From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id 0F49D3858D1E for ; Wed, 17 May 2023 13:02:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 0F49D3858D1E Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1684328546; x=1715864546; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=Wpcchos+ojkMr0xMRs1ze6aeaDChXlBkVLuq6vnADO4=; b=ZV3Q7iYQ1rlCWGqecVv8+XIxw0sGtBn2kVCp5oc6azk8E/TDQLz/yYdl OvaTEppuJHPIwd6Y3jvirTL0XaekclOi5x8ysukrV6czqpHeDRKSj0FLi ydByDKHTKusgXbZ+xsaSTizUYy6GZtv283pM6pSDrTis737AfTlQfc9XA 4hS76lVglocKz8tFL0a0mYf25HCLgZzZw78dvjDfYK9mTIbtKILEBo5s4 rmWQMgMbg+YcAfcQmJyqnj6kaMjqfHfOGwjiA6zvEJHBygVCSYFgluYtE oxRdsX05OzknBAHMzS1fWhU2K2wLs3C2N8adVcrBhn9/SRHpmEqpI6YTk g==; X-IronPort-AV: E=McAfee;i="6600,9927,10713"; a="332111848" X-IronPort-AV: E=Sophos;i="5.99,282,1677571200"; d="scan'208";a="332111848" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2023 06:02:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10713"; a="732417794" X-IronPort-AV: E=Sophos;i="5.99,282,1677571200"; d="scan'208";a="732417794" Received: from scymds03.sc.intel.com ([10.148.94.166]) by orsmga008.jf.intel.com with ESMTP; 17 May 2023 06:02:24 -0700 Received: from shgcc101.sh.intel.com (shgcc101.sh.intel.com [10.239.85.97]) by scymds03.sc.intel.com (Postfix) with ESMTP id 28B6B7B; Wed, 17 May 2023 06:02:22 -0700 (PDT) From: "Cui, Lili" To: gcc-patches@gcc.gnu.org Cc: richard.guenther@gmail.com, Lili Cui Subject: [PATCH] PR gcc/98350:Handle FMA friendly in reassoc pass Date: Wed, 17 May 2023 13:02:22 +0000 Message-Id: <20230517130222.2534562-1-lili.cui@intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.0 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: From: Lili Cui Make some changes in reassoc pass to make it more friendly to fma pass later. Using FMA instead of mult + add reduces register pressure and insruction retired. There are mainly two changes 1. Put no-mult ops and mult ops alternately at the end of the queue, which is conducive to generating more fma and reducing the loss of FMA when breaking the chain. 2. Rewrite the rewrite_expr_tree_parallel function to try to build parallel chains according to the given correlation width, keeping the FMA chance as much as possible. TEST1: float foo (float a, float b, float c, float d, float *e) { return *e + a * b + c * d ; } For "-Ofast -mfpmath=sse -mfma" GCC generates: vmulss %xmm3, %xmm2, %xmm2 vfmadd132ss %xmm1, %xmm2, %xmm0 vaddss (%rdi), %xmm0, %xmm0 ret With this patch GCC generates: vfmadd213ss (%rdi), %xmm1, %xmm0 vfmadd231ss %xmm2, %xmm3, %xmm0 ret TEST2: for (int i = 0; i < N; i++) { a[i] += b[i]* c[i] + d[i] * e[i] + f[i] * g[i] + h[i] * j[i] + k[i] * l[i] + m[i]* o[i] + p[i]; } For "-Ofast -mfpmath=sse -mfma" GCC generates: vmovapd e(%rax), %ymm4 vmulpd d(%rax), %ymm4, %ymm3 addq $32, %rax vmovapd c-32(%rax), %ymm5 vmovapd j-32(%rax), %ymm6 vmulpd h-32(%rax), %ymm6, %ymm2 vmovapd a-32(%rax), %ymm6 vaddpd p-32(%rax), %ymm6, %ymm0 vmovapd g-32(%rax), %ymm7 vfmadd231pd b-32(%rax), %ymm5, %ymm3 vmovapd o-32(%rax), %ymm4 vmulpd m-32(%rax), %ymm4, %ymm1 vmovapd l-32(%rax), %ymm5 vfmadd231pd f-32(%rax), %ymm7, %ymm2 vfmadd231pd k-32(%rax), %ymm5, %ymm1 vaddpd %ymm3, %ymm0, %ymm0 vaddpd %ymm2, %ymm0, %ymm0 vaddpd %ymm1, %ymm0, %ymm0 vmovapd %ymm0, a-32(%rax) cmpq $8192, %rax jne .L4 vzeroupper ret with this patch applied GCC breaks the chain with width = 2 and generates 6 fma: vmovapd a(%rax), %ymm2 vmovapd c(%rax), %ymm0 addq $32, %rax vmovapd e-32(%rax), %ymm1 vmovapd p-32(%rax), %ymm5 vmovapd g-32(%rax), %ymm3 vmovapd j-32(%rax), %ymm6 vmovapd l-32(%rax), %ymm4 vmovapd o-32(%rax), %ymm7 vfmadd132pd b-32(%rax), %ymm2, %ymm0 vfmadd132pd d-32(%rax), %ymm5, %ymm1 vfmadd231pd f-32(%rax), %ymm3, %ymm0 vfmadd231pd h-32(%rax), %ymm6, %ymm1 vfmadd231pd k-32(%rax), %ymm4, %ymm0 vfmadd231pd m-32(%rax), %ymm7, %ymm1 vaddpd %ymm1, %ymm0, %ymm0 vmovapd %ymm0, a-32(%rax) cmpq $8192, %rax jne .L2 vzeroupper ret gcc/ChangeLog: PR gcc/98350 * tree-ssa-reassoc.cc (rewrite_expr_tree_parallel): Rewrite this function. (rank_ops_for_fma): New. (reassociate_bb): Handle new function. gcc/testsuite/ChangeLog: PR gcc/98350 * gcc.dg/pr98350-1.c: New test. * gcc.dg/pr98350-2.c: Ditto. --- gcc/testsuite/gcc.dg/pr98350-1.c | 31 ++++ gcc/testsuite/gcc.dg/pr98350-2.c | 11 ++ gcc/tree-ssa-reassoc.cc | 256 +++++++++++++++++++++---------- 3 files changed, 215 insertions(+), 83 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr98350-1.c create mode 100644 gcc/testsuite/gcc.dg/pr98350-2.c diff --git a/gcc/testsuite/gcc.dg/pr98350-1.c b/gcc/testsuite/gcc.dg/pr98350-1.c new file mode 100644 index 00000000000..185511c5e0a --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr98350-1.c @@ -0,0 +1,31 @@ +/* { dg-do compile } */ +/* { dg-options "-Ofast -mfpmath=sse -mfma -Wno-attributes " } */ + +/* Test that the compiler properly optimizes multiply and add + to generate more FMA instructions. */ +#define N 1024 +double a[N]; +double b[N]; +double c[N]; +double d[N]; +double e[N]; +double f[N]; +double g[N]; +double h[N]; +double j[N]; +double k[N]; +double l[N]; +double m[N]; +double o[N]; +double p[N]; + + +void +foo (void) +{ + for (int i = 0; i < N; i++) + { + a[i] += b[i] * c[i] + d[i] * e[i] + f[i] * g[i] + h[i] * j[i] + k[i] * l[i] + m[i]* o[i] + p[i]; + } +} +/* { dg-final { scan-assembler-times "vfm" 6 } } */ diff --git a/gcc/testsuite/gcc.dg/pr98350-2.c b/gcc/testsuite/gcc.dg/pr98350-2.c new file mode 100644 index 00000000000..b35d88aead9 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr98350-2.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-Ofast -mfpmath=sse -mfma -Wno-attributes " } */ + +/* Test that the compiler rearrange the ops to generate more FMA. */ + +float +foo1 (float a, float b, float c, float d, float *e) +{ + return *e + a * b + c * d ; +} +/* { dg-final { scan-assembler-times "vfm" 2 } } */ diff --git a/gcc/tree-ssa-reassoc.cc b/gcc/tree-ssa-reassoc.cc index 067a3f07f7e..52c8aab6033 100644 --- a/gcc/tree-ssa-reassoc.cc +++ b/gcc/tree-ssa-reassoc.cc @@ -54,6 +54,7 @@ along with GCC; see the file COPYING3. If not see #include "tree-ssa-reassoc.h" #include "tree-ssa-math-opts.h" #include "gimple-range.h" +#include "internal-fn.h" /* This is a simple global reassociation pass. It is, in part, based on the LLVM pass of the same name (They do some things more/less @@ -5468,14 +5469,24 @@ get_reassociation_width (int ops_num, enum tree_code opc, return width; } -/* Recursively rewrite our linearized statements so that the operators - match those in OPS[OPINDEX], putting the computation in rank - order and trying to allow operations to be executed in - parallel. */ +/* Rewrite statements with dependency chain with regard to the chance to + generate FMA. + For the chain with FMA: Try to keep fma opportunity as much as possible. + For the chain without FMA: Putting the computation in rank order and trying + to allow operations to be executed in parallel. + E.g. + e + f + g + a * b + c * d; + ssa1 = e + f; + ssa2 = g + a * b; + ssa3 = ssa1 + c * d; + ssa4 = ssa2 + ssa3; + + This reassociation approach preserves the chance of fma generation as much + as possible. */ static void -rewrite_expr_tree_parallel (gassign *stmt, int width, - const vec &ops) +rewrite_expr_tree_parallel (gassign *stmt, int width, bool has_fma, + const vec &ops) { enum tree_code opcode = gimple_assign_rhs_code (stmt); int op_num = ops.length (); @@ -5483,10 +5494,11 @@ rewrite_expr_tree_parallel (gassign *stmt, int width, int stmt_num = op_num - 1; gimple **stmts = XALLOCAVEC (gimple *, stmt_num); int op_index = op_num - 1; - int stmt_index = 0; - int ready_stmts_end = 0; - int i = 0; - gimple *stmt1 = NULL, *stmt2 = NULL; + int width_count = width; + int i = 0, j = 0; + tree tmp_op[2], op1; + operand_entry *oe; + gimple *stmt1 = NULL; tree last_rhs1 = gimple_assign_rhs1 (stmt); /* We start expression rewriting from the top statements. @@ -5496,91 +5508,84 @@ rewrite_expr_tree_parallel (gassign *stmt, int width, for (i = stmt_num - 2; i >= 0; i--) stmts[i] = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (stmts[i+1])); - for (i = 0; i < stmt_num; i++) + /* Build parallel dependency chain according to width. */ + for (i = 0; i < width; i++) { - tree op1, op2; - - /* Determine whether we should use results of - already handled statements or not. */ - if (ready_stmts_end == 0 - && (i - stmt_index >= width || op_index < 1)) - ready_stmts_end = i; - - /* Now we choose operands for the next statement. Non zero - value in ready_stmts_end means here that we should use - the result of already generated statements as new operand. */ - if (ready_stmts_end > 0) - { - op1 = gimple_assign_lhs (stmts[stmt_index++]); - if (ready_stmts_end > stmt_index) - op2 = gimple_assign_lhs (stmts[stmt_index++]); - else if (op_index >= 0) - { - operand_entry *oe = ops[op_index--]; - stmt2 = oe->stmt_to_insert; - op2 = oe->op; - } - else - { - gcc_assert (stmt_index < i); - op2 = gimple_assign_lhs (stmts[stmt_index++]); - } + /* */ + if (op_index > 1 && !has_fma) + swap_ops_for_binary_stmt (ops, op_index - 2); - if (stmt_index >= ready_stmts_end) - ready_stmts_end = 0; - } - else + for (j = 0; j < 2; j++) { - if (op_index > 1) - swap_ops_for_binary_stmt (ops, op_index - 2); - operand_entry *oe2 = ops[op_index--]; - operand_entry *oe1 = ops[op_index--]; - op2 = oe2->op; - stmt2 = oe2->stmt_to_insert; - op1 = oe1->op; - stmt1 = oe1->stmt_to_insert; + gcc_assert (op_index >= 0); + oe = ops[op_index--]; + tmp_op[j] = oe->op; + /* If the stmt that defines operand has to be inserted, insert it + before the use. */ + stmt1 = oe->stmt_to_insert; + if (stmt1) + insert_stmt_before_use (stmts[i], stmt1); + stmt1 = NULL; } - - /* If we emit the last statement then we should put - operands into the last statement. It will also - break the loop. */ - if (op_index < 0 && stmt_index == i) - i = stmt_num - 1; + stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1), tmp_op[1], tmp_op[0], opcode); + gimple_set_visited (stmts[i], true); if (dump_file && (dump_flags & TDF_DETAILS)) { - fprintf (dump_file, "Transforming "); + fprintf (dump_file, " into "); print_gimple_stmt (dump_file, stmts[i], 0); } + } - /* If the stmt that defines operand has to be inserted, insert it - before the use. */ - if (stmt1) - insert_stmt_before_use (stmts[i], stmt1); - if (stmt2) - insert_stmt_before_use (stmts[i], stmt2); - stmt1 = stmt2 = NULL; - - /* We keep original statement only for the last one. All - others are recreated. */ - if (i == stmt_num - 1) + for (i = width; i < stmt_num; i++) + { + /* We keep original statement only for the last one. All others are + recreated. */ + if ( op_index < 0) { - gimple_assign_set_rhs1 (stmts[i], op1); - gimple_assign_set_rhs2 (stmts[i], op2); - update_stmt (stmts[i]); + if (width_count == 2) + { + + /* We keep original statement only for the last one. All + others are recreated. */ + gimple_assign_set_rhs1 (stmts[i], gimple_assign_lhs (stmts[i-1])); + gimple_assign_set_rhs2 (stmts[i], gimple_assign_lhs (stmts[i-2])); + update_stmt (stmts[i]); + } + else + { + + stmts[i] = + build_and_add_sum (TREE_TYPE (last_rhs1), + gimple_assign_lhs (stmts[i-width_count]), + gimple_assign_lhs (stmts[i-width_count+1]), + opcode); + gimple_set_visited (stmts[i], true); + width_count--; + } } else { - stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1), op1, op2, opcode); + /* Attach the rest of the ops to the parallel dependency chain. */ + oe = ops[op_index--]; + op1 = oe->op; + stmt1 = oe->stmt_to_insert; + if (stmt1) + insert_stmt_before_use (stmts[i], stmt1); + stmt1 = NULL; + stmts[i] = build_and_add_sum (TREE_TYPE (last_rhs1), + gimple_assign_lhs (stmts[i-width]), + op1, + opcode); gimple_set_visited (stmts[i], true); } + if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " into "); print_gimple_stmt (dump_file, stmts[i], 0); } } - remove_visited_stmt_chain (last_rhs1); } @@ -6649,6 +6654,76 @@ transform_stmt_to_multiply (gimple_stmt_iterator *gsi, gimple *stmt, } } +/* Rearrange ops to generate more FMA when the chain may has more than 2 fmas. + Put no-mult ops and mult ops alternately at the end of the queue, which is + conducive to generating more fma and reducing the loss of FMA when breaking + the chain. + E.g. + a * b + c * d + e generates: + + _4 = c_9(D) * d_10(D); + _12 = .FMA (a_7(D), b_8(D), _4); + _11 = e_6(D) + _12; + + Rtearrange ops to -> e + a * b + c * d generates: + + _4 = .FMA (c_7(D), d_8(D), _3); + _11 = .FMA (a_5(D), b_6(D), _4); + */ +static bool +rank_ops_for_fma (vec *ops) +{ + operand_entry *oe; + unsigned int i; + unsigned int ops_length = ops->length (); + auto_vec ops_mult; + auto_vec ops_others; + + FOR_EACH_VEC_ELT (*ops, i, oe) + { + if (TREE_CODE (oe->op) == SSA_NAME) + { + gimple *def_stmt = SSA_NAME_DEF_STMT (oe->op); + if (is_gimple_assign (def_stmt) + && gimple_assign_rhs_code (def_stmt) == MULT_EXPR) + ops_mult.safe_push (oe); + else + ops_others.safe_push (oe); + } + else + ops_others.safe_push (oe); + } + /* When ops_mult.length == 2, like the following case, + + a * b + c * d + e. + + we need to rearrange the ops. + + Putting ops that not def from mult in front can generate more fmas. */ + if (ops_mult.length () >= 2) + { + /* If all ops are defined with mult, we don't need to rearrange them. */ + if (ops_mult.length () != ops_length) + { + /* Put no-mult ops and mult ops alternately at the end of the + queue, which is conducive to generating more fma and reducing the + loss of FMA when breaking the chain. */ + ops->truncate (0); + ops->splice (ops_mult); + int j, opindex = ops->length (); + int others_length = ops_others.length(); + for (j = 0; j < others_length; j++) + { + oe = ops_others.pop (); + ops->safe_insert (opindex, oe); + if (opindex > 0) + opindex--; + } + } + return true; + } + return false; +} /* Reassociate expressions in basic block BB and its post-dominator as children. @@ -6813,6 +6888,7 @@ reassociate_bb (basic_block bb) machine_mode mode = TYPE_MODE (TREE_TYPE (lhs)); int ops_num = ops.length (); int width; + bool has_fma = false; /* For binary bit operations, if there are at least 3 operands and the last operand in OPS is a constant, @@ -6821,11 +6897,23 @@ reassociate_bb (basic_block bb) often match a canonical bit test when we get to RTL. */ if (ops.length () > 2 && (rhs_code == BIT_AND_EXPR - || rhs_code == BIT_IOR_EXPR - || rhs_code == BIT_XOR_EXPR) + || rhs_code == BIT_IOR_EXPR + || rhs_code == BIT_XOR_EXPR) && TREE_CODE (ops.last ()->op) == INTEGER_CST) std::swap (*ops[0], *ops[ops_num - 1]); + optimization_type opt_type = bb_optimization_type (bb); + + /* If the target support FMA, rank_ops_for_fma will detect if + the chain has fmas and rearrange the ops if so. */ + if (direct_internal_fn_supported_p (IFN_FMA, + TREE_TYPE (lhs), + opt_type) + && (rhs_code == PLUS_EXPR || rhs_code == MINUS_EXPR)) + { + has_fma = rank_ops_for_fma(&ops); + } + /* Only rewrite the expression tree to parallel in the last reassoc pass to avoid useless work back-and-forth with initial linearization. */ @@ -6839,22 +6927,24 @@ reassociate_bb (basic_block bb) "Width = %d was chosen for reassociation\n", width); rewrite_expr_tree_parallel (as_a (stmt), - width, ops); + width, + has_fma, + ops); } else - { - /* When there are three operands left, we want - to make sure the ones that get the double - binary op are chosen wisely. */ - int len = ops.length (); - if (len >= 3) + { + /* When there are three operands left, we want + to make sure the ones that get the double + binary op are chosen wisely. */ + int len = ops.length (); + if (len >= 3 && !has_fma) swap_ops_for_binary_stmt (ops, len - 3); new_lhs = rewrite_expr_tree (stmt, rhs_code, 0, ops, powi_result != NULL || negate_result, len != orig_len); - } + } /* If we combined some repeated factors into a __builtin_powi call, multiply that result by the -- 2.25.1