diff options
Diffstat (limited to 'gcc/tree-ssa-phiopt.c')
| -rw-r--r-- | gcc/tree-ssa-phiopt.c | 315 |
1 files changed, 154 insertions, 161 deletions
diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c index 1ee39a5..9b5b563 100644 --- a/gcc/tree-ssa-phiopt.c +++ b/gcc/tree-ssa-phiopt.c @@ -59,7 +59,6 @@ along with GCC; see the file COPYING3. If not see #define HAVE_conditional_move (0) #endif -static unsigned int tree_ssa_phiopt (void); static unsigned int tree_ssa_phiopt_worker (bool, bool); static bool conditional_replacement (basic_block, basic_block, edge, edge, gimple, tree, tree); @@ -80,162 +79,6 @@ static void hoist_adjacent_loads (basic_block, basic_block, basic_block, basic_block); static bool gate_hoist_loads (void); -/* This pass tries to replaces an if-then-else block with an - assignment. We have four kinds of transformations. Some of these - transformations are also performed by the ifcvt RTL optimizer. - - Conditional Replacement - ----------------------- - - This transformation, implemented in conditional_replacement, - replaces - - bb0: - if (cond) goto bb2; else goto bb1; - bb1: - bb2: - x = PHI <0 (bb1), 1 (bb0), ...>; - - with - - bb0: - x' = cond; - goto bb2; - bb2: - x = PHI <x' (bb0), ...>; - - We remove bb1 as it becomes unreachable. This occurs often due to - gimplification of conditionals. - - Value Replacement - ----------------- - - This transformation, implemented in value_replacement, replaces - - bb0: - if (a != b) goto bb2; else goto bb1; - bb1: - bb2: - x = PHI <a (bb1), b (bb0), ...>; - - with - - bb0: - bb2: - x = PHI <b (bb0), ...>; - - This opportunity can sometimes occur as a result of other - optimizations. - - - Another case caught by value replacement looks like this: - - bb0: - t1 = a == CONST; - t2 = b > c; - t3 = t1 & t2; - if (t3 != 0) goto bb1; else goto bb2; - bb1: - bb2: - x = PHI (CONST, a) - - Gets replaced with: - bb0: - bb2: - t1 = a == CONST; - t2 = b > c; - t3 = t1 & t2; - x = a; - - ABS Replacement - --------------- - - This transformation, implemented in abs_replacement, replaces - - bb0: - if (a >= 0) goto bb2; else goto bb1; - bb1: - x = -a; - bb2: - x = PHI <x (bb1), a (bb0), ...>; - - with - - bb0: - x' = ABS_EXPR< a >; - bb2: - x = PHI <x' (bb0), ...>; - - MIN/MAX Replacement - ------------------- - - This transformation, minmax_replacement replaces - - bb0: - if (a <= b) goto bb2; else goto bb1; - bb1: - bb2: - x = PHI <b (bb1), a (bb0), ...>; - - with - - bb0: - x' = MIN_EXPR (a, b) - bb2: - x = PHI <x' (bb0), ...>; - - A similar transformation is done for MAX_EXPR. - - - This pass also performs a fifth transformation of a slightly different - flavor. - - Adjacent Load Hoisting - ---------------------- - - This transformation replaces - - bb0: - if (...) goto bb2; else goto bb1; - bb1: - x1 = (<expr>).field1; - goto bb3; - bb2: - x2 = (<expr>).field2; - bb3: - # x = PHI <x1, x2>; - - with - - bb0: - x1 = (<expr>).field1; - x2 = (<expr>).field2; - if (...) goto bb2; else goto bb1; - bb1: - goto bb3; - bb2: - bb3: - # x = PHI <x1, x2>; - - The purpose of this transformation is to enable generation of conditional - move instructions such as Intel CMOVE or PowerPC ISEL. Because one of - the loads is speculative, the transformation is restricted to very - specific cases to avoid introducing a page fault. We are looking for - the common idiom: - - if (...) - x = y->left; - else - x = y->right; - - where left and right are typically adjacent pointers in a tree structure. */ - -static unsigned int -tree_ssa_phiopt (void) -{ - return tree_ssa_phiopt_worker (false, gate_hoist_loads ()); -} - /* This pass tries to transform conditional stores into unconditional ones, enabling further simplifications with the simpler then and else blocks. In particular it replaces this: @@ -2200,8 +2043,155 @@ gate_hoist_loads (void) && HAVE_conditional_move); } -/* Always do these optimizations if we have SSA - trees to work on. */ +/* This pass tries to replaces an if-then-else block with an + assignment. We have four kinds of transformations. Some of these + transformations are also performed by the ifcvt RTL optimizer. + + Conditional Replacement + ----------------------- + + This transformation, implemented in conditional_replacement, + replaces + + bb0: + if (cond) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <0 (bb1), 1 (bb0), ...>; + + with + + bb0: + x' = cond; + goto bb2; + bb2: + x = PHI <x' (bb0), ...>; + + We remove bb1 as it becomes unreachable. This occurs often due to + gimplification of conditionals. + + Value Replacement + ----------------- + + This transformation, implemented in value_replacement, replaces + + bb0: + if (a != b) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <a (bb1), b (bb0), ...>; + + with + + bb0: + bb2: + x = PHI <b (bb0), ...>; + + This opportunity can sometimes occur as a result of other + optimizations. + + + Another case caught by value replacement looks like this: + + bb0: + t1 = a == CONST; + t2 = b > c; + t3 = t1 & t2; + if (t3 != 0) goto bb1; else goto bb2; + bb1: + bb2: + x = PHI (CONST, a) + + Gets replaced with: + bb0: + bb2: + t1 = a == CONST; + t2 = b > c; + t3 = t1 & t2; + x = a; + + ABS Replacement + --------------- + + This transformation, implemented in abs_replacement, replaces + + bb0: + if (a >= 0) goto bb2; else goto bb1; + bb1: + x = -a; + bb2: + x = PHI <x (bb1), a (bb0), ...>; + + with + + bb0: + x' = ABS_EXPR< a >; + bb2: + x = PHI <x' (bb0), ...>; + + MIN/MAX Replacement + ------------------- + + This transformation, minmax_replacement replaces + + bb0: + if (a <= b) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <b (bb1), a (bb0), ...>; + + with + + bb0: + x' = MIN_EXPR (a, b) + bb2: + x = PHI <x' (bb0), ...>; + + A similar transformation is done for MAX_EXPR. + + + This pass also performs a fifth transformation of a slightly different + flavor. + + Adjacent Load Hoisting + ---------------------- + + This transformation replaces + + bb0: + if (...) goto bb2; else goto bb1; + bb1: + x1 = (<expr>).field1; + goto bb3; + bb2: + x2 = (<expr>).field2; + bb3: + # x = PHI <x1, x2>; + + with + + bb0: + x1 = (<expr>).field1; + x2 = (<expr>).field2; + if (...) goto bb2; else goto bb1; + bb1: + goto bb3; + bb2: + bb3: + # x = PHI <x1, x2>; + + The purpose of this transformation is to enable generation of conditional + move instructions such as Intel CMOVE or PowerPC ISEL. Because one of + the loads is speculative, the transformation is restricted to very + specific cases to avoid introducing a page fault. We are looking for + the common idiom: + + if (...) + x = y->left; + else + x = y->right; + + where left and right are typically adjacent pointers in a tree structure. */ namespace { @@ -2229,7 +2219,10 @@ public: /* opt_pass methods: */ opt_pass * clone () { return new pass_phiopt (m_ctxt); } - unsigned int execute () { return tree_ssa_phiopt (); } + virtual unsigned int execute (function *) + { + return tree_ssa_phiopt_worker (false, gate_hoist_loads ()); + } }; // class pass_phiopt @@ -2267,7 +2260,7 @@ public: /* opt_pass methods: */ virtual bool gate (function *) { return flag_tree_cselim; } - unsigned int execute () { return tree_ssa_cs_elim (); } + virtual unsigned int execute (function *) { return tree_ssa_cs_elim (); } }; // class pass_cselim |