toolchain: gcc: backport fixes for gcc bug 54295

Fix "Widening multiply-accumulate operation uses wrong value extension"
for 4.7, 4.7-linaro and 4.6-linaro, which backported the broken code to 4.6.
Vanilla 4.6 is unaffected.

Fixes #13420.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

SVN-Revision: 36486

1 files changed, 70 insertions, 0 deletions

diff --git a/toolchain/gcc/patches/4.7.2/020-gcc_bug_54295.patch b/toolchain/gcc/patches/4.7.2/020-gcc_bug_54295.patch
new file mode 100644
index 0000000..0d51975
--- /dev/null
+++ b/toolchain/gcc/patches/4.7.2/020-gcc_bug_54295.patch
@@ -0,0 +1,70 @@
+diff -urN a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
+--- a/gcc/tree-ssa-math-opts.c	2011-12-20 22:33:48.000000000 +0100
++++ b/gcc/tree-ssa-math-opts.c	2013-04-29 16:39:54.413585206 +0200
+@@ -1968,6 +1968,47 @@
+  }
+ };
+ 
++/* Return true if stmt is a type conversion operation that can be stripped
++   when used in a widening multiply operation.  */
++static bool
++widening_mult_conversion_strippable_p (tree result_type, gimple stmt)
++{
++  enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
++
++  if (TREE_CODE (result_type) == INTEGER_TYPE)
++    {
++      tree op_type;
++      tree inner_op_type;
++
++      if (!CONVERT_EXPR_CODE_P (rhs_code))
++	return false;
++
++      op_type = TREE_TYPE (gimple_assign_lhs (stmt));
++
++      /* If the type of OP has the same precision as the result, then
++	 we can strip this conversion.  The multiply operation will be
++	 selected to create the correct extension as a by-product.  */
++      if (TYPE_PRECISION (result_type) == TYPE_PRECISION (op_type))
++	return true;
++
++      /* We can also strip a conversion if it preserves the signed-ness of
++	 the operation and doesn't narrow the range.  */
++      inner_op_type = TREE_TYPE (gimple_assign_rhs1 (stmt));
++
++      /* If the inner-most type is unsigned, then we can strip any
++	 intermediate widening operation.  If it's signed, then the
++	 intermediate widening operation must also be signed.  */
++      if ((TYPE_UNSIGNED (inner_op_type)
++	   || TYPE_UNSIGNED (op_type) == TYPE_UNSIGNED (inner_op_type))
++	  && TYPE_PRECISION (op_type) > TYPE_PRECISION (inner_op_type))
++	return true;
++
++      return false;
++    }
++
++  return rhs_code == FIXED_CONVERT_EXPR;
++}
++
+ /* Return true if RHS is a suitable operand for a widening multiplication,
+    assuming a target type of TYPE.
+    There are two cases:
+@@ -1984,17 +2025,13 @@
+ {
+   gimple stmt;
+   tree type1, rhs1;
+-  enum tree_code rhs_code;
+ 
+   if (TREE_CODE (rhs) == SSA_NAME)
+     {
+       stmt = SSA_NAME_DEF_STMT (rhs);
+       if (is_gimple_assign (stmt))
+ 	{
+-	  rhs_code = gimple_assign_rhs_code (stmt);
+-	  if (TREE_CODE (type) == INTEGER_TYPE
+-	      ? !CONVERT_EXPR_CODE_P (rhs_code)
+-	      : rhs_code != FIXED_CONVERT_EXPR)
++	  if (! widening_mult_conversion_strippable_p (type, stmt))
+ 	    rhs1 = rhs;
+ 	  else
+ 	    {