[LoopUtils] Updated deleteDeadLoop() to handle loop nest.

Reviewer: kariddi, sanjoy, reames, Meinersbur, bmahjour, etiotto,
kbarton
Reviewed By: Meinersbur
Subscribers: mgorny, hiraditya, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D70939

llvm/unittests/Transforms/Utils/LoopUtilsTest.cpp

@@ -0,0 +1,90 @@
+//===- LoopUtilsTest.cpp - Unit tests for LoopUtils -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/LoopUtils.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
+  if (!Mod)
+    Err.print("LoopUtilsTests", errs());
+  return Mod;
+}
+
+static void run(Module &M, StringRef FuncName,
+                function_ref<void(Function &F, DominatorTree &DT,
+                                  ScalarEvolution &SE, LoopInfo &LI)>
+                    Test) {
+  Function *F = M.getFunction(FuncName);
+  DominatorTree DT(*F);
+  TargetLibraryInfoImpl TLII;
+  TargetLibraryInfo TLI(TLII);
+  AssumptionCache AC(*F);
+  LoopInfo LI(DT);
+  ScalarEvolution SE(*F, TLI, AC, DT, LI);
+  Test(*F, DT, SE, LI);
+}
+
+TEST(LoopUtils, DeleteDeadLoopNest) {
+  LLVMContext C;
+  std::unique_ptr<Module> M =
+      parseIR(C, "define void @foo() {\n"
+                 "entry:\n"
+                 "  br label %for.i\n"
+                 "for.i:\n"
+                 "  %i = phi i64 [ 0, %entry ], [ %inc.i, %for.i.latch ]\n"
+                 "  br label %for.j\n"
+                 "for.j:\n"
+                 "  %j = phi i64 [ 0, %for.i ], [ %inc.j, %for.j ]\n"
+                 "  %inc.j = add nsw i64 %j, 1\n"
+                 "  %cmp.j = icmp slt i64 %inc.j, 100\n"
+                 "  br i1 %cmp.j, label %for.j, label %for.k.preheader\n"
+                 "for.k.preheader:\n"
+                 "  br label %for.k\n"
+                 "for.k:\n"
+                 "  %k = phi i64 [ %inc.k, %for.k ], [ 0, %for.k.preheader ]\n"
+                 "  %inc.k = add nsw i64 %k, 1\n"
+                 "  %cmp.k = icmp slt i64 %inc.k, 100\n"
+                 "  br i1 %cmp.k, label %for.k, label %for.i.latch\n"
+                 "for.i.latch:\n"
+                 "  %inc.i = add nsw i64 %i, 1\n"
+                 "  %cmp.i = icmp slt i64 %inc.i, 100\n"
+                 "  br i1 %cmp.i, label %for.i, label %for.end\n"
+                 "for.end:\n"
+                 "  ret void\n"
+                 "}\n");
+
+  run(*M, "foo",
+      [&](Function &F, DominatorTree &DT, ScalarEvolution &SE, LoopInfo &LI) {
+        assert(LI.begin() != LI.end() && "Expecting loops in function F");
+        Loop *L = *LI.begin();
+        assert(L && L->getName() == "for.i" && "Expecting loop for.i");
+
+        deleteDeadLoop(L, &DT, &SE, &LI);
+
+        assert(DT.verify(DominatorTree::VerificationLevel::Fast) &&
+               "Expecting valid dominator tree");
+        LI.verify(DT);
+        assert(LI.begin() == LI.end() &&
+               "Expecting no loops left in function F");
+        SE.verify();
+
+        Function::iterator FI = F.begin();
+        BasicBlock *Entry = &*(FI++);
+        assert(Entry->getName() == "entry" && "Expecting BasicBlock entry");
+        const BranchInst *BI = dyn_cast<BranchInst>(Entry->getTerminator());
+        assert(BI && "Expecting valid branch instruction");
+        EXPECT_EQ(BI->getNumSuccessors(), (unsigned)1);
+        EXPECT_EQ(BI->getSuccessor(0)->getName(), "for.end");
+      });
+}