[Mlir-commits] [mlir] [MLIR][Mem2Reg][LLVM] Enhance partial load support (PR #89094)

[Tobias Gysi]

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@@ -122,37 +123,119 @@ bool LLVM::StoreOp::storesTo(const MemorySlot &slot) {
   return getAddr() == slot.ptr;
 }
 
-/// Checks that two types are the same or can be cast into one another.
-static bool areCastCompatible(const DataLayout &layout, Type lhs, Type rhs) {
-  return lhs == rhs || (!isa<LLVM::LLVMStructType, LLVM::LLVMArrayType>(lhs) &&
-                        !isa<LLVM::LLVMStructType, LLVM::LLVMArrayType>(rhs) &&
-                        layout.getTypeSize(lhs) == layout.getTypeSize(rhs));
+/// Checks if `type` can be used in any kind of conversion sequences.
+static bool isSupportedTypeForConversion(Type type) {
+  // Aggregate types are not bitcastable.
+  if (isa<LLVM::LLVMStructType, LLVM::LLVMArrayType>(type))
+    return false;
+
+  // LLVM vector types are only used for either pointers or target specific
+  // types. These types cannot be casted in the general case, thus the memory
+  // optimizations do not support them.
+  if (isa<LLVM::LLVMFixedVectorType, LLVM::LLVMScalableVectorType>(type))
+    return false;
+
+  // Scalable types are not supported.
+  if (auto vectorType = dyn_cast<VectorType>(type))
+    return !vectorType.isScalable();
+  return true;
 }
 
+/// Checks that `rhs` can be converted to `lhs` by a sequence of casts and
+/// truncations.
+static bool areConversionCompatible(const DataLayout &layout, Type lhs,
+                                    Type rhs) {
+  if (lhs == rhs)
+    return true;
+
+  if (!isSupportedTypeForConversion(lhs) || !isSupportedTypeForConversion(rhs))
+    return false;
+
+  // Pointer casts will only be sane when the bitsize of both pointer types is
+  // the same.
+  if (isa<LLVM::LLVMPointerType>(lhs) && isa<LLVM::LLVMPointerType>(rhs))
+    return layout.getTypeSize(lhs) == layout.getTypeSize(rhs);
+
+  return layout.getTypeSize(lhs) <= layout.getTypeSize(rhs);
+}
+
+/// Checks if `dataLayout` describes a little endian layout.
+static bool isLittleEndian(const DataLayout &dataLayout) {
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gysit wrote:

I would probably change to isBigEndian and invert the logic since this is corner case. Then the check for !endiannessStr is not needed.

https://github.com/llvm/llvm-project/pull/89094