From a743a72714fc4a9d7036d28d0cacdf2a3621f629 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Wed, 18 May 2022 13:00:47 -0700 Subject: [PATCH] DSE: Use the constant store source if possible RTL DSE tracks redundant constant stores within a basic block. When RTL loop invariant motion hoists a constant initialization out of the loop into a separate basic block, the constant store value becomes unknown within the original basic block. When recording store for RTL DSE, check if the source register is set only once to a constant by a non-partial unconditional load. If yes, record the constant as the constant store source. It eliminates unrolled zero stores after memset 0 in a loop where a vector register is used as the zero store source. gcc/ PR rtl-optimization/105638 * df-core.cc (df_find_single_def_src): Moved and renamed from find_single_def_src in loop-iv.cc. Change the argument to rtx and use rtx_equal_p. Return null for partial or conditional defs. * df.h (df_find_single_def_src): New prototype. * dse.cc (record_store): Use the constant source if the source register is set only once. * loop-iv.cc (find_single_def_src): Moved to df-core.cc. (replace_single_def_regs): Replace find_single_def_src with df_find_single_def_src. gcc/testsuite/ PR rtl-optimization/105638 * g++.target/i386/pr105638.C: New test. --- gcc/df-core.cc | 41 +++++++++++++++++++++ gcc/df.h | 1 + gcc/dse.cc | 8 +++++ gcc/loop-iv.cc | 45 +----------------------- gcc/testsuite/g++.target/i386/pr105638.C | 44 +++++++++++++++++++++++ 5 files changed, 95 insertions(+), 44 deletions(-) create mode 100644 gcc/testsuite/g++.target/i386/pr105638.C diff --git a/gcc/df-core.cc b/gcc/df-core.cc index a901b84878f7..e3a56bf6a9ff 100644 --- a/gcc/df-core.cc +++ b/gcc/df-core.cc @@ -2009,6 +2009,47 @@ df_reg_used (rtx_insn *insn, rtx reg) return df_find_use (insn, reg) != NULL; } +/* If REG has a single definition, return its known value, otherwise return + null. */ + +rtx +df_find_single_def_src (rtx reg) +{ + rtx src = NULL_RTX; + + /* Don't look through unbounded number of single definition REG copies, + there might be loops for sources with uninitialized variables. */ + for (int cnt = 0; cnt < 128; cnt++) + { + df_ref adef = DF_REG_DEF_CHAIN (REGNO (reg)); + if (adef == NULL || DF_REF_NEXT_REG (adef) != NULL + || DF_REF_IS_ARTIFICIAL (adef) + || (DF_REF_FLAGS (adef) + & (DF_REF_PARTIAL | DF_REF_CONDITIONAL))) + return NULL_RTX; + + rtx set = single_set (DF_REF_INSN (adef)); + if (set == NULL || !rtx_equal_p (SET_DEST (set), reg)) + return NULL_RTX; + + rtx note = find_reg_equal_equiv_note (DF_REF_INSN (adef)); + if (note && function_invariant_p (XEXP (note, 0))) + return XEXP (note, 0); + src = SET_SRC (set); + + if (REG_P (src)) + { + reg = src; + continue; + } + break; + } + if (!function_invariant_p (src)) + return NULL_RTX; + + return src; +} + /*---------------------------------------------------------------------------- Debugging and printing functions. diff --git a/gcc/df.h b/gcc/df.h index bd329205d08c..71e249ad20a5 100644 --- a/gcc/df.h +++ b/gcc/df.h @@ -991,6 +991,7 @@ extern df_ref df_find_def (rtx_insn *, rtx); extern bool df_reg_defined (rtx_insn *, rtx); extern df_ref df_find_use (rtx_insn *, rtx); extern bool df_reg_used (rtx_insn *, rtx); +extern rtx df_find_single_def_src (rtx); extern void df_worklist_dataflow (struct dataflow *,bitmap, int *, int); extern void df_print_regset (FILE *file, const_bitmap r); extern void df_print_word_regset (FILE *file, const_bitmap r); diff --git a/gcc/dse.cc b/gcc/dse.cc index 30c11cee0348..994c60dc1897 100644 --- a/gcc/dse.cc +++ b/gcc/dse.cc @@ -1508,6 +1508,14 @@ record_store (rtx body, bb_info_t bb_info) if (tem && CONSTANT_P (tem)) const_rhs = tem; + else + { + /* If RHS is set only once to a constant, set CONST_RHS + to the constant. */ + rtx def_src = df_find_single_def_src (rhs); + if (def_src != nullptr && CONSTANT_P (def_src)) + const_rhs = def_src; + } } } diff --git a/gcc/loop-iv.cc b/gcc/loop-iv.cc index 0eafe7d2362d..d639336445a4 100644 --- a/gcc/loop-iv.cc +++ b/gcc/loop-iv.cc @@ -1378,49 +1378,6 @@ simple_rhs_p (rtx rhs) } } -/* If REGNO has a single definition, return its known value, otherwise return - null. */ - -static rtx -find_single_def_src (unsigned int regno) -{ - rtx src = NULL_RTX; - - /* Don't look through unbounded number of single definition REG copies, - there might be loops for sources with uninitialized variables. */ - for (int cnt = 0; cnt < 128; cnt++) - { - df_ref adef = DF_REG_DEF_CHAIN (regno); - if (adef == NULL || DF_REF_NEXT_REG (adef) != NULL - || DF_REF_IS_ARTIFICIAL (adef)) - return NULL_RTX; - - rtx set = single_set (DF_REF_INSN (adef)); - if (set == NULL || !REG_P (SET_DEST (set)) - || REGNO (SET_DEST (set)) != regno) - return NULL_RTX; - - rtx note = find_reg_equal_equiv_note (DF_REF_INSN (adef)); - if (note && function_invariant_p (XEXP (note, 0))) - { - src = XEXP (note, 0); - break; - } - src = SET_SRC (set); - - if (REG_P (src)) - { - regno = REGNO (src); - continue; - } - break; - } - if (!function_invariant_p (src)) - return NULL_RTX; - - return src; -} - /* If any registers in *EXPR that have a single definition, try to replace them with the known-equivalent values. */ @@ -1433,7 +1390,7 @@ replace_single_def_regs (rtx *expr) { rtx x = *iter; if (REG_P (x)) - if (rtx new_x = find_single_def_src (REGNO (x))) + if (rtx new_x = df_find_single_def_src (x)) { *expr = simplify_replace_rtx (*expr, x, new_x); goto repeat; diff --git a/gcc/testsuite/g++.target/i386/pr105638.C b/gcc/testsuite/g++.target/i386/pr105638.C new file mode 100644 index 000000000000..ff40a459de14 --- /dev/null +++ b/gcc/testsuite/g++.target/i386/pr105638.C @@ -0,0 +1,44 @@ +/* { dg-do compile { target { ! ia32 } } } */ +/* { dg-options "-std=gnu++20 -O2 -march=skylake" } */ +/* { dg-final { scan-assembler-not "vpxor" } } */ + +#include +#include +#include + +class FastBoard { +public: + typedef std::pair movescore_t; + typedef std::tr1::array scoredlist_t; + +protected: + std::vector m_critical; + + int m_boardsize; +}; + +class FastState { +public: + FastBoard board; + + int movenum; +protected: + FastBoard::scoredlist_t scoredmoves; +}; + +class KoState : public FastState { +private: + std::vector ko_hash_history; + std::vector hash_history; +}; + +class GameState : public KoState { +public: + void foo (); +private: + std::vector game_history; +}; + +void GameState::foo() { + game_history.resize(movenum); +} -- 2.47.2