[Dominators] Use Instruction::comesBefore for block-local queries, NFC
Use the lazy instruction ordering facility for block-local dominance
queries.
Differential Revision: https://reviews.llvm.org/D74931
diff --git a/llvm/unittests/IR/DominatorTreeTest.cpp b/llvm/unittests/IR/DominatorTreeTest.cpp
index 7773856..22d2003 100644
--- a/llvm/unittests/IR/DominatorTreeTest.cpp
+++ b/llvm/unittests/IR/DominatorTreeTest.cpp
@@ -43,6 +43,37 @@
return M;
}
+TEST(DominatorTree, PHIs) {
+ StringRef ModuleString = R"(
+ define void @f() {
+ bb1:
+ br label %bb1
+ bb2:
+ %a = phi i32 [0, %bb1], [1, %bb2]
+ %b = phi i32 [2, %bb1], [%a, %bb2]
+ br label %bb2
+ };
+ )";
+
+ // Parse the module.
+ LLVMContext Context;
+ std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
+
+ runWithDomTree(*M, "f",
+ [&](Function &F, DominatorTree *DT, PostDominatorTree *PDT) {
+ auto FI = F.begin();
+ ++FI;
+ BasicBlock *BB2 = &*FI;
+ auto BI = BB2->begin();
+ Instruction *PhiA = &*BI++;
+ Instruction *PhiB = &*BI;
+
+ // Phis are thought to execute "instantly, together".
+ EXPECT_TRUE(DT->dominates(PhiA, PhiB));
+ EXPECT_TRUE(DT->dominates(PhiB, PhiA));
+ });
+}
+
TEST(DominatorTree, Unreachable) {
StringRef ModuleString =
"declare i32 @g()\n"