re PR tree-optimization/48067 (FMA with no add operand produced by convert_mul_to_fma)

2011-03-11  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/48067
	* tree-ssa-math-opts.c (convert_mult_to_fma): Verify the
	multiplication result will be only used once on the target
	stmt.

	* gcc.dg/pr48067.c: New testcase.

From-SVN: r170877

gcc/ChangeLog

 2011-03-11  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/48067
+	* tree-ssa-math-opts.c (convert_mult_to_fma): Verify the
+	multiplication result will be only used once on the target
+	stmt.
+
+2011-03-11  Richard Guenther  <rguenther@suse.de>
+
 	* doc/invoke.texi (max-inline-insns-single): Adjust default value.
 
 2011-03-11  Richard Guenther  <rguenther@suse.de>

gcc/testsuite/ChangeLog

 2011-03-11  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/48067
+	* gcc.dg/pr48067.c: New testcase.
+
+2011-03-11  Richard Guenther  <rguenther@suse.de>
+
 	PR lto/48073
 	* g++.dg/lto/20110311-1_0.C: New testcase.
 

gcc/testsuite/gcc.dg/pr48067.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -ffast-math -fno-tree-forwprop -fno-tree-reassoc" } */
+/* { dg-options "-O2 -ffast-math -fno-tree-forwprop -fno-tree-reassoc -mfma4" { target x86_64-*-* i?86-*-* } } */
+
+float
+foo (float x, float cim)
+{
+  float c = x * cim;
+  float d = -c;
+  return c - d;
+}

gcc/tree-ssa-math-opts.c

@@ -1557,6 +1557,9 @@ convert_mult_to_fma (gimple mul_stmt, tree op1, tree op2)
       /* A negate on the multiplication leads to FNMA.  */
       if (use_code == NEGATE_EXPR)
 	{
+	  ssa_op_iter iter;
+	  tree use;
+
 	  result = gimple_assign_lhs (use_stmt);
 
 	  /* Make sure the negate statement becomes dead with this
@@ -1565,6 +1568,11 @@ convert_mult_to_fma (gimple mul_stmt, tree op1, tree op2)
 			       &use_p, &neguse_stmt))
 	    return false;
 
+	  /* Make sure the multiplication isn't also used on that stmt.  */
+	  FOR_EACH_SSA_TREE_OPERAND (use, neguse_stmt, iter, SSA_OP_USE)
+	    if (use == mul_result)
+	      return false;
+
 	  /* Re-validate.  */
 	  use_stmt = neguse_stmt;
 	  if (gimple_bb (use_stmt) != gimple_bb (mul_stmt))