fold-const.c (fold_mathfn_compare): New function to simplify comparisons against built-in math functions.

	* fold-const.c (fold_mathfn_compare): New function to simplify
	comparisons against built-in math functions.  Fold comparisons
	of sqrt against constants.
	(fold): Call fold_mathfn_compare when appropriate.

	* gcc.dg/builtins-6.c: New test case.

From-SVN: r64619

4 files changed, 260 insertions, 14 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7ac8fc8..2b16b1b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2003-03-20  Roger Sayle  <roger@eyesopen.com>
+
+	* fold-const.c (fold_mathfn_compare): New function to simplify
+	comparisons against built-in math functions.  Fold comparisons
+	of sqrt against constants.
+	(fold): Call fold_mathfn_compare when appropriate.
+
 2003-03-20 Richard Earnshaw  <rearnsha@arm.com>
 
 	* ifcvt.c (find_if_case_1): If we add a new bb, update the dominance
@@ -1542,24 +1549,24 @@ Sat Mar  8 14:13:35 CET 2003  Jan Hubicka  <jh@suse.cz>
 	MEM, try loading the MEM into a register and taking the low-part
 	of that, to help CSE see the use of the MEM in its true mode.
 
-2002-03-05  Tom Tromey  <tromey@redhat.com>
+2003-03-05  Tom Tromey  <tromey@redhat.com>
 
 	* config/stormy16/stormy16.h (DWARF_LINE_MIN_INSTR_LENGTH):
 	Define.
 
-2002-03-05  Nick Clifton  <nickc@cambridge.redhat.com>
+2003-03-05  Nick Clifton  <nickc@cambridge.redhat.com>
 
 	* config/stormy16/stormy16.md ("*eqbranchsi"): Remove '+' on
 	operand 2.
 	("*ineqbranchsi"): Likewise.
 
-2002-03-05  Andrew Haley  <aph@cambridge.redhat.com>
+2003-03-05  Andrew Haley  <aph@cambridge.redhat.com>
 
 	* config/stormy16/stormy16.c (xstormy16_expand_prologue): Delete
 	mem_fake_push_rtx.  Instead construct a SEQUENCE to show the
 	register store followed by a stack increment.
 
-2002-03-05  Chris Moller  <cmoller@redhat.com>
+2003-03-05  Chris Moller  <cmoller@redhat.com>
 
 	* config/stormy16/stormy16.c (REG_NEEDS_SAVE): added a term
 	to inhibit saving CARRY_REGS.
@@ -2328,7 +2335,7 @@ Mon Mar  3 19:07:21 CET 2003  Jan Hubicka  <jh@suse.cz>
 	(*tst_extzv_memqi_1_n): Likewise.
 	(a peephole2): New.
 
-2002-02-28  Richard Sandiford  <rsandifo@redhat.com>
+2003-02-28  Richard Sandiford  <rsandifo@redhat.com>
 
 	* config/mips/mips.h (CRT_CALL_STATIC_FUNCTION): Wrap in
 	#ifndef __mips16.
@@ -4123,7 +4130,7 @@ Sun Feb  9 23:54:59 CET 2003  Jan Hubicka  <jh@suse.cz>
 	simplify_binary_operation):  Deal with vector modes
 	(simplify_ternary_operation):  Deal with no-op VEC_MERGE.
 
-2002-02-09  Richard Sandiford  <rsandifo@redhat.com>
+2003-02-09  Richard Sandiford  <rsandifo@redhat.com>
 
 	* toplev.c (rest_of_compilation): Recompute register usage after
 	split_all_insns.
@@ -4489,7 +4496,7 @@ Wed Feb  5 23:12:57 CET 2003  Jan Hubicka  <jh@suse.cz>
 	* config/ia64/unwind-ia64.c: include coretypes.h, tm.h to get
 	  config/ia64/linux.h
 
-2002-02-05  Roger Sayle  <roger@eyesopen.com>
+2003-02-05  Roger Sayle  <roger@eyesopen.com>
 
 	* cfgloop.h (flow_bb_inside_loop_p): Correct prototype again.
 
@@ -4605,7 +4612,7 @@ Mon Feb  3 21:19:11 CET 2003  Jan Hubicka  <jh@suse.cz>
 	(movups/movupd/movdqu patterns): Force one of operands to not be
 	memory.
 
-2002-02-03  Roger Sayle  <roger@eyesopen.com>
+2003-02-03  Roger Sayle  <roger@eyesopen.com>
 
 	* hooks.c (hook_rtx_rtx_identity): Generic hook function that
 	takes a single rtx and returns it unmodified.
@@ -5624,11 +5631,11 @@ Sat Jan 25 21:04:33 CET 2003  Jan Hubicka  <jh@suse.cz>
 	* config/h8300/h8300.c (h8300_shift_needs_scratch_p): Update a
 	comment.
 
-2002-01-25  Richard Henderson  <rth@redhat.com>
+2003-01-25  Richard Henderson  <rth@redhat.com>
 
 	* config/m68k/m68k-none.h (ASM_SPEC): Adjust inter-option spacing.
 
-2002-01-25  Kelley Cook <kelleycook@comcast.net>
+2003-01-25  Kelley Cook <kelleycook@comcast.net>
 
 	* ggc-simple.c (debug_ggc_tree): Add PTR cast.
 
@@ -5646,7 +5653,7 @@ Sat Jan 25 21:04:33 CET 2003  Jan Hubicka  <jh@suse.cz>
 	2002-02-19  Robert Lipe  <robertlipe@usa.net>
 	* config/i386/t-sco5gas: (CRTSTUFF_T_CFLAGS_S): Delete -mcoff.
 
-2002-01-25  Roger Sayle  <roger@eyesopen.com>
+2003-01-25  Roger Sayle  <roger@eyesopen.com>
 
 	* builtins.c (purge_builtin_constant_p): Scan insn stream
 	sequentially rather than by basic block.
@@ -5656,7 +5663,7 @@ Sat Jan 25 21:04:33 CET 2003  Jan Hubicka  <jh@suse.cz>
 
 	* combine.c (simplify_comparison, case AND): Remove a redundant test.
 
-2002-01-25  Roger Sayle  <roger@eyesopen.com>
+2003-01-25  Roger Sayle  <roger@eyesopen.com>
 
 	* function.h (struct function): New field calls_constant_p.
 	(current_function_calls_constant_p): New macro for above.
@@ -5668,7 +5675,7 @@ Sat Jan 25 21:04:33 CET 2003  Jan Hubicka  <jh@suse.cz>
 	* integrate.c (expand_inline_function): Set calls_constant_p if
 	the function being inlined has calls_constant_p set.
 
-2002-01-25  Roger Sayle  <roger@eyesopen.com>
+2003-01-25  Roger Sayle  <roger@eyesopen.com>
 
 	* cse.c (fold_rtx): Instantiate CONSTANT_P_RTX to 0 when not
 	optimizing, even if flag_gcse is true.
@@ -5728,7 +5735,7 @@ Sat Jan 25 11:10:03 CET 2003  Jan Hubicka  <jh@suse.cz>
 
 	* builtins.c (fold_trunc_transparent_mathfn):  Undo accidental commit.
 
-2002-01-24  Stuart Hastings  <stuart@apple.com>
+2003-01-24  Stuart Hastings  <stuart@apple.com>
 
 	* config/i386/i386.c (x86_output_mi_thunk): Add Darwin/x86 support.
 
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 4890c17..7477269 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -112,6 +112,8 @@ static int count_cond		PARAMS ((tree, int));
 static tree fold_binary_op_with_conditional_arg
   PARAMS ((enum tree_code, tree, tree, tree, int));
 static bool fold_real_zero_addition_p	PARAMS ((tree, tree, int));
+static tree fold_mathfn_compare	PARAMS ((enum built_in_function,
+					 enum tree_code, tree, tree, tree));
 
 /* The following constants represent a bit based encoding of GCC's
    comparison operators.  This encoding simplifies transformations
@@ -4661,6 +4663,144 @@ fold_real_zero_addition_p (type, addend, negate)
   return negate && !HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (type));
 }
 
+/* Subroutine of fold() that checks comparisons of built-in math
+   functions against real constants.
+
+   FCODE is the DECL_FUNCTION_CODE of the built-in, CODE is the comparison
+   operator: EQ_EXPR, NE_EXPR, GT_EXPR, LT_EXPR, GE_EXPR or LE_EXPR.  TYPE
+   is the type of the result and ARG0 and ARG1 are the operands of the
+   comparison.  ARG1 must be a TREE_REAL_CST.
+
+   The function returns the constant folded tree if a simplification
+   can be made, and NULL_TREE otherwise.  */
+
+static tree
+fold_mathfn_compare (fcode, code, type, arg0, arg1)
+     enum built_in_function fcode;
+     enum tree_code code;
+     tree type, arg0, arg1;
+{
+  REAL_VALUE_TYPE c;
+
+  if (fcode == BUILT_IN_SQRT
+      || fcode == BUILT_IN_SQRTF
+      || fcode == BUILT_IN_SQRTL)
+    {
+      tree arg = TREE_VALUE (TREE_OPERAND (arg0, 1));
+      enum machine_mode mode = TYPE_MODE (TREE_TYPE (arg0));
+
+      c = TREE_REAL_CST (arg1);
+      if (REAL_VALUE_NEGATIVE (c))
+	{
+	  /* sqrt(x) < y is always false, if y is negative.  */
+	  if (code == EQ_EXPR || code == LT_EXPR || code == LE_EXPR)
+	    return omit_one_operand (type,
+				     convert (type, integer_zero_node),
+				     arg);
+
+	  /* sqrt(x) > y is always true, if y is negative and we
+	     don't care about NaNs, i.e. negative values of x.  */
+	  if (code == NE_EXPR || !HONOR_NANS (mode))
+	    return omit_one_operand (type,
+				     convert (type, integer_one_node),
+				     arg);
+
+	  /* sqrt(x) > y is the same as x >= 0, if y is negative.  */
+	  return fold (build (GE_EXPR, type, arg,
+			      build_real (TREE_TYPE (arg), dconst0)));
+	}
+      else if (code == GT_EXPR || code == GE_EXPR)
+	{
+	  REAL_VALUE_TYPE c2;
+
+	  REAL_ARITHMETIC (c2, MULT_EXPR, c, c);
+	  real_convert (&c2, mode, &c2);
+
+	  if (REAL_VALUE_ISINF (c2))
+	    {
+	      /* sqrt(x) > y is x == +Inf, when y is very large.  */
+	      if (HONOR_INFINITIES (mode))
+		return fold (build (EQ_EXPR, type, arg,
+				    build_real (TREE_TYPE (arg), c2)));
+
+	      /* sqrt(x) > y is always false, when y is very large
+		 and we don't care about infinities.  */
+	      return omit_one_operand (type,
+				       convert (type, integer_zero_node),
+				       arg);
+	    }
+
+	  /* sqrt(x) > c is the same as x > c*c.  */
+	  return fold (build (code, type, arg,
+			      build_real (TREE_TYPE (arg), c2)));
+	}
+      else if (code == LT_EXPR || code == LE_EXPR)
+	{
+	  REAL_VALUE_TYPE c2;
+
+	  REAL_ARITHMETIC (c2, MULT_EXPR, c, c);
+	  real_convert (&c2, mode, &c2);
+
+	  if (REAL_VALUE_ISINF (c2))
+	    {
+	      /* sqrt(x) < y is always true, when y is a very large
+		 value and we don't care about NaNs or Infinities.  */
+	      if (! HONOR_NANS (mode) && ! HONOR_INFINITIES (mode))
+		return omit_one_operand (type,
+					 convert (type, integer_one_node),
+					 arg);
+
+	      /* sqrt(x) < y is x != +Inf when y is very large and we
+		 don't care about NaNs.  */
+	      if (! HONOR_NANS (mode))
+		return fold (build (NE_EXPR, type, arg,
+				    build_real (TREE_TYPE (arg), c2)));
+
+	      /* sqrt(x) < y is x >= 0 when y is very large and we
+		 don't care about Infinities.  */
+	      if (! HONOR_INFINITIES (mode))
+		return fold (build (GE_EXPR, type, arg,
+				    build_real (TREE_TYPE (arg), dconst0)));
+
+	      /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large.  */
+	      if ((*lang_hooks.decls.global_bindings_p) () != 0
+		  || contains_placeholder_p (arg))
+		return NULL_TREE;
+
+	      arg = save_expr (arg);
+	      return fold (build (TRUTH_ANDIF_EXPR, type,
+				  fold (build (GE_EXPR, type, arg,
+					       build_real (TREE_TYPE (arg),
+							   dconst0))),
+				  fold (build (NE_EXPR, type, arg,
+					       build_real (TREE_TYPE (arg),
+							   c2)))));
+	    }
+
+	  /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs.  */
+	  if (! HONOR_NANS (mode))
+	    return fold (build (code, type, arg,
+				build_real (TREE_TYPE (arg), c2)));
+
+	  /* sqrt(x) < c is the same as x >= 0 && x < c*c.  */
+	  if ((*lang_hooks.decls.global_bindings_p) () == 0
+	      && ! contains_placeholder_p (arg))
+	    {
+	      arg = save_expr (arg);
+	      return fold (build (TRUTH_ANDIF_EXPR, type,
+				  fold (build (GE_EXPR, type, arg,
+					       build_real (TREE_TYPE (arg),
+							   dconst0))),
+				  fold (build (code, type, arg,
+					       build_real (TREE_TYPE (arg),
+							   c2)))));
+	    }
+	}
+    }
+
+  return NULL_TREE;
+}
+
 
 /* Perform constant folding and related simplification of EXPR.
    The related simplifications include x*1 => x, x*0 => 0, etc.,
@@ -6209,6 +6349,21 @@ fold (expr)
 					  arg1, TREE_OPERAND (arg0, 1), 0))
 	      && ! TREE_CONSTANT_OVERFLOW (tem))
 	    return fold (build (code, type, TREE_OPERAND (arg0, 0), tem));
+
+	  /* Fold comparisons against built-in math functions.  */
+	  if (TREE_CODE (arg1) == REAL_CST
+	      && flag_unsafe_math_optimizations
+	      && ! flag_errno_math)
+	    {
+	      enum built_in_function fcode = builtin_mathfn_code (arg0);
+
+	      if (fcode != END_BUILTINS)
+		{
+		  tem = fold_mathfn_compare (fcode, code, type, arg0, arg1);
+		  if (tem != NULL_TREE)
+		    return tem;
+		}
+	    }
 	}
 
       /* Convert foo++ == CONST into ++foo == CONST + INCR.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b1bc27d..170886f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2003-03-20  Roger Sayle  <roger@eyesopen.com>
+
+	* gcc.dg/builtins-6.c: New test case.
+
 2003-03-19  Alan Modra  <amodra@bigpond.net.au>
 
 	PR target/10073
diff --git a/gcc/testsuite/gcc.dg/builtins-6.c b/gcc/testsuite/gcc.dg/builtins-6.c
new file mode 100644
index 0000000..2ebb0b2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtins-6.c
@@ -0,0 +1,80 @@
+/* Copyright (C) 2003  Free Software Foundation.
+
+   Verify that constant folding comparisons against built-in math functions
+   don't cause any problems for the compiler, and produce expected results.
+
+   Written by Roger Sayle, 15th March 2003.  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math" } */
+
+#include <float.h>
+
+extern void abort (void);
+extern double sqrt (double);
+
+int test1(double x)
+{
+  return sqrt(x) < -9.0;
+}
+
+int test2(double x)
+{
+  return sqrt(x) > -9.0;
+}
+
+int test3(double x)
+{
+  return sqrt(x) < 9.0;
+}
+
+int test4(double x)
+{
+  return sqrt(x) > 9.0;
+}
+
+int test5(double x)
+{
+  return sqrt(x) < DBL_MAX;
+}
+
+int test6(double x)
+{
+  return sqrt(x) > DBL_MAX;
+}
+
+int main()
+{
+  double x;
+
+  x = 80.0;
+  if (test1 (x))
+    abort ();
+  if (! test2 (x))
+    abort ();
+  if (! test3 (x))
+    abort ();
+  if (test4 (x))
+    abort ();
+  if (! test5 (x))
+    abort ();
+  if (test6 (x))
+    abort ();
+
+  x = 100.0;
+  if (test1 (x))
+    abort ();
+  if (! test2 (x))
+    abort ();
+  if (test3 (x))
+    abort ();
+  if (! test4 (x))
+    abort ();
+  if (! test5 (x))
+    abort ();
+  if (test6 (x))
+    abort ();
+
+  return 0;
+}
+