Hi,
In PR120922 we first disabled setting a range on niters_vector for
partial vectorization and later introduced a ceiling division instead.
In PR121985 we ran into this again where a bogus range caused wrong code
later. On top I saw several instances of this issue on a local branch
that enables more VLS length-controlled loops.
I believe we must not set niter_vector's range to TYPE_MAX / VF, no
matter the rounding due to the way niters_vector is used. It's not
really identical to the number of vector iterations but the actual
number the loop will iterate is niters_vector / step where step = VF
for partial vectors.
Thus, only set the range to TYPE_MAX / VF if step == 1.
Bootstrapped and regtested on x86 and power10, regtested on aarch64 and
riscv64.
Regards
Robin
gcc/ChangeLog:
PR middle-end/121985
* tree-vect-loop-manip.cc (vect_gen_vector_loop_niters): Only
set niter_vector's range if step == 1.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rvv/autovec/pr121985.c: New test.
---
.../gcc.target/riscv/rvv/autovec/pr121985.c | 17 +++++++++++++
gcc/tree-vect-loop-manip.cc | 25 ++++++-------------
2 files changed, 24 insertions(+), 18 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr121985.c
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr121985.c
b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr121985.c
new file mode 100644
index 00000000000..6e5cdd927b6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr121985.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -march=rv64gcv_zvl512b -mabi=lp64d -mrvv-max-lmul=m8" } */
+
+unsigned short a=3;
+char f=1;
+
+int main()
+{
+ for (char var=f; var<6; var++)
+ a *= 5;
+
+ return a;
+}
+
+/* We would set a wrong niter range that would cause us to extract the wrong
+ element. */
+/* { dg-final { scan-assembler-not "vslidedown.vi.*,0" } } */
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 6af07efe68a..87ad7ee5bca 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -2850,29 +2850,18 @@ vect_gen_vector_loop_niters (loop_vec_info loop_vinfo,
tree niters,
we set range information to make niters analyzer's life easier.
Note the number of latch iteration value can be TYPE_MAX_VALUE so
we have to represent the vector niter TYPE_MAX_VALUE + 1 / vf. */
- if (stmts != NULL && const_vf > 0 && !LOOP_VINFO_EPILOGUE_P (loop_vinfo))
+ if (stmts != NULL
+ && integer_onep (step_vector))
{
- if (niters_no_overflow
- && LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo))
- {
- int_range<1> vr (type,
- wi::one (TYPE_PRECISION (type)),
- wi::div_ceil (wi::max_value
- (TYPE_PRECISION (type),
- TYPE_SIGN (type)),
- const_vf,
- TYPE_SIGN (type)));
- set_range_info (niters_vector, vr);
- }
- else if (niters_no_overflow)
+ if (niters_no_overflow)
{
int_range<1> vr (type,
wi::one (TYPE_PRECISION (type)),
wi::div_trunc (wi::max_value
- (TYPE_PRECISION (type),
- TYPE_SIGN (type)),
- const_vf,
- TYPE_SIGN (type)));
+ (TYPE_PRECISION (type),
+ TYPE_SIGN (type)),
+ const_vf,
+ TYPE_SIGN (type)));
set_range_info (niters_vector, vr);
}
/* For VF == 1 the vector IV might also overflow so we cannot
--
2.51.0
