The following makes sure to remap (or rather drop for simplicity)
dependence info encoded in MR_DEPENDENCE_CLIQUE when PRE PHI translation
translates a reference over a backedge since that ends up interleaving
two different loop iterations which boils down to two different
inline copies.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed to trunk.
2021-11-03 Richard Biener <rguent...@suse.de>
PR tree-optimization/102970
* tree-ssa-pre.c (phi_translate_1): Drop clique and base
when translating a MEM_REF over a backedge.
* g++.dg/opt/pr102970.C: New testcase.
---
gcc/testsuite/g++.dg/opt/pr102970.C | 60 +++++++++++++++++++++++++++++
gcc/tree-ssa-pre.c | 15 ++++++++
2 files changed, 75 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/opt/pr102970.C
diff --git a/gcc/testsuite/g++.dg/opt/pr102970.C
b/gcc/testsuite/g++.dg/opt/pr102970.C
new file mode 100644
index 00000000000..cf5b0ed70b4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr102970.C
@@ -0,0 +1,60 @@
+// { dg-do run }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O2 -funroll-loops -fno-tree-vectorize" }
+
+#include <vector>
+#include <algorithm>
+#include <cassert>
+
+struct box {
+ box(int xmin, int xmax, int ymin, int ymax) noexcept
+ : m_xmin(xmin),
+ m_xmax(xmax),
+ m_ymin(ymin),
+ m_ymax(ymax) {
+ }
+
+ box(box const & o) noexcept
+ : m_xmin(o.m_xmin),
+ m_xmax(o.m_xmax),
+ m_ymin(o.m_ymin),
+ m_ymax(o.m_ymax) { }
+
+ int m_xmin;
+ int m_xmax;
+ int m_ymin;
+ int m_ymax;
+};
+
+
+int main() {
+ std::vector<box> vRects{ // requires 18 elements
+ { 900, 11, 22, 33 },
+ { 901, 11, 22, 33 },
+ { 902, 11, 22, 33 },
+ { 903, 11, 22, 33 },
+ { 704, 11, 22, 33 },
+ { 705, 11, 22, 33 },
+ { 706, 11, 22, 33 },
+ { 707, 11, 22, 33 },
+ { 808, 11, 22, 33 },
+ { 809, 11, 22, 33 },
+ { 810, 11, 22, 33 },
+ { 811, 11, 22, 33 },
+ { 812, 11, 22, 33 },
+ { 813, 11, 22, 33 },
+ { 814, 11, 22, 33 },
+ { 815, 11, 22, 33 },
+ { 816, 11, 22, 33 },
+ { 817, 11, 22, 33 },
+ { 818, 11, 22, 33 },
+ };
+
+ std::stable_sort(vRects.begin(), vRects.end(),
+ [](auto const &r1, auto const &r2) -> bool
+ {
+ if (r2.m_xmax==0||r2.m_ymin==0||r2.m_ymax==0){__builtin_abort();}
+ return r1.m_xmin < r2.m_xmin;
+ });
+ return 0;
+}
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 1cc1aae694f..dc55d868cc1 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -1588,6 +1588,21 @@ phi_translate_1 (bitmap_set_t dest,
newoperands.release ();
return NULL;
}
+ /* When we translate a MEM_REF across a backedge and we have
+ restrict info that's not from our functions parameters
+ we have to remap it since we now may deal with a different
+ instance where the dependence info is no longer valid.
+ See PR102970. Note instead of keeping a remapping table
+ per backedge we simply throw away restrict info. */
+ if ((newop.opcode == MEM_REF
+ || newop.opcode == TARGET_MEM_REF)
+ && newop.clique > 1
+ && (e->flags & EDGE_DFS_BACK))
+ {
+ newop.clique = 0;
+ newop.base = 0;
+ changed = true;
+ }
if (!changed)
continue;
if (!newoperands.exists ())
--
2.31.1
