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[gfortran] Patch for optimized Arithmetic IF
- From: Canqun Yang <canqun at nudt dot edu dot cn>
- To: fortran at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Tue, 2 Aug 2005 22:23:28 +0800 (HKT)
- Subject: [gfortran] Patch for optimized Arithmetic IF
- Reply-to: Canqun Yang <canqun at nudt dot edu dot cn>
Hi, all,
In case of equal labels, ARITHMETIC IF can be translated to a simple version.
E.g.
IF (a) 10, 20, 20
can be translated to
if (a < 0) goto label_10;
else goto label_20;
instead of the current one generated by GCC Fortran 95 frontend.
if (a <= 0)
{
if (a < 0) goto label_10;
else goto label_20;
}
else
goto label_20;
This patch can lead the previous optimized code, OK to apply?
Canqun Yang
Creative Compiler Research Group.
National University of Defense Technology, China.
? .trans-stmt.c.save.swp
? arith_if.diff
? t
? trans-stmt.c.save
Index: ChangeLog
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fortran/ChangeLog,v
retrieving revision 1.509
diff -c -3 -p -r1.509 ChangeLog
*** ChangeLog 1 Aug 2005 21:13:38 -0000 1.509
--- ChangeLog 2 Aug 2005 13:51:39 -0000
***************
*** 1,3 ****
--- 1,8 ----
+ 2005-08-02 Canqun Yang <canqun@nudt.edu.cn>
+
+ * trans-stmt.c (gfc_trans_arithmetic_if): Optimized in case of equal
+ labels.
+
2005-07-31 Jerry DeLisle <jvdelisle@verizon.net>
* intrinsic.texi: Add documentation for exponent, floor, and fnum and
Index: trans-stmt.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fortran/trans-stmt.c,v
retrieving revision 1.40
diff -c -3 -p -r1.40 trans-stmt.c
*** trans-stmt.c 31 Jul 2005 20:36:47 -0000 1.40
--- trans-stmt.c 2 Aug 2005 13:51:40 -0000
*************** gfc_trans_if (gfc_code * code)
*** 461,466 ****
--- 461,474 ----
}
else // cond > 0
goto label3;
+
+ An optimized version can be generated in case of equal labels.
+ E.g., if label1 is equal to label2, we can translate it to
+
+ if (cond <= 0)
+ goto label1;
+ else
+ goto label3;
*/
tree
*************** gfc_trans_arithmetic_if (gfc_code * code
*** 482,499 ****
/* Build something to compare with. */
zero = gfc_build_const (TREE_TYPE (se.expr), integer_zero_node);
! /* If (cond < 0) take branch1 else take branch2.
! First build jumps to the COND .LT. 0 and the COND .EQ. 0 cases. */
! branch1 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label));
! branch2 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label2));
!
! tmp = build2 (LT_EXPR, boolean_type_node, se.expr, zero);
! branch1 = build3_v (COND_EXPR, tmp, branch1, branch2);
!
! /* if (cond <= 0) take branch1 else take branch2. */
! branch2 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label3));
! tmp = build2 (LE_EXPR, boolean_type_node, se.expr, zero);
! branch1 = build3_v (COND_EXPR, tmp, branch1, branch2);
/* Append the COND_EXPR to the evaluation of COND, and return. */
gfc_add_expr_to_block (&se.pre, branch1);
--- 490,520 ----
/* Build something to compare with. */
zero = gfc_build_const (TREE_TYPE (se.expr), integer_zero_node);
! if (code->label->value != code->label2->value)
! {
! /* If (cond < 0) take branch1 else take branch2.
! First build jumps to the COND .LT. 0 and the COND .EQ. 0 cases. */
! branch1 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label));
! branch2 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label2));
!
! if (code->label->value != code->label3->value)
! tmp = build2 (LT_EXPR, boolean_type_node, se.expr, zero);
! else
! tmp = build2 (NE_EXPR, boolean_type_node, se.expr, zero);
!
! branch1 = build3_v (COND_EXPR, tmp, branch1, branch2);
! }
! else
! branch1 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label));
!
! if (code->label->value != code->label3->value
! && code->label2->value != code->label3->value)
! {
! /* if (cond <= 0) take branch1 else take branch2. */
! branch2 = build1_v (GOTO_EXPR, gfc_get_label_decl (code->label3));
! tmp = build2 (LE_EXPR, boolean_type_node, se.expr, zero);
! branch1 = build3_v (COND_EXPR, tmp, branch1, branch2);
! }
/* Append the COND_EXPR to the evaluation of COND, and return. */
gfc_add_expr_to_block (&se.pre, branch1);