Ping for the front-end maintainers' input. On Mon, 22 May 2023, Richard Biener wrote: > On Thu, May 18, 2023 at 11:04 PM Alexander Monakov via Gcc-patches > wrote: > > > > Implement -ffp-contract=on for C and C++ without changing default > > behavior (=off for -std=cNN, =fast for C++ and -std=gnuNN). > > The documentation changes mention the defaults are changed for > standard modes, I suppose you want to remove that hunk. > > > gcc/c-family/ChangeLog: > > > > * c-gimplify.cc (fma_supported_p): New helper. > > (c_gimplify_expr) [PLUS_EXPR, MINUS_EXPR]: Implement FMA > > contraction. > > > > gcc/ChangeLog: > > > > * common.opt (fp_contract_mode) [on]: Remove fallback. > > * config/sh/sh.md (*fmasf4): Correct flag_fp_contract_mode test. > > * doc/invoke.texi (-ffp-contract): Update. > > * trans-mem.cc (diagnose_tm_1): Skip internal function calls. > > --- > > gcc/c-family/c-gimplify.cc | 78 ++++++++++++++++++++++++++++++++++++++ > > gcc/common.opt | 3 +- > > gcc/config/sh/sh.md | 2 +- > > gcc/doc/invoke.texi | 8 ++-- > > gcc/trans-mem.cc | 3 ++ > > 5 files changed, 88 insertions(+), 6 deletions(-) > > > > diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc > > index ef5c7d919f..f7635d3b0c 100644 > > --- a/gcc/c-family/c-gimplify.cc > > +++ b/gcc/c-family/c-gimplify.cc > > @@ -41,6 +41,8 @@ along with GCC; see the file COPYING3. If not see > > #include "c-ubsan.h" > > #include "tree-nested.h" > > #include "context.h" > > +#include "tree-pass.h" > > +#include "internal-fn.h" > > > > /* The gimplification pass converts the language-dependent trees > > (ld-trees) emitted by the parser into language-independent trees > > @@ -686,6 +688,14 @@ c_build_bind_expr (location_t loc, tree block, tree body) > > return bind; > > } > > > > +/* Helper for c_gimplify_expr: test if target supports fma-like FN. */ > > + > > +static bool > > +fma_supported_p (enum internal_fn fn, tree type) > > +{ > > + return direct_internal_fn_supported_p (fn, type, OPTIMIZE_FOR_BOTH); > > +} > > + > > /* Gimplification of expression trees. */ > > > > /* Do C-specific gimplification on *EXPR_P. PRE_P and POST_P are as in > > @@ -739,6 +749,74 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED, > > break; > > } > > > > + case PLUS_EXPR: > > + case MINUS_EXPR: > > + { > > + tree type = TREE_TYPE (*expr_p); > > + /* For -ffp-contract=on we need to attempt FMA contraction only > > + during initial gimplification. Late contraction across statement > > + boundaries would violate language semantics. */ > > + if (SCALAR_FLOAT_TYPE_P (type) > > + && flag_fp_contract_mode == FP_CONTRACT_ON > > + && cfun && !(cfun->curr_properties & PROP_gimple_any) > > + && fma_supported_p (IFN_FMA, type)) > > + { > > + bool neg_mul = false, neg_add = code == MINUS_EXPR; > > + > > + tree *op0_p = &TREE_OPERAND (*expr_p, 0); > > + tree *op1_p = &TREE_OPERAND (*expr_p, 1); > > + > > + /* Look for ±(x * y) ± z, swapping operands if necessary. */ > > + if (TREE_CODE (*op0_p) == NEGATE_EXPR > > + && TREE_CODE (TREE_OPERAND (*op0_p, 0)) == MULT_EXPR) > > + /* '*EXPR_P' is '-(x * y) ± z'. This is fine. */; > > + else if (TREE_CODE (*op0_p) != MULT_EXPR) > > + { > > + std::swap (op0_p, op1_p); > > + std::swap (neg_mul, neg_add); > > + } > > + if (TREE_CODE (*op0_p) == NEGATE_EXPR) > > + { > > + op0_p = &TREE_OPERAND (*op0_p, 0); > > + neg_mul = !neg_mul; > > + } > > + if (TREE_CODE (*op0_p) != MULT_EXPR) > > + break; > > + auto_vec ops (3); > > + ops.quick_push (TREE_OPERAND (*op0_p, 0)); > > + ops.quick_push (TREE_OPERAND (*op0_p, 1)); > > + ops.quick_push (*op1_p); > > + > > + enum internal_fn ifn = IFN_FMA; > > + if (neg_mul) > > + { > > + if (fma_supported_p (IFN_FNMA, type)) > > + ifn = IFN_FNMA; > > + else > > + ops[0] = build1 (NEGATE_EXPR, type, ops[0]); > > + } > > + if (neg_add) > > + { > > + enum internal_fn ifn2 = ifn == IFN_FMA ? IFN_FMS : IFN_FNMS; > > + if (fma_supported_p (ifn2, type)) > > + ifn = ifn2; > > + else > > + ops[2] = build1 (NEGATE_EXPR, type, ops[2]); > > + } > > + for (auto &&op : ops) > > + if (gimplify_expr (&op, pre_p, post_p, is_gimple_val, fb_rvalue) > > + == GS_ERROR) > > + return GS_ERROR; > > + > > + gcall *call = gimple_build_call_internal_vec (ifn, ops); > > + gimple_seq_add_stmt_without_update (pre_p, call); > > + *expr_p = create_tmp_var (type); > > + gimple_call_set_lhs (call, *expr_p); > > it would be possible to do > > *expr_p = build_call_expr_internal (ifn, type, ops[0], ops[1]. ops[2]); > return GS_OK; > > and not worry about temporary creation and gimplifying of the operands. > That would in theory also leave the possibility to do this during > genericization instead (and avoid the guard against late invocation of > the hook). > > Otherwise it looks OK, but I'll let frontend maintainers have a chance to look > as well. > > Thanks for tackling this long-standing issue. > Richard. > > > + return GS_ALL_DONE; > > + } > > + break; > > + } > > + > > default:; > > } > > > > diff --git a/gcc/common.opt b/gcc/common.opt > > index a28ca13385..3daec85aef 100644 > > --- a/gcc/common.opt > > +++ b/gcc/common.opt > > @@ -1662,9 +1662,8 @@ Name(fp_contract_mode) Type(enum fp_contract_mode) UnknownError(unknown floating > > EnumValue > > Enum(fp_contract_mode) String(off) Value(FP_CONTRACT_OFF) > > > > -; Not implemented, fall back to conservative FP_CONTRACT_OFF. > > EnumValue > > -Enum(fp_contract_mode) String(on) Value(FP_CONTRACT_OFF) > > +Enum(fp_contract_mode) String(on) Value(FP_CONTRACT_ON) > > > > EnumValue > > Enum(fp_contract_mode) String(fast) Value(FP_CONTRACT_FAST) > > diff --git a/gcc/config/sh/sh.md b/gcc/config/sh/sh.md > > index 4622dba012..5cb1795482 100644 > > --- a/gcc/config/sh/sh.md > > +++ b/gcc/config/sh/sh.md > > @@ -9269,7 +9269,7 @@ (define_insn_and_split "*fmasf4" > > (match_operand:SF 3 "arith_reg_operand" "0"))) > > (clobber (reg:SI FPSCR_STAT_REG)) > > (use (reg:SI FPSCR_MODES_REG))] > > - "TARGET_SH2E && flag_fp_contract_mode != FP_CONTRACT_OFF" > > + "TARGET_SH2E && flag_fp_contract_mode == FP_CONTRACT_FAST" > > "fmac %1,%2,%0" > > "&& can_create_pseudo_p ()" > > [(parallel [(set (match_dup 0) > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > > index b92b857602..cb1e9a1d9f 100644 > > --- a/gcc/doc/invoke.texi > > +++ b/gcc/doc/invoke.texi > > @@ -11983,10 +11983,12 @@ This option is enabled by default at optimization levels @option{-O1}, > > such as forming of fused multiply-add operations if the target has > > native support for them. > > @option{-ffp-contract=on} enables floating-point expression contraction > > -if allowed by the language standard. This is currently not implemented > > -and treated equal to @option{-ffp-contract=off}. > > +if allowed by the language standard. This is implemented for C and C++, > > +where it enables contraction within one expression, but not across > > +different statements. > > > > -The default is @option{-ffp-contract=fast}. > > +The default is @option{-ffp-contract=off} for C in a standards compliant mode > > +(@option{-std=c11} or similar), @option{-ffp-contract=fast} otherwise. > > > > @opindex fomit-frame-pointer > > @item -fomit-frame-pointer > > diff --git a/gcc/trans-mem.cc b/gcc/trans-mem.cc > > index 4b129663e0..2174faef4c 100644 > > --- a/gcc/trans-mem.cc > > +++ b/gcc/trans-mem.cc > > @@ -637,6 +637,9 @@ diagnose_tm_1 (gimple_stmt_iterator *gsi, bool *handled_ops_p, > > { > > case GIMPLE_CALL: > > { > > + if (gimple_call_internal_p (stmt)) > > + break; > > + > > tree fn = gimple_call_fn (stmt); > > > > if ((d->summary_flags & DIAG_TM_OUTER) == 0 > > -- > > 2.39.2 > > >