From: Aldy Hernandez Date: Wed, 11 Nov 2020 19:10:42 +0000 (+0100) Subject: Refactor VRP threading code into vrp_jump_threader class. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=7cc52bc85e90ed71e67c443f14137f2fcf6adf3c;p=gcc.git Refactor VRP threading code into vrp_jump_threader class. gcc/ChangeLog: * tree-vrp.c (identify_jump_threads): Refactor to.. (vrp_jump_threader::vrp_jump_threader): ...here (vrp_jump_threader::~vrp_jump_threader): ...and here. (vrp_jump_threader::after_dom_children): Rename vr_values to m_vr_values. (execute_vrp): Use vrp_jump_threader. --- diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c index d3816ab569e..6b77c357a8f 100644 --- a/gcc/tree-vrp.c +++ b/gcc/tree-vrp.c @@ -4152,32 +4152,87 @@ vrp_prop::finalize () } } +/* Blocks which have more than one predecessor and more than + one successor present jump threading opportunities, i.e., + when the block is reached from a specific predecessor, we + may be able to determine which of the outgoing edges will + be traversed. When this optimization applies, we are able + to avoid conditionals at runtime and we may expose secondary + optimization opportunities. + + This class is effectively a driver for the generic jump + threading code. It basically just presents the generic code + with edges that may be suitable for jump threading. + + Unlike DOM, we do not iterate VRP if jump threading was successful. + While iterating may expose new opportunities for VRP, it is expected + those opportunities would be very limited and the compile time cost + to expose those opportunities would be significant. + + As jump threading opportunities are discovered, they are registered + for later realization. */ + class vrp_jump_threader : public dom_walker { public: - vrp_jump_threader (cdi_direction direction, - class const_and_copies *const_and_copies, - class avail_exprs_stack *avail_exprs_stack) - : dom_walker (direction, REACHABLE_BLOCKS), - m_const_and_copies (const_and_copies), - m_avail_exprs_stack (avail_exprs_stack), - m_dummy_cond (NULL) {} - - virtual edge before_dom_children (basic_block); - virtual void after_dom_children (basic_block); + vrp_jump_threader (struct function *, vr_values *); + ~vrp_jump_threader (); - class vr_values *vr_values; + void thread_jumps () + { + walk (m_fun->cfg->x_entry_block_ptr); + } private: static tree simplify_stmt (gimple *stmt, gimple *within_stmt, avail_exprs_stack *, basic_block); + virtual edge before_dom_children (basic_block); + virtual void after_dom_children (basic_block); - class const_and_copies *m_const_and_copies; - class avail_exprs_stack *m_avail_exprs_stack; - + function *m_fun; + vr_values *m_vr_values; + const_and_copies *m_const_and_copies; + avail_exprs_stack *m_avail_exprs_stack; + hash_table *m_avail_exprs; gcond *m_dummy_cond; }; +vrp_jump_threader::vrp_jump_threader (struct function *fun, vr_values *v) + : dom_walker (CDI_DOMINATORS, REACHABLE_BLOCKS) +{ + /* Ugh. When substituting values earlier in this pass we can wipe + the dominance information. So rebuild the dominator information + as we need it within the jump threading code. */ + calculate_dominance_info (CDI_DOMINATORS); + + /* We do not allow VRP information to be used for jump threading + across a back edge in the CFG. Otherwise it becomes too + difficult to avoid eliminating loop exit tests. Of course + EDGE_DFS_BACK is not accurate at this time so we have to + recompute it. */ + mark_dfs_back_edges (); + + /* Allocate our unwinder stack to unwind any temporary equivalences + that might be recorded. */ + m_const_and_copies = new const_and_copies (); + + m_dummy_cond = NULL; + m_fun = fun; + m_vr_values = v; + m_avail_exprs = new hash_table (1024); + m_avail_exprs_stack = new avail_exprs_stack (m_avail_exprs); +} + +vrp_jump_threader::~vrp_jump_threader () +{ + /* We do not actually update the CFG or SSA graphs at this point as + ASSERT_EXPRs are still in the IL and cfg cleanup code does not + yet handle ASSERT_EXPRs gracefully. */ + delete m_const_and_copies; + delete m_avail_exprs; + delete m_avail_exprs_stack; +} + /* Called before processing dominator children of BB. We want to look at ASSERT_EXPRs and record information from them in the appropriate tables. @@ -4295,7 +4350,7 @@ vrp_jump_threader::after_dom_children (basic_block bb) integer_zero_node, integer_zero_node, NULL, NULL); - x_vr_values = vr_values; + x_vr_values = m_vr_values; thread_outgoing_edges (bb, m_dummy_cond, m_const_and_copies, m_avail_exprs_stack, NULL, simplify_stmt); @@ -4305,62 +4360,6 @@ vrp_jump_threader::after_dom_children (basic_block bb) m_const_and_copies->pop_to_marker (); } -/* Blocks which have more than one predecessor and more than - one successor present jump threading opportunities, i.e., - when the block is reached from a specific predecessor, we - may be able to determine which of the outgoing edges will - be traversed. When this optimization applies, we are able - to avoid conditionals at runtime and we may expose secondary - optimization opportunities. - - This routine is effectively a driver for the generic jump - threading code. It basically just presents the generic code - with edges that may be suitable for jump threading. - - Unlike DOM, we do not iterate VRP if jump threading was successful. - While iterating may expose new opportunities for VRP, it is expected - those opportunities would be very limited and the compile time cost - to expose those opportunities would be significant. - - As jump threading opportunities are discovered, they are registered - for later realization. */ - -static void -identify_jump_threads (struct function *fun, class vr_values *vr_values) -{ - /* Ugh. When substituting values earlier in this pass we can - wipe the dominance information. So rebuild the dominator - information as we need it within the jump threading code. */ - calculate_dominance_info (CDI_DOMINATORS); - - /* We do not allow VRP information to be used for jump threading - across a back edge in the CFG. Otherwise it becomes too - difficult to avoid eliminating loop exit tests. Of course - EDGE_DFS_BACK is not accurate at this time so we have to - recompute it. */ - mark_dfs_back_edges (); - - /* Allocate our unwinder stack to unwind any temporary equivalences - that might be recorded. */ - const_and_copies *equiv_stack = new const_and_copies (); - - hash_table *avail_exprs - = new hash_table (1024); - avail_exprs_stack *avail_exprs_stack - = new class avail_exprs_stack (avail_exprs); - - vrp_jump_threader walker (CDI_DOMINATORS, equiv_stack, avail_exprs_stack); - walker.vr_values = vr_values; - walker.walk (fun->cfg->x_entry_block_ptr); - - /* We do not actually update the CFG or SSA graphs at this point as - ASSERT_EXPRs are still in the IL and cfg cleanup code does not yet - handle ASSERT_EXPRs gracefully. */ - delete equiv_stack; - delete avail_exprs; - delete avail_exprs_stack; -} - /* STMT is a conditional at the end of a basic block. If the conditional is of the form SSA_NAME op constant and the SSA_NAME @@ -4516,7 +4515,8 @@ execute_vrp (struct function *fun, bool warn_array_bounds_p) /* We must identify jump threading opportunities before we release the datastructures built by VRP. */ - identify_jump_threads (fun, &vrp_prop.vr_values); + vrp_jump_threader threader (fun, &vrp_prop.vr_values); + threader.thread_jumps (); /* A comparison of an SSA_NAME against a constant where the SSA_NAME was set by a type conversion can often be rewritten to use the