[polly] [Polly] Restate array sizes and subscripts when the element type shrinks (PR #221496)

[Timur Baidusenov via llvm-commits]

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@@ -476,6 +514,26 @@ void MemoryAccess::updateDimensionality() {
   if (DimsAccess == 1) {
     isl::val V = isl::val(Ctx, ArrayElemSize);
     AccessRelation = AccessRelation.floordiv_val(V);
+  } else if (ElemBytes > ArrayElemSize) {
+    // A delinearized access has its subscripts in elements of the type it
+    // reads or writes, which is not the canonical element type of the array
+    // when some other access forced a smaller one. Restate the innermost
+    // subscript in canonical elements too; the outer ones count rows and are
+    // already stated in the sizes this access was delinearized against.
+    assert(ElemBytes % ArrayElemSize == 0 &&
+           "Loaded element size should be multiple of canonical element size");
+    isl::map Scale = isl::map::from_domain_and_range(
+        isl::set::universe(ArraySpace), isl::set::universe(ArraySpace));
+    for (auto i : seq<unsigned>(0, DimsArray - 1))
+      Scale = Scale.equate(isl::dim::in, i, isl::dim::out, i);
+
+    isl::local_space LS(Scale.get_space());
+    isl::constraint C = isl::constraint::alloc_equality(LS);
+    C = C.set_coefficient_si(isl::dim::in, DimsArray - 1,
+                             ElemBytes / ArrayElemSize);
+    C = C.set_coefficient_si(isl::dim::out, DimsArray - 1, -1);
+    Scale = Scale.add_constraint(C);
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bai-tim wrote:

Done

https://github.com/llvm/llvm-project/pull/221496