[llvm] [SandboxIR][Tracker] Track eraseFromParent() (PR #99431)

[via llvm-commits]

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@@ -99,6 +100,46 @@ class UseSet : public IRChangeBase {
 #endif
 };
 
+class EraseFromParent : public IRChangeBase {
+  /// Contains all the data we need to restore an "erased" (i.e., detached)
+  /// instruction: the instruction itself and the operands data.
+  struct InstrData {
+    /// The operand and the corresponding operand number.
+    struct OpData {
+      llvm::Value *Op;
+      unsigned OpNum;
+    };
+    /// The operands that got dropped.
+    SmallVector<OpData> OpDataVec;
+    /// The instruction that got "erased".
+    llvm::Instruction *LLVMI;
+  };
+  /// The instruction data is in reverse program order, which helps create the
+  /// original program order during revert().
+  SmallVector<InstrData> InstrData;
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vporpo wrote:

OK we can a new context class, like `class TestContext : public Context` that can match a multi-instruction pattern like for example a 2-instruction sequence of a `sub` followed by an `add`. Then in the tests we need to test multi-instructions we can use that `TestContext` instead of the standard `Context`.

Yeah that would have to be a separate PR. I am pretty sure there is a lot of missing functionality in the SandboxIR API that would need fixing and more testing too once we introduce multi-instructions.

https://github.com/llvm/llvm-project/pull/99431