C++: Remove VariableGroup

It's empty in the unaliased SSA, and the aliased SSA has been removed.

Author: igfoo

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImplCommon.qll

@@ -40,8 +40,7 @@ predicate ignoreInstruction(Instruction instr) {
     instr instanceof AliasedDefinitionInstruction or
     instr instanceof AliasedUseInstruction or
     instr instanceof InitializeNonLocalInstruction or
-    instr instanceof ReturnIndirectionInstruction or
-    instr instanceof UninitializedGroupInstruction
+    instr instanceof ReturnIndirectionInstruction
   )
 }
 

cpp/ql/lib/semmle/code/cpp/ir/implementation/Opcode.qll

@@ -1250,17 +1250,6 @@ module Opcode {
     }
   }
 
-  /**
-   * The `Opcode` for a `UninitializedGroup`.
-   *
-   * See the `UninitializedGroupInstruction` documentation for more details.
-   */
-  class UninitializedGroup extends Opcode, TUninitializedGroup {
-    final override string toString() { result = "UninitializedGroup" }
-
-    override GroupedMemoryAccess getWriteMemoryAccess() { any() }
-  }
-
   /**
    * The `Opcode` for an `InlineAsmInstruction`.
    *

cpp/ql/lib/semmle/code/cpp/ir/implementation/internal/TInstruction.qll

@@ -30,8 +30,7 @@ newtype TInstruction =
   TUnaliasedSsaChiInstruction(TRawInstruction primaryInstruction) { none() } or
   TUnaliasedSsaUnreachedInstruction(IRFunctionBase irFunc) {
     UnaliasedSsa::Ssa::hasUnreachedInstruction(irFunc)
-  } or
-  TUnaliasedSsaUninitializedGroupInstruction(UnaliasedSsa::Ssa::VariableGroup vg)
+  }
 
 /**
  * Provides wrappers for the constructors of each branch of `TInstruction` that is used by the
@@ -52,11 +51,7 @@ module UnaliasedSsaInstructions {
 
   class TChiInstruction = TUnaliasedSsaChiInstruction;
 
-  class TUninitializedGroupInstruction = TUnaliasedSsaUninitializedGroupInstruction;
-
-  class TRawOrUninitializedGroupInstruction = TRawInstruction or TUninitializedGroupInstruction;
-
-  TChiInstruction chiInstruction(TRawOrUninitializedGroupInstruction primaryInstruction) {
+  TChiInstruction chiInstruction(TRawInstruction primaryInstruction) {
     result = TUnaliasedSsaChiInstruction(primaryInstruction)
   }
 
@@ -65,10 +60,4 @@ module UnaliasedSsaInstructions {
   TUnreachedInstruction unreachedInstruction(IRFunctionBase irFunc) {
     result = TUnaliasedSsaUnreachedInstruction(irFunc)
   }
-
-  class VariableGroup = UnaliasedSsa::Ssa::VariableGroup;
-
-  // This really should just be `TUnaliasedSsaUninitializedGroupInstruction`, but that makes the
-  // compiler realize that certain expressions in `SSAConstruction` are unsatisfiable.
-  TRawOrUninitializedGroupInstruction uninitializedGroup(VariableGroup vg) { none() }
 }

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

@@ -2169,47 +2169,6 @@ class ChiInstruction extends Instruction {
   final predicate isPartialUpdate() { Construction::chiOnlyPartiallyUpdatesLocation(this) }
 }
 
-/**
- * An instruction that initializes a set of allocations that are each assigned
- * the same "virtual variable".
- *
- * As an example, consider the following snippet:
- * ```
- * int a;
- * int b;
- * int* p;
- * if(b) {
- *   p = &a;
- * } else {
- *   p = &b;
- * }
- * *p = 5;
- * int x = a;
- * ```
- *
- * Since both the address of `a` and `b` reach `p` at `*p = 5` the IR alias
- * analysis will create a region that contains both `a` and `b`. The region
- * containing both `a` and `b` are initialized by an `UninitializedGroup`
- * instruction in the entry block of the enclosing function.
- */
-class UninitializedGroupInstruction extends Instruction {
-  UninitializedGroupInstruction() { this.getOpcode() instanceof Opcode::UninitializedGroup }
-
-  /**
-   * Gets an `IRVariable` whose memory is initialized by this instruction, if any.
-   * Note: Allocations that are not represented as `IRVariable`s (such as
-   * dynamic allocations) are not returned by this predicate even if this
-   * instruction initializes such memory.
-   */
-  final IRVariable getAnIRVariable() {
-    result = Construction::getAnUninitializedGroupVariable(this)
-  }
-
-  final override string getImmediateString() {
-    result = strictconcat(this.getAnIRVariable().toString(), ",")
-  }
-}
-
 /**
  * An instruction representing unreachable code.
  *

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/IRConstruction.qll

@@ -426,8 +426,6 @@ predicate hasUnreachedInstruction(IRFunction func) {
   )
 }
 
-IRVariable getAnUninitializedGroupVariable(UninitializedGroupInstruction instr) { none() }
-
 import CachedForDebugging
 
 cached

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

@@ -2169,47 +2169,6 @@ class ChiInstruction extends Instruction {
   final predicate isPartialUpdate() { Construction::chiOnlyPartiallyUpdatesLocation(this) }
 }
 
-/**
- * An instruction that initializes a set of allocations that are each assigned
- * the same "virtual variable".
- *
- * As an example, consider the following snippet:
- * ```
- * int a;
- * int b;
- * int* p;
- * if(b) {
- *   p = &a;
- * } else {
- *   p = &b;
- * }
- * *p = 5;
- * int x = a;
- * ```
- *
- * Since both the address of `a` and `b` reach `p` at `*p = 5` the IR alias
- * analysis will create a region that contains both `a` and `b`. The region
- * containing both `a` and `b` are initialized by an `UninitializedGroup`
- * instruction in the entry block of the enclosing function.
- */
-class UninitializedGroupInstruction extends Instruction {
-  UninitializedGroupInstruction() { this.getOpcode() instanceof Opcode::UninitializedGroup }
-
-  /**
-   * Gets an `IRVariable` whose memory is initialized by this instruction, if any.
-   * Note: Allocations that are not represented as `IRVariable`s (such as
-   * dynamic allocations) are not returned by this predicate even if this
-   * instruction initializes such memory.
-   */
-  final IRVariable getAnIRVariable() {
-    result = Construction::getAnUninitializedGroupVariable(this)
-  }
-
-  final override string getImmediateString() {
-    result = strictconcat(this.getAnIRVariable().toString(), ",")
-  }
-}
-
 /**
  * An instruction representing unreachable code.
  *