This is a gcc-10 version of:
Richard Sandiford <richard.sandif...@arm.com> writes:
> This PR shows another problem with calculating value ranges for
> POLY_INT_CSTs. We have:
>
> ivtmp_76 = ASSERT_EXPR <ivtmp_60, ivtmp_60 > POLY_INT_CST [9, 4294967294]>
>
> where the VQ coefficient is unsigned but is effectively acting
> as a negative number. We wrongly give the POLY_INT_CST the range:
>
> [9, INT_MAX]
>
> and things go downhill from there: later iterations of the unrolled
> epilogue are wrongly removed as dead.
>
> I guess this is the final nail in the coffin for doing VRP on
> POLY_INT_CSTs. For other similarly exotic testcases we could have
> overflow for any coefficient, not just those that could be treated
> as contextually negative.
>
> Testing TYPE_OVERFLOW_UNDEFINED doesn't seem like an option because we
> couldn't handle warn_strict_overflow properly. At this stage we're
> just recording a range that might or might not lead to strict-overflow
> assumptions later.
>
> It still feels like we should be able to do something here, but for
> now removing the code seems safest. It's also telling that there
> are no testsuite failures on SVE from doing this.
>
> Tested on aarch64-linux-gnu (with and without SVE) and
> x86_64-linux-gnu. OK for trunk and backports?
>
> Richard
The backport ended up looking a bit different. Rather than fall through
to the later VR_VARYING code (which asserts for certain min and max values),
this code just moves directly to varying.
Tested on aarch64-linux-gnu, aarch64_be-elf, arm-linux-gnueabihf,
armeb-elf and x86_64-linux-gnu. OK for GCC 10?
Richard
gcc/
PR tree-optimization/97457
* value-range.cc (irange::set): Don't decay POLY_INT_CST ranges
to integer ranges.
gcc/testsuite/
PR tree-optimization/97457
* gcc.dg/vect/pr97457.c: New test.
(cherry picked from commit 54ef7701a9dec8c923a12d1983f8a051ba88a7b9)
---
gcc/testsuite/gcc.dg/vect/pr97457.c | 15 +++++++++++++++
gcc/value-range.cc | 29 ++++++-----------------------
2 files changed, 21 insertions(+), 23 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/pr97457.c
diff --git a/gcc/testsuite/gcc.dg/vect/pr97457.c
b/gcc/testsuite/gcc.dg/vect/pr97457.c
new file mode 100644
index 00000000000..506ba249b00
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr97457.c
@@ -0,0 +1,15 @@
+/* { dg-additional-options "-O3" } */
+
+int a;
+long c;
+signed char d(char e, char f) { return e + f; }
+int main(void) {
+ for (; a <= 1; a++) {
+ c = -8;
+ for (; c != 3; c = d(c, 1))
+ ;
+ }
+ char b = c;
+ if (b != 3)
+ __builtin_abort();
+}
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index bc4b061da57..04820846fe0 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -87,30 +87,13 @@ value_range::set (tree min, tree max, value_range_kind kind)
return;
}
- if (kind == VR_RANGE)
+ if (kind != VR_VARYING
+ && (POLY_INT_CST_P (min) || POLY_INT_CST_P (max)))
{
- /* Convert POLY_INT_CST bounds into worst-case INTEGER_CST bounds. */
- if (POLY_INT_CST_P (min))
- {
- tree type_min = vrp_val_min (TREE_TYPE (min));
- widest_int lb
- = constant_lower_bound_with_limit (wi::to_poly_widest (min),
- wi::to_widest (type_min));
- min = wide_int_to_tree (TREE_TYPE (min), lb);
- }
- if (POLY_INT_CST_P (max))
- {
- tree type_max = vrp_val_max (TREE_TYPE (max));
- widest_int ub
- = constant_upper_bound_with_limit (wi::to_poly_widest (max),
- wi::to_widest (type_max));
- max = wide_int_to_tree (TREE_TYPE (max), ub);
- }
- }
- else if (kind != VR_VARYING)
- {
- if (POLY_INT_CST_P (min) || POLY_INT_CST_P (max))
- kind = VR_VARYING;
+ tree typ = TREE_TYPE (min);
+ gcc_checking_assert (useless_type_conversion_p (typ, TREE_TYPE (max)));
+ set_varying (typ);
+ return;
}
if (kind == VR_VARYING)
