[GCC,12] tree-optimization/113896 - reduction of permuted external vector
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Commit Message
The following fixes eliding of the permutation of a BB reduction
of an existing vector which breaks materialization of live lanes
as we fail to permute the SLP_TREE_SCALAR_STMTS vector.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/113896
* tree-vect-slp.cc (vect_optimize_slp): Permute
SLP_TREE_SCALAR_STMTS when eliding a permuation in a
VEC_PERM node we need to preserve because it wraps an
extern vector.
* g++.dg/torture/pr113896.C: New testcase.
---
gcc/testsuite/g++.dg/torture/pr113896.C | 35 +++++++++++++++++++++++++
gcc/tree-vect-slp.cc | 9 +++++++
2 files changed, 44 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/torture/pr113896.C
new file mode 100644
@@ -0,0 +1,35 @@
+// { dg-do run }
+// { dg-additional-options "-ffast-math" }
+
+double a1 = 1.0;
+double a2 = 1.0;
+
+void __attribute__((noipa))
+f(double K[2], bool b)
+{
+ double A[] = {
+ b ? a1 : a2,
+ 0,
+ 0,
+ 0
+ };
+
+ double sum{};
+ for(double a : A) sum += a;
+ for(double& a : A) a /= sum;
+
+ if (b) {
+ K[0] = A[0]; // 1.0
+ K[1] = A[1]; // 0.0
+ } else {
+ K[0] = A[0] + A[1];
+ }
+}
+
+int main()
+{
+ double K[2]{};
+ f(K, true);
+ if (K[0] != 1. || K[1] != 0.)
+ __builtin_abort ();
+}
@@ -4058,6 +4058,15 @@ vect_optimize_slp (vec_info *vinfo)
{
/* Preserve the special VEC_PERM we use to shield existing
vector defs from the rest. But make it a no-op. */
+ auto_vec<stmt_vec_info, 64> saved;
+ saved.create (SLP_TREE_SCALAR_STMTS (old).length ());
+ for (unsigned i = 0;
+ i < SLP_TREE_SCALAR_STMTS (old).length (); ++i)
+ saved.quick_push (SLP_TREE_SCALAR_STMTS (old)[i]);
+ for (unsigned i = 0;
+ i < SLP_TREE_SCALAR_STMTS (old).length (); ++i)
+ SLP_TREE_SCALAR_STMTS (old)[i]
+ = saved[SLP_TREE_LANE_PERMUTATION (old)[i].second];
unsigned i = 0;
for (std::pair<unsigned, unsigned> &p
: SLP_TREE_LANE_PERMUTATION (old))