[clang] [CIR] Add support for array cleanups (PR #150499)

[Andy Kaylor via cfe-commits]

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@@ -658,10 +693,38 @@ void CIRGenFunction::emitNullabilityCheck(LValue lhs, mlir::Value rhs,
 ///   elements
 void CIRGenFunction::emitDestroy(Address addr, QualType type,
                                  Destroyer *destroyer) {
-  if (getContext().getAsArrayType(type))
-    cgm.errorNYI("emitDestroy: array type");
+  const ArrayType *arrayType = getContext().getAsArrayType(type);
+  if (!arrayType)
+    return destroyer(*this, addr, type);
+
+  mlir::Value length = emitArrayLength(arrayType, type, addr);
+
+  CharUnits elementAlign = addr.getAlignment().alignmentOfArrayElement(
+      getContext().getTypeSizeInChars(type));
+
+  // Normally we have to check whether the array is zero-length.
+  bool checkZeroLength = true;
+
+  // But if the array length is constant, we can suppress that.
+  auto constantCount = dyn_cast<cir::ConstantOp>(length.getDefiningOp());
+  if (constantCount) {
+    auto constIntAttr = mlir::dyn_cast<cir::IntAttr>(constantCount.getValue());
+    // ...and if it's constant zero, we can just skip the entire thing.
+    if (constIntAttr && constIntAttr.getUInt() == 0)
+      return;
+    checkZeroLength = false;
+  } else {
+    cgm.errorNYI("emitDestroy: variable length array");
+    return;
+  }
+
+  mlir::Value begin = addr.getPointer();
+  mlir::Value end; // This will be used for future non-constant counts.
+  emitArrayDestroy(begin, end, type, elementAlign, destroyer, checkZeroLength);
 
-  return destroyer(*this, addr, type);
+  // If the array destroy didn't use the length op, we can erase it.
+  if (constantCount.use_empty())
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andykaylor wrote:

We will probably need to switch back to the if-else structure when we support VLAs, but for now your suggestion looks better. I'll make the change.

https://github.com/llvm/llvm-project/pull/150499