The dominance computation already has logic for computing if an edge dominates

a use or a BB, but it is inline in the handling of the invoke instruction.

This patch refactors it so that it can be used in other cases. For example, in

define i32 @f(i32 %x) {
bb0:
  %cmp = icmp eq i32 %x, 0
  br i1 %cmp, label %bb2, label %bb1
bb1:
  br label %bb2
bb2:
  %cond = phi i32 [ %x, %bb0 ], [ 0, %bb1 ]
  %foo = add i32 %cond, %x
  ret i32 %foo
}

GVN should be able to replace %x with 0 in any use that is dominated by the
true edge out of bb0. In the above example the only such use is the one in
the phi.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161429 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/Analysis/Dominators.h b/include/llvm/Analysis/Dominators.h
index 45be59b974..25fb363ad4 100644
--- a/include/llvm/Analysis/Dominators.h
+++ b/include/llvm/Analysis/Dominators.h
@@ -705,6 +705,20 @@ DominatorTreeBase<NodeT>::properlyDominates(const NodeT *A, const NodeT *B) {
 
 EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<BasicBlock>);
 
+class BasicBlockEdge {
+  const BasicBlock *Start;
+  const BasicBlock *End;
+public:
+  BasicBlockEdge(const BasicBlock *Start_, const BasicBlock *End_) :
+    Start(Start_), End(End_) { }
+  const BasicBlock *getStart() const {
+    return Start;
+  }
+  const BasicBlock *getEnd() const {
+    return End;
+  }
+};
+
 //===-------------------------------------
 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
 /// compute a normal dominator tree.
@@ -778,6 +792,8 @@ public:
   bool dominates(const Instruction *Def, const Use &U) const;
   bool dominates(const Instruction *Def, const Instruction *User) const;
   bool dominates(const Instruction *Def, const BasicBlock *BB) const;
+  bool dominates(const BasicBlockEdge &BBE, const Use &U) const;
+  bool dominates(const BasicBlockEdge &BBE, const BasicBlock *BB) const;
 
   bool properlyDominates(const DomTreeNode *A, const DomTreeNode *B) const {
     return DT->properlyDominates(A, B);