So in case there's any confusion about the behaviour expected of *the vabs
intrinsic*, here's a testcase (failing without patch, passing with it)...
--Alan
Alan Lawrence wrote:
...as the former is defined as returning MIN_VALUE for argument MIN_VALUE,
whereas the latter is 'undefined', and gcc can optimize "abs(x)>=0" to "true",
which is wrong for __builtin_aarch64_abs.
There has been much debate here, although not recently - I think the last was
https://gcc.gnu.org/ml/gcc-patches/2014-05/msg00387.html . However without a
definite solution, we should at least stop the folding, as otherwise this is a bug.
The complication here is that the folding meant we never expanded the call to
__builtin_aarch64_absdi, and thus never realized that expanding would cause an
ICE: gen_absdi2() takes only two parameters (source and dest operand), and has
no parameter corresponding to the scratch operand in the insn_data; but the code
in aarch64_simd_expand_args, reads the number of arguments from the insn_data,
and so tries to get another operand from the call to __builtin_aarch64_absdi,
causing the ICE. Hence, we have to introduce a SIMD_ARG_SCRATCH, used in
aarch64_simd_expand_args to skip over the argument.
(There is an alternative way of doing this, i.e. to update the for-loop in
aarch64_simd_expand_builtin by adding yet another version of 'k'. However, I
thought there were enough versions already that I really didn't want to add one
more...)
To go with this, I've renamed qualifier_internal to qualifier_scratch, as it's
not clear that any non-scratch internal operands (whatever such might be) would
want the same treatment!
Cross-tested check-gcc on aarch64-none-elf.
Ok for trunk?
gcc/ChangeLog:
* config/aarch64/aarch64-builtins.c (enum aarch64_type_qualifiers):
Rename qualifier_internal to qualifier_scratch.
(aarch64_types_unop_qualifiers, aarch64_init_simd_builtins): Follow
renaming.
(builtin_simd_arg): New SIMD_ARG_SCRATCH enum value.
(aarch64_simd_expand_args): Skip over SIMD_ARG_SCRATCHes.
(aarch64_simd_expand_builtin): Handle qualifier_scratch.
(aarch64_fold_builtin): Remove folding of abs.
diff --git a/gcc/testsuite/gcc.target/aarch64/vabs_intrinsic_2.c b/gcc/testsuite/gcc.target/aarch64/vabs_intrinsic_2.c
new file mode 100644
index 0000000000000000000000000000000000000000..12fdd813bc3f58a183b4986c5c9c532c2b608699
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/vabs_intrinsic_2.c
@@ -0,0 +1,17 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <arm_neon.h>
+
+extern void abort (void);
+
+int
+main (int argc, char **argv)
+{
+ int8x8_t a = vabs_s8 (vdup_n_s8 (-128)); /* Should all be -128. */
+ uint8x8_t b = vcltz_s8 (a); /* Should all be true i.e. -1. */
+ if (vget_lane_u8 (b, 1))
+ return 0;
+ abort ();
+}
+
