#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "tm_p.h"
#include "basic-block.h"
#include "gimple-pretty-print.h"
#include "gimple.h"
#include "gimple-ssa.h"
#include "tree-phinodes.h"
#include "ssa-iterators.h"
#include "tree-ssanames.h"
#include "tree-pass.h"
#include "langhooks.h"
#include "flags.h"

Include dependency graph for tree-ssa-phiprop.c:

Data Structures
struct	phiprop_d

Functions
static bool	phivn_valid_p ()
static tree	phiprop_insert_phi (basic_block bb, gimple phi, gimple use_stmt, struct phiprop_d *phivn, size_t n)
static bool	propagate_with_phi (basic_block bb, gimple phi, struct phiprop_d *phivn, size_t n)
static unsigned int	tree_ssa_phiprop ()
static bool	gate_phiprop ()
gimple_opt_pass *	make_pass_phiprop ()

Function Documentation

static bool gate_phiprop ( )

static

gimple_opt_pass* make_pass_phiprop ( )

static tree phiprop_insert_phi	(	basic_block	bb,
		gimple	phi,
		gimple	use_stmt,
		struct phiprop_d *	phivn,
		size_t	n
	)

static

Insert a new phi node for the dereference of PHI at basic_block BB with the virtual operands from USE_STMT.

 Build a new PHI node to replace the definition of
 the indirect reference lhs.

 Add PHI arguments for each edge inserting loads of the
 addressable operands.

         Reuse a formerly created dereference.

static bool phivn_valid_p ( )

static

Verify if the value recorded for NAME in PHIVN is still valid at the start of basic block BB.

The def stmts of the virtual uses need to be dominated by bb.

     If BB does not dominate a VDEF, the value is invalid.

Referenced by propagate_with_phi().

static bool propagate_with_phi	(	basic_block	bb,
		gimple	phi,
		struct phiprop_d *	phivn,
		size_t	n
	)

static

Propagate between the phi node arguments of PHI in BB and phi result users. For now this matches

p_2 = PHI <&x, &y>

<Lx>:; p_3 = p_2; z_2 = *p_3; and converts it to

z_2 = PHI <x, y>

<Lx>:; Returns true if a transformation was done and edge insertions need to be committed. Global data PHIVN and N is used to track past transformation results. We need to be especially careful here with aliasing issues as we are moving memory reads.

 Check if we can "cheaply" dereference all phi arguments.

     Walk the ssa chain until we reach a ssa name we already
     created a value for or we reach a definition of the form
     ssa_name_n = &var;

 Find a dereferencing use.  First follow (single use) ssa
 copy chains for ptr.

 Replace the first dereference of *ptr if there is one and if we
 can move the loads to the place of the ptr phi node.

     Check whether this is a load of *ptr.

           We cannot replace a load that may throw or is volatile.

     Check if we can move the loads.  The def stmt of the virtual use
     needs to be in a different basic block dominating bb.

     Found a proper dereference.  Insert a phi node if this
     is the first load transformation.

         Remember the value we created for *ptr.

         Remove old stmt.  The phi is taken care of by DCE, if we
         want to delete it here we also have to delete all intermediate
         copies.

         Further replacements are easy, just make a copy out of the
         load.

     Continue searching for a proper dereference.

References gimple_assign_rhs1(), gimple_assign_single_p(), NULL_TREE, phivn_valid_p(), SSA_NAME_DEF_STMT, SSA_NAME_IS_DEFAULT_DEF, SSA_NAME_VERSION, TREE_CODE, TREE_TYPE, types_compatible_p(), and USE_FROM_PTR.

static unsigned int tree_ssa_phiprop ( )

static

Main entry for phiprop pass.

Walk the dominator tree in preorder.

Data Structures

Functions

Function Documentation

p_2 = PHI <&x, &y>

z_2 = PHI <x, y>