On July 11, 2020 10:01:41 AM GMT+02:00, Richard Sandiford
<richard.sandif...@arm.com> wrote:
>The range infrastructure has code to decompose POLY_INT_CST ranges
>to worst-case integer bounds. However, it had the fundamental flaw
>(obvious in hindsight) that it applied to anti-ranges too, meaning
>that a range 2+2X would end up with a range of ~[2, +INF], i.e.
>[-INF, 1]. This patch decays to varying in that case instead.
>
>I'm still a bit uneasy about this. ISTM that in terms of
>generality:
>
> SSA_NAME => POLY_INT_CST => INTEGER_CST
> => ADDR_EXPR
>
>I.e. an SSA_NAME could store a POLY_INT_CST and a POLY_INT_CST
>could store an INTEGER_CST (before canonicalisation). POLY_INT_CST
>is also “as constant as” ADDR_EXPR (well, OK, only some ADDR_EXPRs
>are run-time rather than link-time constants, whereas all POLY_INT_CSTs
>are, but still). So it seems like we should at least be able to treat
>POLY_INT_CST as symbolic. On the other hand, I don't have any examples
>in which that would be useful.
>
>Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK for trunk and
>GCC 10?
OK.
Thanks,
Richard.
>Richard
>
>
>gcc/
> PR tree-optimization/96146
> * value-range.cc (value_range::set): Only decompose POLY_INT_CST
> bounds to integers for VR_RANGE. Decay to VR_VARYING for anti-ranges
> involving POLY_INT_CSTs.
>
>gcc/testsuite/
> PR tree-optimization/96146
> * gcc.target/aarch64/sve/acle/general/pr96146.c: New test.
>---
> .../aarch64/sve/acle/general/pr96146.c | 20 ++++++++
> gcc/value-range.cc | 47 +++++++++++--------
> 2 files changed, 48 insertions(+), 19 deletions(-)
>create mode 100644
>gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr96146.c
>
>diff --git
>a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr96146.c
>b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr96146.c
>new file mode 100644
>index 00000000000..b05fac4918d
>--- /dev/null
>+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr96146.c
>@@ -0,0 +1,20 @@
>+/* { dg-do run { target aarch64_sve_hw } } */
>+/* { dg-options "-O3" } */
>+
>+#include <arm_sve.h>
>+
>+void __attribute__ ((noipa))
>+f (volatile int *x)
>+{
>+ int i;
>+ for (int i = 0; i < svcntd (); ++i)
>+ *x = i;
>+}
>+
>+int
>+main (void)
>+{
>+ volatile int x;
>+ f (&x);
>+ return 0;
>+}
>diff --git a/gcc/value-range.cc b/gcc/value-range.cc
>index 929a6b59aaf..bc4b061da57 100644
>--- a/gcc/value-range.cc
>+++ b/gcc/value-range.cc
>@@ -86,7 +86,34 @@ value_range::set (tree min, tree max,
>value_range_kind kind)
> set_undefined ();
> return;
> }
>- else if (kind == VR_VARYING)
>+
>+ if (kind == VR_RANGE)
>+ {
>+ /* 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;
>+ }
>+
>+ if (kind == VR_VARYING)
> {
> gcc_assert (TREE_TYPE (min) == TREE_TYPE (max));
> tree typ = TREE_TYPE (min);
>@@ -99,24 +126,6 @@ value_range::set (tree min, tree max,
>value_range_kind kind)
> return;
> }
>
>- /* 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);
>- }
>-
> /* Nothing to canonicalize for symbolic ranges. */
> if (TREE_CODE (min) != INTEGER_CST
> || TREE_CODE (max) != INTEGER_CST)
