Merge pull request #13207 from MathiasVP/use-equiv-class-in-getInstruction

C++: Reduce memory pressure from `getInstruction`

Author: Robert Marsh

cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll

@@ -255,14 +255,28 @@ private module Cached {
   cached
   newtype TIRBlock = MkIRBlock(Instruction firstInstr) { startsBasicBlock(firstInstr) }
 
-  /** Holds if `i` is the `index`th instruction the block starting with `first`. */
-  private Instruction getInstructionFromFirst(Instruction first, int index) =
-    shortestDistances(startsBasicBlock/1, adjacentInBlock/2)(first, result, index)
+  /** Gets the index of `i` in its `IRBlock`. */
+  private int getMemberIndex(Instruction i) {
+    startsBasicBlock(i) and
+    result = 0
+    or
+    exists(Instruction iPrev |
+      adjacentInBlock(iPrev, i) and
+      result = getMemberIndex(iPrev) + 1
+    )
+  }
+
+  private module BlockAdjacency = QlBuiltins::EquivalenceRelation<Instruction, adjacentInBlock/2>;
 
   /** Holds if `i` is the `index`th instruction in `block`. */
   cached
   Instruction getInstruction(TIRBlock block, int index) {
-    result = getInstructionFromFirst(getFirstInstruction(block), index)
+    exists(Instruction first | block = MkIRBlock(first) |
+      first = result and index = 0
+      or
+      index = getMemberIndex(result) and
+      BlockAdjacency::getEquivalenceClass(first) = BlockAdjacency::getEquivalenceClass(result)
+    )
   }
 
   cached

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/IRBlock.qll

@@ -255,14 +255,28 @@ private module Cached {
   cached
   newtype TIRBlock = MkIRBlock(Instruction firstInstr) { startsBasicBlock(firstInstr) }
 
-  /** Holds if `i` is the `index`th instruction the block starting with `first`. */
-  private Instruction getInstructionFromFirst(Instruction first, int index) =
-    shortestDistances(startsBasicBlock/1, adjacentInBlock/2)(first, result, index)
+  /** Gets the index of `i` in its `IRBlock`. */
+  private int getMemberIndex(Instruction i) {
+    startsBasicBlock(i) and
+    result = 0
+    or
+    exists(Instruction iPrev |
+      adjacentInBlock(iPrev, i) and
+      result = getMemberIndex(iPrev) + 1
+    )
+  }
+
+  private module BlockAdjacency = QlBuiltins::EquivalenceRelation<Instruction, adjacentInBlock/2>;
 
   /** Holds if `i` is the `index`th instruction in `block`. */
   cached
   Instruction getInstruction(TIRBlock block, int index) {
-    result = getInstructionFromFirst(getFirstInstruction(block), index)
+    exists(Instruction first | block = MkIRBlock(first) |
+      first = result and index = 0
+      or
+      index = getMemberIndex(result) and
+      BlockAdjacency::getEquivalenceClass(first) = BlockAdjacency::getEquivalenceClass(result)
+    )
   }
 
   cached

cpp/ql/lib/semmle/code/cpp/ir/implementation/unaliased_ssa/IRBlock.qll

@@ -255,14 +255,28 @@ private module Cached {
   cached
   newtype TIRBlock = MkIRBlock(Instruction firstInstr) { startsBasicBlock(firstInstr) }
 
-  /** Holds if `i` is the `index`th instruction the block starting with `first`. */
-  private Instruction getInstructionFromFirst(Instruction first, int index) =
-    shortestDistances(startsBasicBlock/1, adjacentInBlock/2)(first, result, index)
+  /** Gets the index of `i` in its `IRBlock`. */
+  private int getMemberIndex(Instruction i) {
+    startsBasicBlock(i) and
+    result = 0
+    or
+    exists(Instruction iPrev |
+      adjacentInBlock(iPrev, i) and
+      result = getMemberIndex(iPrev) + 1
+    )
+  }
+
+  private module BlockAdjacency = QlBuiltins::EquivalenceRelation<Instruction, adjacentInBlock/2>;
 
   /** Holds if `i` is the `index`th instruction in `block`. */
   cached
   Instruction getInstruction(TIRBlock block, int index) {
-    result = getInstructionFromFirst(getFirstInstruction(block), index)
+    exists(Instruction first | block = MkIRBlock(first) |
+      first = result and index = 0
+      or
+      index = getMemberIndex(result) and
+      BlockAdjacency::getEquivalenceClass(first) = BlockAdjacency::getEquivalenceClass(result)
+    )
   }
 
   cached

csharp/ql/src/experimental/ir/implementation/raw/IRBlock.qll

@@ -255,14 +255,28 @@ private module Cached {
   cached
   newtype TIRBlock = MkIRBlock(Instruction firstInstr) { startsBasicBlock(firstInstr) }
 
-  /** Holds if `i` is the `index`th instruction the block starting with `first`. */
-  private Instruction getInstructionFromFirst(Instruction first, int index) =
-    shortestDistances(startsBasicBlock/1, adjacentInBlock/2)(first, result, index)
+  /** Gets the index of `i` in its `IRBlock`. */
+  private int getMemberIndex(Instruction i) {
+    startsBasicBlock(i) and
+    result = 0
+    or
+    exists(Instruction iPrev |
+      adjacentInBlock(iPrev, i) and
+      result = getMemberIndex(iPrev) + 1
+    )
+  }
+
+  private module BlockAdjacency = QlBuiltins::EquivalenceRelation<Instruction, adjacentInBlock/2>;
 
   /** Holds if `i` is the `index`th instruction in `block`. */
   cached
   Instruction getInstruction(TIRBlock block, int index) {
-    result = getInstructionFromFirst(getFirstInstruction(block), index)
+    exists(Instruction first | block = MkIRBlock(first) |
+      first = result and index = 0
+      or
+      index = getMemberIndex(result) and
+      BlockAdjacency::getEquivalenceClass(first) = BlockAdjacency::getEquivalenceClass(result)
+    )
   }
 
   cached

csharp/ql/src/experimental/ir/implementation/unaliased_ssa/IRBlock.qll

@@ -255,14 +255,28 @@ private module Cached {
   cached
   newtype TIRBlock = MkIRBlock(Instruction firstInstr) { startsBasicBlock(firstInstr) }
 
-  /** Holds if `i` is the `index`th instruction the block starting with `first`. */
-  private Instruction getInstructionFromFirst(Instruction first, int index) =
-    shortestDistances(startsBasicBlock/1, adjacentInBlock/2)(first, result, index)
+  /** Gets the index of `i` in its `IRBlock`. */
+  private int getMemberIndex(Instruction i) {
+    startsBasicBlock(i) and
+    result = 0
+    or
+    exists(Instruction iPrev |
+      adjacentInBlock(iPrev, i) and
+      result = getMemberIndex(iPrev) + 1
+    )
+  }
+
+  private module BlockAdjacency = QlBuiltins::EquivalenceRelation<Instruction, adjacentInBlock/2>;
 
   /** Holds if `i` is the `index`th instruction in `block`. */
   cached
   Instruction getInstruction(TIRBlock block, int index) {
-    result = getInstructionFromFirst(getFirstInstruction(block), index)
+    exists(Instruction first | block = MkIRBlock(first) |
+      first = result and index = 0
+      or
+      index = getMemberIndex(result) and
+      BlockAdjacency::getEquivalenceClass(first) = BlockAdjacency::getEquivalenceClass(result)
+    )
   }
 
   cached