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0ac56aa46f
This PR implements the function splitBasicBlockBefore to address an
issue
that occurred during SplitEdge(BB, Succ, ...), inside splitBlockBefore.
The issue occurs in SplitEdge when the Succ has a single predecessor
and the edge between the BB and Succ is not critical. This produces
the result ‘BB->Succ->New’. The new function splitBasicBlockBefore
was added to splitBlockBefore to handle the issue and now produces
the correct result ‘BB->New->Succ’.
Below is an example of splitting the block bb1 at its first instruction.
/// Original IR
bb0:
br bb1
bb1:
%0 = mul i32 1, 2
br bb2
bb2:
/// IR after splitEdge(bb0, bb1) using splitBasicBlock
bb0:
br bb1
bb1:
br bb1.split
bb1.split:
%0 = mul i32 1, 2
br bb2
bb2:
/// IR after splitEdge(bb0, bb1) using splitBasicBlockBefore
bb0:
br bb1.split
bb1.split
br bb1
bb1:
%0 = mul i32 1, 2
br bb2
bb2:
Differential Revision: https://reviews.llvm.org/D92200
507 lines
15 KiB
C++
507 lines
15 KiB
C++
//===- BasicBlockUtils.cpp - Unit tests for BasicBlockUtils ---------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/BasicAliasAnalysis.h"
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#include "llvm/Analysis/BlockFrequencyInfo.h"
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#include "llvm/Analysis/BranchProbabilityInfo.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/MemorySSA.h"
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#include "llvm/Analysis/MemorySSAUpdater.h"
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#include "llvm/Analysis/PostDominators.h"
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#include "llvm/Analysis/TargetLibraryInfo.h"
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#include "llvm/AsmParser/Parser.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/Support/SourceMgr.h"
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#include "gtest/gtest.h"
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using namespace llvm;
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static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
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SMDiagnostic Err;
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std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
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if (!Mod)
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Err.print("BasicBlockUtilsTests", errs());
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return Mod;
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}
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static BasicBlock *getBasicBlockByName(Function &F, StringRef Name) {
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for (BasicBlock &BB : F)
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if (BB.getName() == Name)
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return &BB;
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llvm_unreachable("Expected to find basic block!");
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}
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TEST(BasicBlockUtils, EliminateUnreachableBlocks) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(
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C,
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"define i32 @has_unreachable(i1 %cond) {\n"
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"entry:\n"
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" br i1 %cond, label %bb0, label %bb1\n"
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"bb0:\n"
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" br label %bb1\n"
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"bb1:\n"
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" %phi = phi i32 [ 0, %entry ], [ 1, %bb0 ]"
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" ret i32 %phi\n"
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"bb2:\n"
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" ret i32 42\n"
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"}\n"
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"\n"
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);
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auto *F = M->getFunction("has_unreachable");
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DominatorTree DT(*F);
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DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
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EXPECT_EQ(F->size(), (size_t)4);
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bool Result = EliminateUnreachableBlocks(*F, &DTU);
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EXPECT_TRUE(Result);
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EXPECT_EQ(F->size(), (size_t)3);
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EXPECT_TRUE(DT.verify());
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}
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TEST(BasicBlockUtils, SplitEdge_ex1) {
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LLVMContext C;
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std::unique_ptr<Module> M =
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parseIR(C, "define void @foo(i1 %cond0) {\n"
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"entry:\n"
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" br i1 %cond0, label %bb0, label %bb1\n"
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"bb0:\n"
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" %0 = mul i32 1, 2\n"
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" br label %bb1\n"
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"bb1:\n"
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" br label %bb2\n"
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"bb2:\n"
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" ret void\n"
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"}\n"
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"\n");
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Function *F = M->getFunction("foo");
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DominatorTree DT(*F);
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BasicBlock *SrcBlock;
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BasicBlock *DestBlock;
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BasicBlock *NewBB;
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SrcBlock = getBasicBlockByName(*F, "entry");
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DestBlock = getBasicBlockByName(*F, "bb0");
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NewBB = SplitEdge(SrcBlock, DestBlock, &DT, nullptr, nullptr);
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EXPECT_TRUE(DT.verify());
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EXPECT_EQ(NewBB->getSinglePredecessor(), SrcBlock);
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EXPECT_EQ(NewBB->getSingleSuccessor(), DestBlock);
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EXPECT_EQ(NewBB->getParent(), F);
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bool BBFlag = false;
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for (BasicBlock &BB : *F) {
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if (BB.getName() == NewBB->getName()) {
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BBFlag = true;
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}
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}
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EXPECT_TRUE(BBFlag);
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}
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TEST(BasicBlockUtils, SplitEdge_ex2) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(C, "define void @foo() {\n"
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"bb0:\n"
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" br label %bb2\n"
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"bb1:\n"
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" br label %bb2\n"
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"bb2:\n"
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" ret void\n"
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"}\n"
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"\n");
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Function *F = M->getFunction("foo");
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DominatorTree DT(*F);
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BasicBlock *SrcBlock;
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BasicBlock *DestBlock;
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BasicBlock *NewBB;
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SrcBlock = getBasicBlockByName(*F, "bb0");
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DestBlock = getBasicBlockByName(*F, "bb2");
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NewBB = SplitEdge(SrcBlock, DestBlock, &DT, nullptr, nullptr);
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EXPECT_TRUE(DT.verify());
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EXPECT_EQ(NewBB->getSinglePredecessor(), SrcBlock);
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EXPECT_EQ(NewBB->getSingleSuccessor(), DestBlock);
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EXPECT_EQ(NewBB->getParent(), F);
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bool BBFlag = false;
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for (BasicBlock &BB : *F) {
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if (BB.getName() == NewBB->getName()) {
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BBFlag = true;
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}
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}
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EXPECT_TRUE(BBFlag);
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}
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TEST(BasicBlockUtils, SplitEdge_ex3) {
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LLVMContext C;
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std::unique_ptr<Module> M =
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parseIR(C, "define i32 @foo(i32 %n) {\n"
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"entry:\n"
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" br label %header\n"
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"header:\n"
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" %sum.02 = phi i32 [ 0, %entry ], [ %sum.1, %bb3 ]\n"
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" %0 = phi i32 [ 0, %entry ], [ %4, %bb3 ] \n"
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" %1 = icmp slt i32 %0, %n \n"
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" br i1 %1, label %bb0, label %bb1\n"
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"bb0:\n"
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" %2 = add nsw i32 %sum.02, 2\n"
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" br label %bb2\n"
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"bb1:\n"
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" %3 = add nsw i32 %sum.02, 1\n"
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" br label %bb2\n"
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"bb2:\n"
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" %sum.1 = phi i32 [ %2, %bb0 ], [ %3, %bb1 ]\n"
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" br label %bb3\n"
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"bb3:\n"
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" %4 = add nsw i32 %0, 1 \n"
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" %5 = icmp slt i32 %4, 100\n"
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" br i1 %5, label %header, label %bb4\n"
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"bb4:\n"
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" %sum.0.lcssa = phi i32 [ %sum.1, %bb3 ]\n"
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" ret i32 %sum.0.lcssa\n"
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"}\n"
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"\n");
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Function *F = M->getFunction("foo");
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DominatorTree DT(*F);
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LoopInfo LI(DT);
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DataLayout DL("e-i64:64-f80:128-n8:16:32:64-S128");
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TargetLibraryInfoImpl TLII;
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TargetLibraryInfo TLI(TLII);
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AssumptionCache AC(*F);
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AAResults AA(TLI);
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BasicAAResult BAA(DL, *F, TLI, AC, &DT);
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AA.addAAResult(BAA);
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MemorySSA MSSA(*F, &AA, &DT);
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MemorySSAUpdater Updater(&MSSA);
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BasicBlock *SrcBlock;
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BasicBlock *DestBlock;
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BasicBlock *NewBB;
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SrcBlock = getBasicBlockByName(*F, "header");
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DestBlock = getBasicBlockByName(*F, "bb0");
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NewBB = SplitEdge(SrcBlock, DestBlock, &DT, &LI, &Updater);
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Updater.getMemorySSA()->verifyMemorySSA();
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EXPECT_TRUE(DT.verify());
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EXPECT_NE(LI.getLoopFor(SrcBlock), nullptr);
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EXPECT_NE(LI.getLoopFor(DestBlock), nullptr);
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EXPECT_NE(LI.getLoopFor(NewBB), nullptr);
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EXPECT_EQ(NewBB->getSinglePredecessor(), SrcBlock);
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EXPECT_EQ(NewBB->getSingleSuccessor(), DestBlock);
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EXPECT_EQ(NewBB->getParent(), F);
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bool BBFlag = false;
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for (BasicBlock &BB : *F) {
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if (BB.getName() == NewBB->getName()) {
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BBFlag = true;
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}
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}
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EXPECT_TRUE(BBFlag);
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}
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TEST(BasicBlockUtils, splitBasicBlockBefore_ex1) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(C, "define void @foo() {\n"
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"bb0:\n"
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" %0 = mul i32 1, 2\n"
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" br label %bb2\n"
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"bb1:\n"
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" br label %bb3\n"
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"bb2:\n"
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" %1 = phi i32 [ %0, %bb0 ]\n"
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" br label %bb3\n"
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"bb3:\n"
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" ret void\n"
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"}\n"
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"\n");
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Function *F = M->getFunction("foo");
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DominatorTree DT(*F);
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BasicBlock *DestBlock;
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BasicBlock *NewBB;
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DestBlock = getBasicBlockByName(*F, "bb2");
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NewBB = DestBlock->splitBasicBlockBefore(DestBlock->front().getIterator(),
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"test");
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PHINode *PN = dyn_cast<PHINode>(&(DestBlock->front()));
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EXPECT_EQ(PN->getIncomingBlock(0), NewBB);
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EXPECT_EQ(NewBB->getName(), "test");
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EXPECT_EQ(NewBB->getSingleSuccessor(), DestBlock);
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EXPECT_EQ(DestBlock->getSinglePredecessor(), NewBB);
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}
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#ifndef NDEBUG
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TEST(BasicBlockUtils, splitBasicBlockBefore_ex2) {
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LLVMContext C;
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std::unique_ptr<Module> M =
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parseIR(C, "define void @foo() {\n"
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"bb0:\n"
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" %0 = mul i32 1, 2\n"
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" br label %bb2\n"
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"bb1:\n"
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" br label %bb2\n"
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"bb2:\n"
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" %1 = phi i32 [ %0, %bb0 ], [ 1, %bb1 ]\n"
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" br label %bb3\n"
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"bb3:\n"
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" ret void\n"
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"}\n"
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"\n");
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Function *F = M->getFunction("foo");
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DominatorTree DT(*F);
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BasicBlock *DestBlock;
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DestBlock = getBasicBlockByName(*F, "bb2");
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ASSERT_DEATH(
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{
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DestBlock->splitBasicBlockBefore(DestBlock->front().getIterator(),
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"test");
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},
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"cannot split on multi incoming phis");
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}
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#endif
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TEST(BasicBlockUtils, NoUnreachableBlocksToEliminate) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(
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C,
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"define i32 @no_unreachable(i1 %cond) {\n"
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"entry:\n"
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" br i1 %cond, label %bb0, label %bb1\n"
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"bb0:\n"
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" br label %bb1\n"
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"bb1:\n"
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" %phi = phi i32 [ 0, %entry ], [ 1, %bb0 ]"
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" ret i32 %phi\n"
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"}\n"
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"\n"
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);
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auto *F = M->getFunction("no_unreachable");
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DominatorTree DT(*F);
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DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
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EXPECT_EQ(F->size(), (size_t)3);
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bool Result = EliminateUnreachableBlocks(*F, &DTU);
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EXPECT_FALSE(Result);
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EXPECT_EQ(F->size(), (size_t)3);
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EXPECT_TRUE(DT.verify());
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}
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TEST(BasicBlockUtils, SplitBlockPredecessors) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(
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C,
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"define i32 @basic_func(i1 %cond) {\n"
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"entry:\n"
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" br i1 %cond, label %bb0, label %bb1\n"
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"bb0:\n"
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" br label %bb1\n"
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"bb1:\n"
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" %phi = phi i32 [ 0, %entry ], [ 1, %bb0 ]"
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" ret i32 %phi\n"
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"}\n"
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"\n"
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);
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auto *F = M->getFunction("basic_func");
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DominatorTree DT(*F);
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// Make sure the dominator tree is properly updated if calling this on the
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// entry block.
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SplitBlockPredecessors(&F->getEntryBlock(), {}, "split.entry", &DT);
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EXPECT_TRUE(DT.verify());
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}
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TEST(BasicBlockUtils, SplitCriticalEdge) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(
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C,
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"define void @crit_edge(i1 %cond0, i1 %cond1) {\n"
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"entry:\n"
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" br i1 %cond0, label %bb0, label %bb1\n"
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"bb0:\n"
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" br label %bb1\n"
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"bb1:\n"
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" br label %bb2\n"
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"bb2:\n"
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" ret void\n"
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"}\n"
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"\n"
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);
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auto *F = M->getFunction("crit_edge");
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DominatorTree DT(*F);
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PostDominatorTree PDT(*F);
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CriticalEdgeSplittingOptions CESO(&DT, nullptr, nullptr, &PDT);
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EXPECT_EQ(1u, SplitAllCriticalEdges(*F, CESO));
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EXPECT_TRUE(DT.verify());
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EXPECT_TRUE(PDT.verify());
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}
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TEST(BasicBlockUtils, SplitIndirectBrCriticalEdge) {
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LLVMContext C;
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std::unique_ptr<Module> M =
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parseIR(C, "define void @crit_edge(i8* %cond0, i1 %cond1) {\n"
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"entry:\n"
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" indirectbr i8* %cond0, [label %bb0, label %bb1]\n"
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"bb0:\n"
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" br label %bb1\n"
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"bb1:\n"
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" %p = phi i32 [0, %bb0], [0, %entry]\n"
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" br i1 %cond1, label %bb2, label %bb3\n"
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"bb2:\n"
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" ret void\n"
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"bb3:\n"
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" ret void\n"
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"}\n");
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auto *F = M->getFunction("crit_edge");
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DominatorTree DT(*F);
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LoopInfo LI(DT);
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BranchProbabilityInfo BPI(*F, LI);
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BlockFrequencyInfo BFI(*F, BPI, LI);
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auto Block = [&F](StringRef BBName) -> const BasicBlock & {
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for (auto &BB : *F)
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if (BB.getName() == BBName)
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return BB;
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llvm_unreachable("Block not found");
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};
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bool Split = SplitIndirectBrCriticalEdges(*F, &BPI, &BFI);
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EXPECT_TRUE(Split);
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// Check that successors of the split block get their probability correct.
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BasicBlock *SplitBB = Block("bb1").getTerminator()->getSuccessor(0);
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EXPECT_EQ(2u, SplitBB->getTerminator()->getNumSuccessors());
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EXPECT_EQ(BranchProbability(1, 2), BPI.getEdgeProbability(SplitBB, 0u));
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EXPECT_EQ(BranchProbability(1, 2), BPI.getEdgeProbability(SplitBB, 1u));
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}
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TEST(BasicBlockUtils, SetEdgeProbability) {
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LLVMContext C;
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std::unique_ptr<Module> M = parseIR(
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C, "define void @edge_probability(i32 %0) {\n"
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"entry:\n"
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"switch i32 %0, label %LD [\n"
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" i32 700, label %L0\n"
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" i32 701, label %L1\n"
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" i32 702, label %L2\n"
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" i32 703, label %L3\n"
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" i32 704, label %L4\n"
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" i32 705, label %L5\n"
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" i32 706, label %L6\n"
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" i32 707, label %L7\n"
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" i32 708, label %L8\n"
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" i32 709, label %L9\n"
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" i32 710, label %L10\n"
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" i32 711, label %L11\n"
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" i32 712, label %L12\n"
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" i32 713, label %L13\n"
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" i32 714, label %L14\n"
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" i32 715, label %L15\n"
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" i32 716, label %L16\n"
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" i32 717, label %L17\n"
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" i32 718, label %L18\n"
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" i32 719, label %L19\n"
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"], !prof !{!\"branch_weights\", i32 1, i32 1, i32 1, i32 1, i32 1, "
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"i32 451, i32 1, i32 12, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, "
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"i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1}\n"
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"LD:\n"
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" unreachable\n"
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"L0:\n"
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" ret void\n"
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"L1:\n"
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" ret void\n"
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"L2:\n"
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" ret void\n"
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"L3:\n"
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" ret void\n"
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"L4:\n"
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" ret void\n"
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"L5:\n"
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" ret void\n"
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"L6:\n"
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" ret void\n"
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"L7:\n"
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" ret void\n"
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"L8:\n"
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" ret void\n"
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|
"L9:\n"
|
|
" ret void\n"
|
|
"L10:\n"
|
|
" ret void\n"
|
|
"L11:\n"
|
|
" ret void\n"
|
|
"L12:\n"
|
|
" ret void\n"
|
|
"L13:\n"
|
|
" ret void\n"
|
|
"L14:\n"
|
|
" ret void\n"
|
|
"L15:\n"
|
|
" ret void\n"
|
|
"L16:\n"
|
|
" ret void\n"
|
|
"L17:\n"
|
|
" ret void\n"
|
|
"L18:\n"
|
|
" ret void\n"
|
|
"L19:\n"
|
|
" ret void\n"
|
|
"}\n");
|
|
|
|
auto *F = M->getFunction("edge_probability");
|
|
DominatorTree DT(*F);
|
|
LoopInfo LI(DT);
|
|
BranchProbabilityInfo BPI(*F, LI);
|
|
|
|
auto Block = [&F](StringRef BBName) -> const BasicBlock & {
|
|
for (auto &BB : *F)
|
|
if (BB.getName() == BBName)
|
|
return BB;
|
|
llvm_unreachable("Block not found");
|
|
};
|
|
|
|
// Check that the unreachable block has the minimal probability.
|
|
const BasicBlock &EntryBB = Block("entry");
|
|
const BasicBlock &UnreachableBB = Block("LD");
|
|
EXPECT_EQ(BranchProbability::getRaw(1),
|
|
BPI.getEdgeProbability(&EntryBB, &UnreachableBB));
|
|
}
|