Thanks Richard. Address comments on V3: https://gcc.gnu.org/pipermail/gcc-patches/2023-September/630699.html
juzhe.zh...@rivai.ai From: Richard Sandiford Date: 2023-09-17 23:29 To: Juzhe-Zhong CC: gcc-patches; rguenther Subject: Re: [PATCH V2] internal-fn: Support undefined rtx for uninitialized SSA_NAME Juzhe-Zhong <juzhe.zh...@rivai.ai> writes: > According to PR: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751 > > As Richard and Richi suggested, we recognize uninitialized SSA_NAME and > convert it > into SCRATCH rtx if the target predicate allows SCRATCH. > > It can help to reduce redundant data move instructions of targets like RISC-V. > > gcc/ChangeLog: > > * internal-fn.cc (expand_fn_using_insn): Support undefined rtx. > * optabs.cc (maybe_legitimize_operand): Ditto. > (can_reuse_operands_p): Ditto. > * optabs.h (enum expand_operand_type): Ditto. > (create_undefined_input_operand): Ditto. > > --- > gcc/internal-fn.cc | 4 ++++ > gcc/optabs.cc | 16 ++++++++++++++++ > gcc/optabs.h | 14 +++++++++++++- > 3 files changed, 33 insertions(+), 1 deletion(-) > > diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc > index 0fd34359247..61d5a9e4772 100644 > --- a/gcc/internal-fn.cc > +++ b/gcc/internal-fn.cc > @@ -247,6 +247,10 @@ expand_fn_using_insn (gcall *stmt, insn_code icode, > unsigned int noutputs, > create_convert_operand_from (&ops[opno], rhs_rtx, > TYPE_MODE (rhs_type), > TYPE_UNSIGNED (rhs_type)); > + else if (TREE_CODE (rhs) == SSA_NAME > + && SSA_NAME_IS_DEFAULT_DEF (rhs) > + && VAR_P (SSA_NAME_VAR (rhs))) > + create_undefined_input_operand (&ops[opno], TYPE_MODE (rhs_type)); > else > create_input_operand (&ops[opno], rhs_rtx, TYPE_MODE (rhs_type)); > opno += 1; > diff --git a/gcc/optabs.cc b/gcc/optabs.cc > index 32ff379ffc3..d8c771547a3 100644 > --- a/gcc/optabs.cc > +++ b/gcc/optabs.cc > @@ -8102,6 +8102,21 @@ maybe_legitimize_operand (enum insn_code icode, > unsigned int opno, > goto input; > } > break; > + > + case EXPAND_UNDEFINED: > + { > + mode = insn_data[(int) icode].operand[opno].mode; > + rtx scratch = gen_rtx_SCRATCH (mode); A scratch of the right mode should already be available in op->value, since it was created by create_undefined_input_operand. If that doesn't work for some reason, then it would be better for create_undefined_input_operand to pass NULL_RTX as the "value" argument to create_expand_operand. > + /* For SCRATCH rtx which is converted from uninitialized > + SSA, we convert it as fresh pseudo when target doesn't > + allow scratch rtx in predicate. Otherwise, return true. */ > + if (!insn_operand_matches (icode, opno, scratch)) > + { > + op->value = gen_reg_rtx (mode); The mode should come from op->mode. > + goto input; > + } > + return true; > + } > } > return insn_operand_matches (icode, opno, op->value); > } > @@ -8147,6 +8162,7 @@ can_reuse_operands_p (enum insn_code icode, > case EXPAND_INPUT: > case EXPAND_ADDRESS: > case EXPAND_INTEGER: > + case EXPAND_UNDEFINED: > return true; I think this should be in the "return false" block instead. > > case EXPAND_CONVERT_TO: > diff --git a/gcc/optabs.h b/gcc/optabs.h > index c80b7f4dc1b..4eb1f9ee09a 100644 > --- a/gcc/optabs.h > +++ b/gcc/optabs.h > @@ -37,7 +37,8 @@ enum expand_operand_type { > EXPAND_CONVERT_TO, > EXPAND_CONVERT_FROM, > EXPAND_ADDRESS, > - EXPAND_INTEGER > + EXPAND_INTEGER, > + EXPAND_UNDEFINED Sorry, this was my bad suggestion. I should have suggested EXPAND_UNDEFINED_INPUT, to match the name of the function. Thanks, Richard > }; > > /* Information about an operand for instruction expansion. */ > @@ -117,6 +118,17 @@ create_input_operand (class expand_operand *op, rtx > value, > create_expand_operand (op, EXPAND_INPUT, value, mode, false); > } > > +/* Make OP describe an undefined input operand for uninitialized > + SSA. It's the scratch operand with mode MODE; MODE cannot be > + VOIDmode. */ > + > +inline void > +create_undefined_input_operand (class expand_operand *op, machine_mode mode) > +{ > + create_expand_operand (op, EXPAND_UNDEFINED, gen_rtx_SCRATCH (mode), mode, > + false); > +} > + > /* Like create_input_operand, except that VALUE must first be converted > to mode MODE. UNSIGNED_P says whether VALUE is unsigned. */
