Hello,
This patch improves the some_nonzerop(tree t) function from tree-complex.c file
(the function is only used there).
This function returns true if a tree as a parameter is not the constant 0 (or
+0.0 only for reals when !flag_signed_zeros ). The former result is then used
to determine if some simplifications are possible for complex expansions
(addition, multiplication, and division).
Unfortunately, if the tree is a real constant, the function always return true,
even for +0.0 because of the explicit test on flag_signed_zeros (so if your
system enables signed zeros you cannot benefit from those simplifications). To
avoid this behavior and allow complex expansion simplifications, I propose the
following patch, which test for the sign of the real constant 0.0 instead of
checking the flag.
This first fix reveals a bug (thanks to c-c++-common/torture/complex-sign-add.c
) in the simplification section of expand_complex_addition (also fixed in the
patch).
The patch has passed bootstrap and testing on x86_64-pc-linux-gnu .
Best regards,
Laurent Thévenoux
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2191d62..a6124ce 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2017-10-05 Laurent Thévenoux <laurent.theven...@inria.fr>
+
+ * tree-complex.c (some_nonzerop): Adjust the way of testing real
+ constants. Allows existing simplifications of complex expansions
+ to be well done.
+ * tree-complex.c (expand_complex_addition): Bug fixing for complex
+ addition expansion simplification.
+
2017-10-02 Bill Schmidt <wschm...@linux.vnet.ibm.com>
Backport from mainline
diff --git a/gcc/tree-complex.c b/gcc/tree-complex.c
index e0dd3d9..413b601 100644
--- a/gcc/tree-complex.c
+++ b/gcc/tree-complex.c
@@ -110,8 +110,11 @@ some_nonzerop (tree t)
/* Operations with real or imaginary part of a complex number zero
cannot be treated the same as operations with a real or imaginary
operand if we care about the signs of zeros in the result. */
- if (TREE_CODE (t) == REAL_CST && !flag_signed_zeros)
- zerop = real_identical (&TREE_REAL_CST (t), &dconst0);
+ if (TREE_CODE (t) == REAL_CST)
+ {
+ if (real_identical (&TREE_REAL_CST (t), &dconst0))
+ zerop = !real_isneg (&TREE_REAL_CST (t));
+ }
else if (TREE_CODE (t) == FIXED_CST)
zerop = fixed_zerop (t);
else if (TREE_CODE (t) == INTEGER_CST)
@@ -937,7 +940,7 @@ expand_complex_addition (gimple_stmt_iterator *gsi, tree inner_type,
case PAIR (VARYING, ONLY_REAL):
rr = gimplify_build2 (gsi, code, inner_type, ar, br);
- ri = ai;
+ ri = bi;
break;
case PAIR (VARYING, ONLY_IMAG):
