https://gcc.gnu.org/g:4f61ae081d694d3a1e99b45680f3af25ab17e3a8
commit r12-10986-g4f61ae081d694d3a1e99b45680f3af25ab17e3a8
Author: Richard Sandiford <richard.sandif...@arm.com>
Date: Tue Mar 11 15:51:54 2025 +0000
aarch64: Fix folding of degenerate svwhilele case [PR117045]
The svwhilele folder mishandled the degenerate case in which
the second argument is the maximum integer. In that case,
the result is all-true regardless of the first parameter:
If the second scalar operand is equal to the maximum signed integer
value then a condition which includes an equality test can never fail
and the result will be an all-true predicate.
This is because the conceptual "increment the first operand
by 1 after each element" is done modulo the range of the operand.
The GCC code was instead treating it as infinite precision.
whilele_5.c even had a test for the incorrect behaviour.
The easiest fix seemed to be to handle that case specially before
doing constant folding. This also copes with variable first operands.
gcc/
PR target/116999
PR target/117045
* config/aarch64/aarch64-sve-builtins-base.cc
(svwhilelx_impl::fold): Check for WHILELTs of the minimum value
and WHILELEs of the maximum value. Fold them to all-false and
all-true respectively.
gcc/testsuite/
PR target/116999
PR target/117045
* gcc.target/aarch64/sve/acle/general/whilele_5.c: Fix bogus
expected result.
* gcc.target/aarch64/sve/acle/general/whilele_11.c: New test.
* gcc.target/aarch64/sve/acle/general/whilele_12.c: Likewise.
(cherry picked from commit 50e7c51b0a0e9dc1d93f829016ae743b4f2e5070)
Diff:
---
gcc/config/aarch64/aarch64-sve-builtins-base.cc | 11 ++++++-
.../aarch64/sve/acle/general/whilele_11.c | 31 ++++++++++++++++++++
.../aarch64/sve/acle/general/whilele_12.c | 34 ++++++++++++++++++++++
.../aarch64/sve/acle/general/whilele_5.c | 2 +-
4 files changed, 76 insertions(+), 2 deletions(-)
diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index f96cb3ccc7bf..a3fc474f92ed 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -2412,7 +2412,9 @@ public:
: while_comparison (unspec_for_sint, unspec_for_uint), m_eq_p (eq_p)
{}
- /* Try to fold a call by treating its arguments as constants of type T. */
+ /* Try to fold a call by treating its arguments as constants of type T.
+ We have already filtered out the degenerate cases of X .LT. MIN
+ and X .LE. MAX. */
template<typename T>
gimple *
fold_type (gimple_folder &f) const
@@ -2465,6 +2467,13 @@ public:
gimple *
fold (gimple_folder &f) const OVERRIDE
{
+ /* Filter out cases where the condition is always true or always false. */
+ tree arg1 = gimple_call_arg (f.call, 1);
+ if (!m_eq_p && operand_equal_p (arg1, TYPE_MIN_VALUE (TREE_TYPE (arg1))))
+ return f.fold_to_pfalse ();
+ if (m_eq_p && operand_equal_p (arg1, TYPE_MAX_VALUE (TREE_TYPE (arg1))))
+ return f.fold_to_ptrue ();
+
if (f.type_suffix (1).unsigned_p)
return fold_type<poly_uint64> (f);
else
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_11.c
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_11.c
new file mode 100644
index 000000000000..2be9dc5c5347
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_11.c
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <arm_sve.h>
+#include <limits.h>
+
+svbool_t
+f1 (volatile int32_t *ptr)
+{
+ return svwhilelt_b8_s32 (*ptr, INT32_MIN);
+}
+
+svbool_t
+f2 (volatile uint32_t *ptr)
+{
+ return svwhilelt_b16_u32 (*ptr, 0);
+}
+
+svbool_t
+f3 (volatile int64_t *ptr)
+{
+ return svwhilelt_b32_s64 (*ptr, INT64_MIN);
+}
+
+svbool_t
+f4 (volatile uint64_t *ptr)
+{
+ return svwhilelt_b64_u64 (*ptr, 0);
+}
+
+/* { dg-final { scan-assembler-times {\tpfalse\tp[0-9]+\.b\n} 4 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_12.c
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_12.c
new file mode 100644
index 000000000000..713065c31453
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_12.c
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <arm_sve.h>
+#include <limits.h>
+
+svbool_t
+f1 (volatile int32_t *ptr)
+{
+ return svwhilele_b8_s32 (*ptr, INT32_MAX);
+}
+
+svbool_t
+f2 (volatile uint32_t *ptr)
+{
+ return svwhilele_b16_u32 (*ptr, UINT32_MAX);
+}
+
+svbool_t
+f3 (volatile int64_t *ptr)
+{
+ return svwhilele_b32_s64 (*ptr, INT64_MAX);
+}
+
+svbool_t
+f4 (volatile uint64_t *ptr)
+{
+ return svwhilele_b64_u64 (*ptr, UINT64_MAX);
+}
+
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.b(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.h(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.s(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.d(?:, all)\n} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_5.c
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_5.c
index ada958b29c1e..dac4515cf40d 100644
--- a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_5.c
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_5.c
@@ -28,7 +28,7 @@ test3 (svbool_t *ptr)
*ptr = svwhilele_b16_s32 (0x7ffffffb, 0x7fffffff);
}
-/* { dg-final { scan-assembler {\tptrue\tp[0-7]\.h, vl5\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.h(?:, all)\n} } } */
void
test4 (svbool_t *ptr)
