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

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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
This commit is contained in:
Rafael Espindola
2012-08-07 17:30:46 +00:00
parent 8da94ad6e0
commit 702bcce747
2 changed files with 57 additions and 28 deletions
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16
include/llvm/Analysis/Dominators.h
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@ -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);