PLUS_WIDEN @0))) > > > > > > +/* Canonicalize BIT_FIELD_REFS and shifts to BIT_FIELD_REFS. */ (for > > > +shift (rshift) > > > + op (plus) > > > + (simplify > > > + (shift (BIT_FIELD_REF @0 @1 @2) integer_pow2p@3) > > > + (if (INTEGRAL_TYPE_P (type)) > > > + (with { /* Can't use wide-int here as the precision differs between > > > + @1 and @3. */ > > > + unsigned HOST_WIDE_INT size = tree_to_uhwi (@1); > > > + unsigned HOST_WIDE_INT shiftc = tree_to_uhwi (@3); > > > + unsigned HOST_WIDE_INT newsize = size - shiftc; > > > + tree nsize = wide_int_to_tree (bitsizetype, newsize); > > > + tree ntype > > > + = build_nonstandard_integer_type (newsize, 1); } > > > > Maybe use `build_nonstandard_integer_type (newsize, /* unsignedp = */ > > true);` or better yet `build_nonstandard_integer_type (newsize, > > UNSIGNED);` > > Ah, will do, > Tamar. > > > > > I had started to convert some of the unsignedp into enum signop but I never > > finished or submitted the patch. > > > > Thanks, > > Andrew Pinski > > > > > > > + (if (ntype) > > > + (convert:type (BIT_FIELD_REF:ntype @0 { nsize; } (op @2 > > > + @3)))))))) > > > + > > > (simplify > > > (BIT_FIELD_REF (BIT_FIELD_REF @0 @1 @2) @3 @4) > > > (BIT_FIELD_REF @0 @3 { const_binop (PLUS_EXPR, bitsizetype, @2, @4); > > > })) > > > > > > > > > > > > > > > --