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tree-ssa-phiopt.c (abs_replacement): New function.

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* tree-ssa-phiopt.c (abs_replacement): New function.
        (empty_block_p): New function extracted from...
        (candidate_bb_for_phi_optimization): Break out empty block test.
        (conditional_replacement): Use empty_block_p.
        (value_replacement): Similarly.

        * gcc.dg/tree-ssa/20040514-2.c: Update expected output.
        * gcc.dg/tree-ssa/20040518-2.c: New test.

Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r82017
This commit is contained in:
Andrew Pinski 2004-05-19 03:35:19 +00:00 committed by Jeff Law
parent eeab4d81a6
commit cc52902d97
5 changed files with 237 additions and 22 deletions
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6
gcc/ChangeLog
View File

@ -40,6 +40,12 @@
2004-05-18 Andrew Pinski <pinskia@physics.uc.edu>
Jeff Law <law@redhat.com>
* tree-ssa-phiopt.c (abs_replacement): New function.
(empty_block_p): New function extracted from...
(candidate_bb_for_phi_optimization): Break out empty block test.
(conditional_replacement): Use empty_block_p.
(value_replacement): Similarly.
* Makefile.in (tree-ssa-phiopt.o): Depends on flags.h.
* tree-ssa-phiopt.c: Include flags.h.
(conditional_replacement): Remove argument names from prototype.

4
gcc/testsuite/ChangeLog
View File

@ -3,6 +3,10 @@
* gfortran.fortran-torture/execute/power.f90: Test constant integers.
2004-05-18 Andrew Pinski <pinskia@physics.uc.edu>
Jeff Law <law@redhat.com>
* gcc.dg/tree-ssa/20040514-2.c: Update expected output.
* gcc.dg/tree-ssa/20040518-2.c: New test.
* gcc.dg/tree-ssa/20040518-1.c: New test.

6
gcc/testsuite/gcc.dg/tree-ssa/20040514-2.c
View File

@ -11,5 +11,7 @@ foo2 (distance, i, j)
return t;
}
/* There should be no ABS_EXPR. */
/* { dg-final { scan-tree-dump-times "ABS_EXPR " 0 "dom3"} } */
/* There should be one ABS_EXPR and no conditionals. */
/* { dg-final { scan-tree-dump-times "ABS_EXPR " 1 "dom3"} } */
/* { dg-final { scan-tree-dump-times "if " 0 "dom3"} } */

16
gcc/testsuite/gcc.dg/tree-ssa/20040518-2.c Normal file
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@ -0,0 +1,16 @@
/* { dg-do compile } */
/* { dg-options "-O1 -fdump-tree-phiopt1-details" } */
int t( int i)
{
int j;
if(i>=0)
j = i;
else
j = -i;
return j;
}
/* We should convert one COND_EXPRs into straightline code with ABS. */
/* { dg-final { scan-tree-dump-times "straightline" 1 "phiopt1"} } */
/* { dg-final { scan-tree-dump-times "ABS_EXPR" 1 "phiopt1"} } */

227
gcc/tree-ssa-phiopt.c
View File

@ -39,11 +39,13 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
static void tree_ssa_phiopt (void);
static bool conditional_replacement (basic_block, tree, tree, tree);
static bool value_replacement (basic_block, tree, tree, tree);
static bool abs_replacement (basic_block, tree, tree, tree);
static void replace_phi_with_stmt (block_stmt_iterator, basic_block,
basic_block, tree, tree);
static bool candidate_bb_for_phi_optimization (basic_block,
basic_block *,
basic_block *);
static bool empty_block_p (basic_block);
/* This pass eliminates PHI nodes which can be trivially implemented as
an assignment from a conditional expression. ie if we have something
@ -82,8 +84,29 @@ static bool candidate_bb_for_phi_optimization (basic_block,
x = b;
This can sometimes occur as a result of other optimizations. A
similar transformation is done by the ifcvt RTL optimizer. */
similar transformation is done by the ifcvt RTL optimizer.
This pass also eliminates PHI nodes which are really absolute
values. i.e. if we have something like:
bb0:
if (a >= 0) goto bb2; else goto bb1;
bb1:
x = -a;
bb2:
x = PHI (x (bb1), a (bb0));
We can rewrite that as:
bb0:
bb1:
bb2:
x = ABS_EXPR< a >;
bb1 will become unreachable and bb0 and bb2 will almost always be merged
into a single block. Similar transformations are done by the ifcvt
RTL optimizer. */
static void
tree_ssa_phiopt (void)
{
@ -106,7 +129,8 @@ tree_ssa_phiopt (void)
/* Do the replacement of conditional if it can be done. */
if (conditional_replacement (bb, phi, arg0, arg1)
|| value_replacement (bb, phi, arg0, arg1))
|| value_replacement (bb, phi, arg0, arg1)
|| abs_replacement (bb, phi, arg0, arg1))
{
/* We have done the replacement so we need to rebuild the
cfg when this pass is complete. */
@ -121,12 +145,32 @@ tree_ssa_phiopt (void)
cleanup_tree_cfg ();
}
/* Return TRUE if block BB has no executable statements, otherwise return
FALSE. */
static bool
empty_block_p (basic_block bb)
{
block_stmt_iterator bsi;
/* BB must have no executable statements. */
bsi = bsi_start (bb);
while (!bsi_end_p (bsi)
&& (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR
|| IS_EMPTY_STMT (bsi_stmt (bsi))))
bsi_next (&bsi);
if (!bsi_end_p (bsi))
return false;
return true;
}
/* BB is a basic block which has only one PHI node with precisely two
arguments.
Examine both of BB's predecessors to see if one ends with a
COND_EXPR and the other is an empty block. If so, then we may
be able to optimize PHI nodes at the start of BB.
COND_EXPR and the other is a successor of the COND_EXPR. If so, then
we may be able to optimize PHI nodes at the start of BB.
If so, mark store the block with the COND_EXPR into COND_BLOCK_P
and the other block into OTHER_BLOCK_P and return true, otherwise
@ -138,12 +182,10 @@ candidate_bb_for_phi_optimization (basic_block bb,
basic_block *other_block_p)
{
tree last0, last1;
block_stmt_iterator bsi;
basic_block cond_block, other_block;
/* One of the alternatives must come from a block ending with
a COND_EXPR. The other block must be entirely empty, except
for labels. */
a COND_EXPR. */
last0 = last_stmt (bb->pred->src);
last1 = last_stmt (bb->pred->pred_next->src);
if (last0 && TREE_CODE (last0) == COND_EXPR)
@ -180,16 +222,6 @@ candidate_bb_for_phi_optimization (basic_block bb,
|| phi_nodes (other_block))
return false;
/* OTHER_BLOCK must have no executable statements. */
bsi = bsi_start (other_block);
while (!bsi_end_p (bsi)
&& (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR
|| IS_EMPTY_STMT (bsi_stmt (bsi))))
bsi_next (&bsi);
if (!bsi_end_p (bsi))
return false;
*cond_block_p = cond_block;
*other_block_p = other_block;
/* Everything looks OK. */
@ -271,7 +303,8 @@ conditional_replacement (basic_block bb, tree phi, tree arg0, tree arg1)
else
return false;
if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block))
if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block)
|| !empty_block_p (other_block))
return false;
/* If the condition is not a naked SSA_NAME and its type does not
@ -397,7 +430,8 @@ value_replacement (basic_block bb, tree phi, tree arg0, tree arg1)
if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
return false;
if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block))
if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block)
|| !empty_block_p (other_block))
return false;
cond = COND_EXPR_COND (last_stmt (cond_block));
@ -447,6 +481,159 @@ value_replacement (basic_block bb, tree phi, tree arg0, tree arg1)
return false;
}
/* The function absolute_replacement does the main work of doing the absolute
replacement. Return true if the replacement is done. Otherwise return
false.
bb is the basic block where the replacement is going to be done on. arg0
is argument 0 from the phi. Likewise for arg1. */
static bool
abs_replacement (basic_block bb, tree phi, tree arg0, tree arg1)
{
tree result;
basic_block other_block = NULL;
basic_block cond_block = NULL;
tree new, cond;
block_stmt_iterator bsi;
edge true_edge, false_edge;
tree assign = NULL;
edge e;
tree rhs = NULL, lhs = NULL;
bool negate;
enum tree_code cond_code;
/* If the type says honor signed zeros we cannot do this
optimization. */
if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
return false;
if (!candidate_bb_for_phi_optimization (bb, &cond_block, &other_block))
return false;
/* OTHER_BLOCK must have only one executable statement which must have the
form arg0 = -arg1 or arg1 = -arg0. */
bsi = bsi_start (other_block);
while (!bsi_end_p (bsi))
{
tree stmt = bsi_stmt (bsi);
/* Empty statements and labels are uninteresting. */
if (TREE_CODE (stmt) == LABEL_EXPR
|| IS_EMPTY_STMT (stmt))
{
bsi_next (&bsi);
continue;
}
/* If we found the assignment, but it was not the only executable
statement in OTHER_BLOCK, then we can not optimize. */
if (assign)
return false;
/* If we got here, then we have found the first executable statement
in OTHER_BLOCK. If it is anything other than arg = -arg1 or
arg1 = -arg0, then we can not optimize. */
if (TREE_CODE (stmt) == MODIFY_EXPR)
{
lhs = TREE_OPERAND (stmt, 0);
rhs = TREE_OPERAND (stmt, 1);
if (TREE_CODE (rhs) == NEGATE_EXPR)
{
rhs = TREE_OPERAND (rhs, 0);
/* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
if ((lhs == arg0 && rhs == arg1)
|| (lhs == arg1 && rhs == arg0))
{
assign = stmt;
bsi_next (&bsi);
}
else
return false;
}
else
return false;
}
else
return false;
}
/* If we did not find the proper negation assignment, then we can not
optimize. */
if (assign == NULL)
return false;
cond = COND_EXPR_COND (last_stmt (cond_block));
result = PHI_RESULT (phi);
/* Only relationals comparing arg[01] against zero are interesting. */
cond_code = TREE_CODE (cond);
if (cond_code != GT_EXPR && cond_code != GE_EXPR
&& cond_code != LT_EXPR && cond_code != LE_EXPR)
return false;
/* Make sure the conditional is arg[01] OP y. */
if (TREE_OPERAND (cond, 0) != rhs)
return false;
if (FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (cond, 1)))
? real_zerop (TREE_OPERAND (cond, 1))
: integer_zerop (TREE_OPERAND (cond, 1)))
;
else
return false;
/* We need to know which is the true edge and which is the false
edge so that we know if have abs or negative abs. */
extract_true_false_edges_from_block (cond_block, &true_edge, &false_edge);
/* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
will need to negate the result. Similarly for LT_EXPR/LE_EXPR if
the false edge goes to OTHER_BLOCK. */
if (cond_code == GT_EXPR || cond_code == GE_EXPR)
e = true_edge;
else
e = false_edge;
if (e->dest == other_block)
negate = true;
else
negate = false;
if (negate)
lhs = make_rename_temp (TREE_TYPE (result), NULL);
else
lhs = result;
/* Build the modify expression with abs expression. */
new = build (MODIFY_EXPR, TREE_TYPE (lhs),
lhs, build1 (ABS_EXPR, TREE_TYPE (lhs), rhs));
replace_phi_with_stmt (bsi_start (bb), bb, cond_block, phi, new);
if (negate)
{
/* Get the right BSI. We want to insert after the recently
added ABS_EXPR statement (which we know is the first statement
in the block. */
bsi = bsi_start (bb);
bsi_next (&bsi);
new = build (MODIFY_EXPR, TREE_TYPE (result),
result, build1 (NEGATE_EXPR, TREE_TYPE (lhs), lhs));
bsi_insert_after (&bsi, new, BSI_NEW_STMT);
/* Register the new statement as defining the temporary -- this is
normally done by replace_phi_with_stmt, but the link will be wrong
if we had to negate the resulting value. */
SSA_NAME_DEF_STMT (result) = new;
}
/* Note that we optimized this PHI. */
return true;
}
/* Always do these optimizations if we have SSA
trees to work on. */