Now that we keep track of the signbit, we can use it to fold __builtin_signbit.
I am assuming I don't have try too hard to get the actual signbit
number and 1 will do. Especially, since we're inconsistent in trunk whether
we fold the builtin or whether we calculate it at runtime.
abulafia:~$ cat a.c
float nzero = -0.0;
main(){
printf("0x%x\n", __builtin_signbit(-0.0));
printf("0x%x\n", __builtin_signbit(nzero));
}
abulafia:~$ gcc a.c -w && ./a.out
0x1
0x80000000
It is amazing that we've been failing to fold something as simple as
this:
if (x > 5.0)
num = __builtin_signbit (x);
It does the right thing now :-P.
gcc/ChangeLog:
* gimple-range-fold.cc
(fold_using_range::range_of_builtin_int_call): Add case for
CFN_BUILT_IN_SIGNBIT.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/vrp-float-signbit-1.c: New test.
---
gcc/gimple-range-fold.cc | 20 +++++++++++++++++++
.../gcc.dg/tree-ssa/vrp-float-signbit-1.c | 12 +++++++++++
2 files changed, 32 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/vrp-float-signbit-1.c
diff --git a/gcc/gimple-range-fold.cc b/gcc/gimple-range-fold.cc
index b0b22106320..d8497fc9be7 100644
--- a/gcc/gimple-range-fold.cc
+++ b/gcc/gimple-range-fold.cc
@@ -1023,6 +1023,26 @@ fold_using_range::range_of_builtin_int_call (irange &r,
gcall *call,
break;
}
+ case CFN_BUILT_IN_SIGNBIT:
+ {
+ arg = gimple_call_arg (call, 0);
+ frange tmp;
+ if (src.get_operand (tmp, arg))
+ {
+ if (tmp.get_signbit ().varying_p ())
+ return false;
+ if (tmp.get_signbit ().yes_p ())
+ {
+ tree one = build_one_cst (type);
+ r.set (one, one);
+ }
+ else
+ r.set_zero (type);
+ return true;
+ }
+ break;
+ }
+
case CFN_BUILT_IN_TOUPPER:
{
arg = gimple_call_arg (call, 0);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/vrp-float-signbit-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/vrp-float-signbit-1.c
new file mode 100644
index 00000000000..3fa783ec460
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/vrp-float-signbit-1.c
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp" }
+
+int num;
+
+void func(float x)
+{
+ if (x > 5.0)
+ num = __builtin_signbit (x);
+}
+
+// { dg-final { scan-tree-dump-times "num = 0;" 1 "evrp" } }
--
2.37.1
