[Mlir-commits] [mlir] [mlir][memref] Fix mem2reg crash on zero-extent alloca (PR #216851)

[Jianhui Li]

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@@ -103,15 +103,21 @@ SmallVector<MemorySlot> memref::AllocaOp::getPromotableSlots() {
   // is only ever accessed as a whole buffer (e.g. through whole-buffer
   // `vector.transfer_read`/`vector.transfer_write`).
   if (VectorType::isValidElementType(type.getElementType())) {
+    // Vector types require strictly positive extents, so a memref with a zero
+    // extent has nothing to promote.
+    if (llvm::is_contained(type.getShape(), 0))
+      return {};
+
     // Static shape: a fixed-size vector of the same extents.
     if (type.hasStaticShape())
       return {MemorySlot{getResult(), VectorType::get(type.getShape(),
                                                       type.getElementType())}};
 
     // A 1-D memref whose single dynamic extent is `vector.vscale * C` maps to a
-    // scalable `vector<[C]x...>` slot.
+    // scalable `vector<[C]x...>` slot, for a strictly positive `C`.
     if (type.getRank() == 1 && type.isDynamicDim(0)) {
-      if (std::optional<int64_t> c = matchVScaleMultiple(getDynamicSizes()[0]))
+      if (std::optional<int64_t> c = matchVScaleMultiple(getDynamicSizes()[0]);
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Jianhui-Li wrote:

nit: consider a more meaningful name for "c", like "multiple". 

https://github.com/llvm/llvm-project/pull/216851