[llvm] [FunctionAttrs] Add the "initializes" attribute inference (PR #97373)

[Haopeng Liu via llvm-commits]

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@@ -580,6 +582,206 @@ struct ArgumentUsesTracker : public CaptureTracker {
   const SCCNodeSet &SCCNodes;
 };
 
+// A struct of argument use: a Use and the offset it accesses. This struct
+// is to track uses inside function via GEP. If GEP has a non-constant index,
+// the Offset field is nullopt.
+struct ArgumentUse {
+  Use *U;
+  std::optional<int64_t> Offset;
+};
+
+// A struct of argument access info. "Unknown" accesses are the cases like
+// unrecognized instructions, instructions that have more than one use of
+// the argument, or volatile memory accesses. "Unknown" implies "IsClobber"
+// and an empty access range.
+// Write or Read accesses can be clobbers as well for example, a Load with
+// scalable type.
+struct ArgumentAccessInfo {
+  enum class AccessType : uint8_t { Write, Read, Unknown };
+  AccessType ArgAccessType;
+  bool IsClobber = false;
+  ConstantRangeList AccessRanges;
+};
+
+// A struct to wrap the argument use info per block.
+struct UsesPerBlockInfo {
+  SmallDenseMap<Instruction *, ArgumentAccessInfo, 4> Insts;
+  bool HasWrites = false;
+  bool HasClobber = false;
+};
+
+// A struct to summarize the argument use info in a function.
+struct ArgumentUsesSummary {
+  bool HasAnyWrite = false;
+  bool HasWriteOutsideEntryBB = false;
+  SmallDenseMap<const BasicBlock *, UsesPerBlockInfo, 16> UsesPerBlock;
+};
+
+ArgumentAccessInfo GetArgmentAccessInfo(const Instruction *I,
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haopliu wrote:

Done.

https://github.com/llvm/llvm-project/pull/97373