[llvm] Port Swift's merge function pass to llvm: merging functions that differ in constants (PR #68235)

[Manman Ren via llvm-commits]

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+//===- FunctionComparatorIgnoringConst.h - Function Comparator --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the FunctionComparatorIgnoringConst class which is used by
+// the MergeFuncIgnoringConst pass for comparing functions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_FUNCTIONCOMPARATORIGNORINGCONST_H
+#define LLVM_TRANSFORMS_UTILS_FUNCTIONCOMPARATORIGNORINGCONST_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/Attributes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/ValueMap.h"
+#include "llvm/Support/AtomicOrdering.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Transforms/Utils/FunctionComparator.h"
+#include <set>
+
+namespace llvm {
+
+/// FunctionComparatorIgnoringConst - Compares two functions to determine
+/// whether or not they will generate machine code with the same behavior.
+class FunctionComparatorIgnoringConst : public FunctionComparator {
+public:
+  FunctionComparatorIgnoringConst(const Function *F1, const Function *F2,
+                                  GlobalNumberState *GN)
+      : FunctionComparator(F1, F2, GN) {}
+
+  int cmpOperandsIgnoringConsts(const Instruction *L, const Instruction *R,
+                                unsigned opIdx);
+
+  int cmpBasicBlocksIgnoringConsts(
+      const BasicBlock *BBL, const BasicBlock *BBR,
+      const std::set<std::pair<int, int>> *InstOpndIndex = nullptr);
+
+  int compareIgnoringConsts(
+      const std::set<std::pair<int, int>> *InstOpndIndex = nullptr);
+
+  int compareConstants(const Constant *L, const Constant *R) const {
+    return cmpConstants(L, R);
+  }
+
+private:
+  // Scratch index for instruction in order during cmpOperandsIgnoringConsts.
+  int index = 0;
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manman-ren wrote:

Done in the followup patch.

https://github.com/llvm/llvm-project/pull/68235