PR tree-optimization/51396

	* tree-ssa-math-opts.c (convert_mult_to_fma): Don't optimize
	if MUL_RESULT has zero uses.

	* g++.dg/opt/pr51396.C: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@182028 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 37 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 52c1de56aef..318b4ceadb1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2011-12-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/51396
+	* tree-ssa-math-opts.c (convert_mult_to_fma): Don't optimize
+	if MUL_RESULT has zero uses.
+
 	PR debug/51410
 	* c-decl.c (pop_scope): Don't add DECL_EXTERNAL decls
 	for debug info if scope is file_scope.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 654a56ea806..efb2ed42af3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2011-12-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/51396
+	* g++.dg/opt/pr51396.C: New test.
+
 	PR debug/51410
 	* gcc.dg/debug/dwarf2/pr51410.c: New test.
 
diff --git a/gcc/testsuite/g++.dg/opt/pr51396.C b/gcc/testsuite/g++.dg/opt/pr51396.C
new file mode 100644
index 00000000000..f2b21b60d53
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr51396.C
@@ -0,0 +1,24 @@
+// PR tree-optimization/51396
+// { dg-do compile }
+// { dg-options "-O2 -fnon-call-exceptions -mfma" }
+// { dg-options "-O2 -fnon-call-exceptions -mfma" { target i?86-*-* x86_64-*-* } }
+
+double baz (double) throw ();
+
+struct C
+{
+  C (double d = 0.0) : c (d) {}
+  double c;
+};
+
+static inline void
+foo (double x, const C &y)
+{
+  x ? (y.c * baz (x)) : (C (), y);
+}
+
+void
+bar (double x, C y)
+{
+  foo (x, y);
+}
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 75abb3369a1..06a4505079f 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -2429,6 +2429,12 @@ convert_mult_to_fma (gimple mul_stmt, tree op1, tree op2)
   if (optab_handler (fma_optab, TYPE_MODE (type)) == CODE_FOR_nothing)
     return false;
 
+  /* If the multiplication has zero uses, it is kept around probably because
+     of -fnon-call-exceptions.  Don't optimize it away in that case,
+     it is DCE job.  */
+  if (has_zero_uses (mul_result))
+    return false;
+
   /* Make sure that the multiplication statement becomes dead after
      the transformation, thus that all uses are transformed to FMAs.
      This means we assume that an FMA operation has the same cost