This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PATCH] Optimize pow(x,0.0) = pow(1.0,y) = 1.0
- From: Roger Sayle <roger at www dot eyesopen dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 20 Feb 2003 21:10:14 -0700 (MST)
- Subject: [PATCH] Optimize pow(x,0.0) = pow(1.0,y) = 1.0
The following patch implements the built-in constant folding optimizations
that "pow(x,0.0) = 1.0" and "pow(1.0,y) = 1.0", even when x and/or y are
NaN. There are plenty more optimizations to come, but the patch below is
large enough as it is.
Firstly, this patch exports the function "omit_one_operand" from
fold-const.c (so that it can be used in builtins.c). The prototype
is added to tree.h, and whilst I was there I moved the prototype for
div_and_round_double so that all the fold-const.c functions were in
a single place.
Next, I modified builtin_mathfn_code to also handle the binary math
built-ins, such as pow and atan2. This extended functionality isn't
used yet but will be in follow-up patches.
The actual optimizations themselves are quite straight forward, but
by introducing the variable "type" to hold the function's return type,
it turned out that much of the code in fold_builtin could be simplified.
The following patch has been tested on i686-pc-linux-gnu, with a full
"make bootstrap", all languages except Ada and treelang, and a complete
"make -k check" with no new regressions in the testsuite. I've also
added a new test to gcc.dg that confirms the optimization is performed.
Ok for mainline?
2003-02-20 Roger Sayle <roger at eyesopen dot com>
* fold-const.c (omit_one_operand): No longer static.
* tree.h (omit_one_operand): Prototype here.
(div_and_round_double): Keep fold-const.c prototypes together.
* builtins.c (builtin_mathfn_code): Handle binary built-in
funtions, such as "pow" and "atan2".
(fold_builtin): Optimize both pow(x,0.0) and pow(1.0,y) to 1.0.
Simplify optimizations using "type" the builtin's return type.
* gcc.dg/builtins-5.c: New test case.
Index: fold-const.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fold-const.c,v
retrieving revision 1.237
diff -c -3 -p -r1.237 fold-const.c
*** fold-const.c 19 Feb 2003 22:59:33 -0000 1.237
--- fold-const.c 20 Feb 2003 15:19:13 -0000
*************** static int truth_value_p PARAMS ((enum t
*** 81,87 ****
static int operand_equal_for_comparison_p PARAMS ((tree, tree, tree));
static int twoval_comparison_p PARAMS ((tree, tree *, tree *, int *));
static tree eval_subst PARAMS ((tree, tree, tree, tree, tree));
- static tree omit_one_operand PARAMS ((tree, tree, tree));
static tree pedantic_omit_one_operand PARAMS ((tree, tree, tree));
static tree distribute_bit_expr PARAMS ((enum tree_code, tree, tree, tree));
static tree make_bit_field_ref PARAMS ((tree, tree, int, int, int));
--- 81,86 ----
*************** eval_subst (arg, old0, new0, old1, new1)
*** 2256,2262 ****
If OMITTED has side effects, we must evaluate it. Otherwise, just do
the conversion of RESULT to TYPE. */
! static tree
omit_one_operand (type, result, omitted)
tree type, result, omitted;
{
--- 2255,2261 ----
If OMITTED has side effects, we must evaluate it. Otherwise, just do
the conversion of RESULT to TYPE. */
! tree
omit_one_operand (type, result, omitted)
tree type, result, omitted;
{
Index: tree.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree.h,v
retrieving revision 1.381
diff -c -3 -p -r1.381 tree.h
*** tree.h 12 Feb 2003 21:48:58 -0000 1.381
--- tree.h 20 Feb 2003 15:19:14 -0000
***************
*** 1,6 ****
/* Front-end tree definitions for GNU compiler.
Copyright (C) 1989, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
! 2001, 2002 Free Software Foundation, Inc.
This file is part of GCC.
--- 1,6 ----
/* Front-end tree definitions for GNU compiler.
Copyright (C) 1989, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
! 2001, 2002, 2003 Free Software Foundation, Inc.
This file is part of GCC.
*************** extern void rrotate_double PARAMS ((unsi
*** 2909,2915 ****
--- 2909,2927 ----
HOST_WIDE_INT, unsigned int,
unsigned HOST_WIDE_INT *,
HOST_WIDE_INT *));
+
+ extern int div_and_round_double PARAMS ((enum tree_code, int,
+ unsigned HOST_WIDE_INT,
+ HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT,
+ HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT *,
+ HOST_WIDE_INT *,
+ unsigned HOST_WIDE_INT *,
+ HOST_WIDE_INT *));
+
extern int operand_equal_p PARAMS ((tree, tree, int));
+ extern tree omit_one_operand PARAMS ((tree, tree, tree));
extern tree invert_truthvalue PARAMS ((tree));
/* In builtins.c */
*************** extern int supports_one_only PARAMS ((v
*** 3056,3072 ****
extern void variable_section PARAMS ((tree, int));
enum tls_model decl_tls_model PARAMS ((tree));
enum symbol_visibility decl_visibility PARAMS ((tree));
-
- /* In fold-const.c */
- extern int div_and_round_double PARAMS ((enum tree_code, int,
- unsigned HOST_WIDE_INT,
- HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
- HOST_WIDE_INT,
- unsigned HOST_WIDE_INT *,
- HOST_WIDE_INT *,
- unsigned HOST_WIDE_INT *,
- HOST_WIDE_INT *));
/* In stmt.c */
extern void emit_nop PARAMS ((void));
--- 3068,3073 ----
Index: builtins.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/builtins.c,v
retrieving revision 1.177
diff -c -3 -p -r1.177 builtins.c
*** builtins.c 11 Feb 2003 21:15:26 -0000 1.177
--- builtins.c 20 Feb 2003 15:19:16 -0000
*************** builtin_mathfn_code (t)
*** 4512,4521 ****
arglist = TREE_OPERAND (t, 1);
if (! arglist
! || TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) != REAL_TYPE
! || TREE_CHAIN (arglist))
return END_BUILTINS;
return DECL_FUNCTION_CODE (fndecl);
}
--- 4512,4541 ----
arglist = TREE_OPERAND (t, 1);
if (! arglist
! || TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) != REAL_TYPE)
return END_BUILTINS;
+ arglist = TREE_CHAIN (arglist);
+ switch (DECL_FUNCTION_CODE (fndecl))
+ {
+ case BUILT_IN_POW:
+ case BUILT_IN_POWF:
+ case BUILT_IN_POWL:
+ case BUILT_IN_ATAN2:
+ case BUILT_IN_ATAN2F:
+ case BUILT_IN_ATAN2L:
+ if (! arglist
+ || TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) != REAL_TYPE
+ || TREE_CHAIN (arglist))
+ return END_BUILTINS;
+ break;
+
+ default:
+ if (arglist)
+ return END_BUILTINS;
+ break;
+ }
+
return DECL_FUNCTION_CODE (fndecl);
}
*************** fold_builtin (exp)
*** 4650,4655 ****
--- 4670,4676 ----
{
tree fndecl = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
tree arglist = TREE_OPERAND (exp, 1);
+ tree type = TREE_TYPE (TREE_TYPE (fndecl));
enum built_in_function fcode = DECL_FUNCTION_CODE (fndecl);
if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_MD)
*************** fold_builtin (exp)
*** 4693,4702 ****
REAL_VALUE_TYPE r, x;
x = TREE_REAL_CST (arg);
! mode = TYPE_MODE (TREE_TYPE (arg));
if (real_sqrt (&r, mode, &x)
|| (!flag_trapping_math && !flag_errno_math))
! return build_real (TREE_TYPE (arg), r);
}
/* Optimize sqrt(exp(x)) = exp(x/2.0). */
--- 4714,4723 ----
REAL_VALUE_TYPE r, x;
x = TREE_REAL_CST (arg);
! mode = TYPE_MODE (type);
if (real_sqrt (&r, mode, &x)
|| (!flag_trapping_math && !flag_errno_math))
! return build_real (type, r);
}
/* Optimize sqrt(exp(x)) = exp(x/2.0). */
*************** fold_builtin (exp)
*** 4707,4715 ****
|| fcode == BUILT_IN_EXPL))
{
tree expfn = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
! arg = build (RDIV_EXPR, TREE_TYPE (arg),
TREE_VALUE (TREE_OPERAND (arg, 1)),
! build_real (TREE_TYPE (arg), dconst2));
arglist = build_tree_list (NULL_TREE, arg);
return build_function_call_expr (expfn, arglist);
}
--- 4728,4736 ----
|| fcode == BUILT_IN_EXPL))
{
tree expfn = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
! arg = build (RDIV_EXPR, type,
TREE_VALUE (TREE_OPERAND (arg, 1)),
! build_real (type, dconst2));
arglist = build_tree_list (NULL_TREE, arg);
return build_function_call_expr (expfn, arglist);
}
*************** fold_builtin (exp)
*** 4726,4732 ****
/* Optimize exp(0.0) = 1.0. */
if (real_zerop (arg))
! return build_real (TREE_TYPE (arg), dconst1);
/* Optimize exp(log(x)) = x. */
fcode = builtin_mathfn_code (arg);
--- 4747,4753 ----
/* Optimize exp(0.0) = 1.0. */
if (real_zerop (arg))
! return build_real (type, dconst1);
/* Optimize exp(log(x)) = x. */
fcode = builtin_mathfn_code (arg);
*************** fold_builtin (exp)
*** 4748,4754 ****
/* Optimize log(1.0) = 0.0. */
if (real_onep (arg))
! return build_real (TREE_TYPE (arg), dconst0);
/* Optimize log(exp(x)) = x. */
fcode = builtin_mathfn_code (arg);
--- 4769,4775 ----
/* Optimize log(1.0) = 0.0. */
if (real_onep (arg))
! return build_real (type, dconst0);
/* Optimize log(exp(x)) = x. */
fcode = builtin_mathfn_code (arg);
*************** fold_builtin (exp)
*** 4766,4796 ****
{
tree logfn = build_function_call_expr (fndecl,
TREE_OPERAND (arg, 1));
! return fold (build (RDIV_EXPR, TREE_TYPE (arg), logfn,
! build_real (TREE_TYPE (arg), dconst2)));
}
}
break;
case BUILT_IN_INF:
case BUILT_IN_INFF:
case BUILT_IN_INFL:
! return fold_builtin_inf (TREE_TYPE (TREE_TYPE (fndecl)), true);
case BUILT_IN_HUGE_VAL:
case BUILT_IN_HUGE_VALF:
case BUILT_IN_HUGE_VALL:
! return fold_builtin_inf (TREE_TYPE (TREE_TYPE (fndecl)), false);
case BUILT_IN_NAN:
case BUILT_IN_NANF:
case BUILT_IN_NANL:
! return fold_builtin_nan (arglist, TREE_TYPE (TREE_TYPE (fndecl)), true);
case BUILT_IN_NANS:
case BUILT_IN_NANSF:
case BUILT_IN_NANSL:
! return fold_builtin_nan (arglist, TREE_TYPE (TREE_TYPE (fndecl)), false);
case BUILT_IN_FLOOR:
case BUILT_IN_FLOORF:
--- 4787,4835 ----
{
tree logfn = build_function_call_expr (fndecl,
TREE_OPERAND (arg, 1));
! return fold (build (RDIV_EXPR, type, logfn,
! build_real (type, dconst2)));
}
}
break;
+ case BUILT_IN_POW:
+ case BUILT_IN_POWF:
+ case BUILT_IN_POWL:
+ if (validate_arglist (arglist, REAL_TYPE, REAL_TYPE, VOID_TYPE))
+ {
+ tree arg0 = TREE_VALUE (arglist);
+ tree arg1 = TREE_VALUE (TREE_CHAIN (arglist));
+
+ /* Optimize pow(x,0.0) = 1.0. */
+ if (real_zerop (arg1))
+ return omit_one_operand (type, build_real (type, dconst1), arg0);
+
+ /* Optimize pow(1.0,y) = 1.0. */
+ if (real_onep (arg0))
+ return omit_one_operand (type, build_real (type, dconst1), arg1);
+ }
+ break;
+
case BUILT_IN_INF:
case BUILT_IN_INFF:
case BUILT_IN_INFL:
! return fold_builtin_inf (type, true);
case BUILT_IN_HUGE_VAL:
case BUILT_IN_HUGE_VALF:
case BUILT_IN_HUGE_VALL:
! return fold_builtin_inf (type, false);
case BUILT_IN_NAN:
case BUILT_IN_NANF:
case BUILT_IN_NANL:
! return fold_builtin_nan (arglist, type, true);
case BUILT_IN_NANS:
case BUILT_IN_NANSF:
case BUILT_IN_NANSL:
! return fold_builtin_nan (arglist, type, false);
case BUILT_IN_FLOOR:
case BUILT_IN_FLOORF:
*** /dev/null Thu Aug 30 14:30:55 2001
--- gcc.dg/builtins-5.c Thu Feb 20 20:09:45 2003
***************
*** 0 ****
--- 1,45 ----
+ /* Copyright (C) 2003 Free Software Foundation.
+
+ Verify that built-in math function constant folding of constant
+ arguments is correctly performed by the by the compiler.
+
+ Written by Roger Sayle, 20th February 2003. */
+
+ /* { dg-do link } */
+ /* { dg-options "-O2 -ffast-math" } */
+
+ extern void link_error(void);
+
+ void test(double x)
+ {
+ if (pow (x, 0.0) != 1.0)
+ link_error ();
+ if (pow (1.0, x) != 1.0)
+ link_error ();
+ }
+
+ void testf(float x)
+ {
+ if (powf (x, 0.0f) != 1.0f)
+ link_error ();
+ if (powf (1.0f, x) != 1.0f)
+ link_error ();
+ }
+
+ void testl(long double x)
+ {
+ if (powl (x, 0.0l) != 1.0l)
+ link_error ();
+ if (powl (1.0l, x) != 1.0l)
+ link_error ();
+ }
+
+ int main()
+ {
+ test (0.0);
+ testf (0.0f);
+ testl (0.0l);
+
+ return 0;
+ }
+
Roger
--
Roger Sayle, E-mail: roger at eyesopen dot com
OpenEye Scientific Software, WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road, Tel: (+1) 505-473-7385
Santa Fe, New Mexico, 87507. Fax: (+1) 505-473-0833