Hi all, Here's a new version of the patch.
> >>> " If an exceptional condition occurs during the evaluation of an
> >>> expression
> >> (that is, if the result is not mathematically defined or not in the
> >> range of representable values for its type), the behavior is undefined."
> >>>
> >>> So it should still be acceptable to do in this case.
> >>
> >> -fwrapv
> >
> > If I understand correctly, you're happy with this is I guard it on !
> > flag_wrapv ?
>
> I did some more digging. Right shift of a negative value is IMP_DEF (not
> UNDEF - this keeps catching me out). So yes, wrapping this with !wrapv
> would address my concern.
>
> I've not reviewed the patch itself, though. I've never even written a patch
> for match.pd, so don't feel qualified to do that.
No problem, thanks for catching this! I'm sure one of the Richards will review
it when
they have a chance.
Bootstrapped Regtested on aarch64-none-linux-gnu,
x86_64-pc-linux-gnu and no regressions.
Ok for master?
Thanks,
Tamar
gcc/ChangeLog:
* match.pd: New negate+shift pattern.
gcc/testsuite/ChangeLog:
* gcc.dg/signbit-2.c: New test.
* gcc.dg/signbit-3.c: New test.
* gcc.target/aarch64/signbit-1.c: New test.
--- inline copy of patch ---
diff --git a/gcc/match.pd b/gcc/match.pd
index
7d2a24dbc5e9644a09968f877e12a824d8ba1caa..3d48eda826f889483a83267409c3f278ee907b57
100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -826,6 +826,38 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
{ tree utype = unsigned_type_for (type); }
(convert (rshift (lshift (convert:utype @0) @2) @3))))))
+/* Fold (-x >> C) into x > 0 where C = precision(type) - 1. */
+(for cst (INTEGER_CST VECTOR_CST)
+ (simplify
+ (rshift (negate:s @0) cst@1)
+ (if (!flag_wrapv)
+ (with { tree ctype = TREE_TYPE (@0);
+ tree stype = TREE_TYPE (@1);
+ tree bt = truth_type_for (ctype); }
+ (switch
+ /* Handle scalar case. */
+ (if (INTEGRAL_TYPE_P (ctype)
+ && !VECTOR_TYPE_P (ctype)
+ && !TYPE_UNSIGNED (ctype)
+ && canonicalize_math_after_vectorization_p ()
+ && wi::eq_p (wi::to_wide (@1), TYPE_PRECISION (stype) - 1))
+ (convert:bt (gt:bt @0 { build_zero_cst (stype); })))
+ /* Handle vector case with a scalar immediate. */
+ (if (VECTOR_INTEGER_TYPE_P (ctype)
+ && !VECTOR_TYPE_P (stype)
+ && !TYPE_UNSIGNED (ctype)
+ && wi::eq_p (wi::to_wide (@1), TYPE_PRECISION (stype) - 1))
+ (convert:bt (gt:bt @0 { build_zero_cst (ctype); })))
+ /* Handle vector case with a vector immediate. */
+ (if (VECTOR_INTEGER_TYPE_P (ctype)
+ && VECTOR_TYPE_P (stype)
+ && !TYPE_UNSIGNED (ctype)
+ && uniform_vector_p (@1))
+ (with { tree cst = vector_cst_elt (@1, 0);
+ tree t = TREE_TYPE (cst); }
+ (if (wi::eq_p (wi::to_wide (cst), TYPE_PRECISION (t) - 1))
+ (convert:bt (gt:bt @0 { build_zero_cst (ctype); }))))))))))
+
/* Fold (C1/X)*C2 into (C1*C2)/X. */
(simplify
(mult (rdiv@3 REAL_CST@0 @1) REAL_CST@2)
diff --git a/gcc/testsuite/gcc.dg/signbit-2.c b/gcc/testsuite/gcc.dg/signbit-2.c
new file mode 100644
index
0000000000000000000000000000000000000000..fc0157cbc5c7996b481f2998bc30176c96a669bb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/signbit-2.c
@@ -0,0 +1,19 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps -fdump-tree-optimized" } */
+
+#include <stdint.h>
+
+void fun1(int32_t *x, int n)
+{
+ for (int i = 0; i < (n & -16); i++)
+ x[i] = (-x[i]) >> 31;
+}
+
+void fun2(int32_t *x, int n)
+{
+ for (int i = 0; i < (n & -16); i++)
+ x[i] = (-x[i]) >> 30;
+}
+
+/* { dg-final { scan-tree-dump-times {\s+>\s+\{ 0, 0, 0, 0 \}} 1 optimized } }
*/
+/* { dg-final { scan-tree-dump-not {\s+>>\s+31} optimized } } */
diff --git a/gcc/testsuite/gcc.dg/signbit-3.c b/gcc/testsuite/gcc.dg/signbit-3.c
new file mode 100644
index
0000000000000000000000000000000000000000..19e9c06c349b3287610f817628f00938ece60bf7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/signbit-3.c
@@ -0,0 +1,13 @@
+/* { dg-do assemble } */
+/* { dg-options "-O1 --save-temps -fdump-tree-optimized" } */
+
+#include <stdint.h>
+
+void fun1(int32_t *x, int n)
+{
+ for (int i = 0; i < (n & -16); i++)
+ x[i] = (-x[i]) >> 31;
+}
+
+/* { dg-final { scan-tree-dump-times {\s+>\s+0;} 1 optimized } } */
+/* { dg-final { scan-tree-dump-not {\s+>>\s+31} optimized } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/signbit-1.c
b/gcc/testsuite/gcc.target/aarch64/signbit-1.c
new file mode 100644
index
0000000000000000000000000000000000000000..3ebfb0586f37de29cf58635b27fe48503714447e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/signbit-1.c
@@ -0,0 +1,18 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps" } */
+
+#include <stdint.h>
+
+void fun1(int32_t *x, int n)
+{
+ for (int i = 0; i < (n & -16); i++)
+ x[i] = (-x[i]) >> 31;
+}
+
+void fun2(int32_t *x, int n)
+{
+ for (int i = 0; i < (n & -16); i++)
+ x[i] = (-x[i]) >> 30;
+}
+
+/* { dg-final { scan-assembler-times {\tcmgt\t} 1 } } */
rb14918.patch
Description: rb14918.patch
