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llvm-project/llvm/unittests/Analysis/DivergenceAnalysisTest.cpp

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//===- DivergenceAnalysisTest.cpp - DivergenceAnalysis unit tests ---------===//
//
// 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/ADT/SmallVector.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/DivergenceAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/SyncDependenceAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
namespace llvm {
namespace {
BasicBlock *GetBlockByName(StringRef BlockName, Function &F) {
for (auto &BB : F) {
if (BB.getName() != BlockName)
continue;
return &BB;
}
return nullptr;
}
// We use this fixture to ensure that we clean up DivergenceAnalysisImpl before
// deleting the PassManager.
class DivergenceAnalysisTest : public testing::Test {
protected:
LLVMContext Context;
Module M;
TargetLibraryInfoImpl TLII;
TargetLibraryInfo TLI;
std::unique_ptr<DominatorTree> DT;
std::unique_ptr<PostDominatorTree> PDT;
std::unique_ptr<LoopInfo> LI;
std::unique_ptr<SyncDependenceAnalysis> SDA;
DivergenceAnalysisTest() : M("", Context), TLII(), TLI(TLII) {}
DivergenceAnalysisImpl buildDA(Function &F, bool IsLCSSA) {
DT.reset(new DominatorTree(F));
PDT.reset(new PostDominatorTree(F));
LI.reset(new LoopInfo(*DT));
SDA.reset(new SyncDependenceAnalysis(*DT, *PDT, *LI));
return DivergenceAnalysisImpl(F, nullptr, *DT, *LI, *SDA, IsLCSSA);
}
void runWithDA(
Module &M, StringRef FuncName, bool IsLCSSA,
function_ref<void(Function &F, LoopInfo &LI, DivergenceAnalysisImpl &DA)>
Test) {
auto *F = M.getFunction(FuncName);
ASSERT_NE(F, nullptr) << "Could not find " << FuncName;
DivergenceAnalysisImpl DA = buildDA(*F, IsLCSSA);
Test(*F, *LI, DA);
}
};
// Simple initial state test
TEST_F(DivergenceAnalysisTest, DAInitialState) {
IntegerType *IntTy = IntegerType::getInt32Ty(Context);
FunctionType *FTy =
FunctionType::get(Type::getVoidTy(Context), {IntTy}, false);
Function *F = Function::Create(FTy, Function::ExternalLinkage, "f", M);
BasicBlock *BB = BasicBlock::Create(Context, "entry", F);
ReturnInst::Create(Context, nullptr, BB);
DivergenceAnalysisImpl DA = buildDA(*F, false);
// Whole function region
EXPECT_EQ(DA.getRegionLoop(), nullptr);
// No divergence in initial state
EXPECT_FALSE(DA.hasDetectedDivergence());
// No spurious divergence
DA.compute();
EXPECT_FALSE(DA.hasDetectedDivergence());
// Detected divergence after marking
Argument &arg = *F->arg_begin();
DA.markDivergent(arg);
EXPECT_TRUE(DA.hasDetectedDivergence());
EXPECT_TRUE(DA.isDivergent(arg));
DA.compute();
EXPECT_TRUE(DA.hasDetectedDivergence());
EXPECT_TRUE(DA.isDivergent(arg));
}
TEST_F(DivergenceAnalysisTest, DANoLCSSA) {
LLVMContext C;
SMDiagnostic Err;
std::unique_ptr<Module> M = parseAssemblyString(
"target datalayout = \"e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128\" "
" "
"define i32 @f_1(i8* nocapture %arr, i32 %n, i32* %A, i32* %B) "
" local_unnamed_addr { "
"entry: "
" br label %loop.ph "
" "
"loop.ph: "
" br label %loop "
" "
"loop: "
" %iv0 = phi i32 [ %iv0.inc, %loop ], [ 0, %loop.ph ] "
" %iv1 = phi i32 [ %iv1.inc, %loop ], [ -2147483648, %loop.ph ] "
" %iv0.inc = add i32 %iv0, 1 "
" %iv1.inc = add i32 %iv1, 3 "
" %cond.cont = icmp slt i32 %iv0, %n "
" br i1 %cond.cont, label %loop, label %for.end.loopexit "
" "
"for.end.loopexit: "
" ret i32 %iv0 "
"} ",
Err, C);
Function *F = M->getFunction("f_1");
DivergenceAnalysisImpl DA = buildDA(*F, false);
EXPECT_FALSE(DA.hasDetectedDivergence());
auto ItArg = F->arg_begin();
ItArg++;
auto &NArg = *ItArg;
// Seed divergence in argument %n
DA.markDivergent(NArg);
DA.compute();
EXPECT_TRUE(DA.hasDetectedDivergence());
// Verify that "ret %iv.0" is divergent
auto ItBlock = F->begin();
std::advance(ItBlock, 3);
auto &ExitBlock = *GetBlockByName("for.end.loopexit", *F);
auto &RetInst = *cast<ReturnInst>(ExitBlock.begin());
EXPECT_TRUE(DA.isDivergent(RetInst));
}
TEST_F(DivergenceAnalysisTest, DALCSSA) {
LLVMContext C;
SMDiagnostic Err;
std::unique_ptr<Module> M = parseAssemblyString(
"target datalayout = \"e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128\" "
" "
"define i32 @f_lcssa(i8* nocapture %arr, i32 %n, i32* %A, i32* %B) "
" local_unnamed_addr { "
"entry: "
" br label %loop.ph "
" "
"loop.ph: "
" br label %loop "
" "
"loop: "
" %iv0 = phi i32 [ %iv0.inc, %loop ], [ 0, %loop.ph ] "
" %iv1 = phi i32 [ %iv1.inc, %loop ], [ -2147483648, %loop.ph ] "
" %iv0.inc = add i32 %iv0, 1 "
" %iv1.inc = add i32 %iv1, 3 "
" %cond.cont = icmp slt i32 %iv0, %n "
" br i1 %cond.cont, label %loop, label %for.end.loopexit "
" "
"for.end.loopexit: "
" %val.ret = phi i32 [ %iv0, %loop ] "
" br label %detached.return "
" "
"detached.return: "
" ret i32 %val.ret "
"} ",
Err, C);
Function *F = M->getFunction("f_lcssa");
DivergenceAnalysisImpl DA = buildDA(*F, true);
EXPECT_FALSE(DA.hasDetectedDivergence());
auto ItArg = F->arg_begin();
ItArg++;
auto &NArg = *ItArg;
// Seed divergence in argument %n
DA.markDivergent(NArg);
DA.compute();
EXPECT_TRUE(DA.hasDetectedDivergence());
// Verify that "ret %iv.0" is divergent
auto ItBlock = F->begin();
std::advance(ItBlock, 4);
auto &ExitBlock = *GetBlockByName("detached.return", *F);
auto &RetInst = *cast<ReturnInst>(ExitBlock.begin());
EXPECT_TRUE(DA.isDivergent(RetInst));
}
TEST_F(DivergenceAnalysisTest, DAJoinDivergence) {
LLVMContext C;
SMDiagnostic Err;
std::unique_ptr<Module> M = parseAssemblyString(
"target datalayout = \"e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128\" "
" "
"define void @f_1(i1 %a, i1 %b, i1 %c) "
" local_unnamed_addr { "
"A: "
" br i1 %a, label %B, label %C "
" "
"B: "
" br i1 %b, label %C, label %D "
" "
"C: "
" %c.join = phi i32 [ 0, %A ], [ 1, %B ] "
" br i1 %c, label %D, label %E "
" "
"D: "
" %d.join = phi i32 [ 0, %B ], [ 1, %C ] "
" br label %E "
" "
"E: "
" %e.join = phi i32 [ 0, %C ], [ 1, %D ] "
" ret void "
"} "
" "
"define void @f_2(i1 %a, i1 %b, i1 %c) "
" local_unnamed_addr { "
"A: "
" br i1 %a, label %B, label %E "
" "
"B: "
" br i1 %b, label %C, label %D "
" "
"C: "
" br label %D "
" "
"D: "
" %d.join = phi i32 [ 0, %B ], [ 1, %C ] "
" br label %E "
" "
"E: "
" %e.join = phi i32 [ 0, %A ], [ 1, %D ] "
" ret void "
"} "
" "
"define void @f_3(i1 %a, i1 %b, i1 %c)"
" local_unnamed_addr { "
"A: "
" br i1 %a, label %B, label %C "
" "
"B: "
" br label %C "
" "
"C: "
" %c.join = phi i32 [ 0, %A ], [ 1, %B ] "
" br i1 %c, label %D, label %E "
" "
"D: "
" br label %E "
" "
"E: "
" %e.join = phi i32 [ 0, %C ], [ 1, %D ] "
" ret void "
"} ",
Err, C);
// Maps divergent conditions to the basic blocks whose Phi nodes become
// divergent. Blocks need to be listed in IR order.
using SmallBlockVec = SmallVector<const BasicBlock *, 4>;
using InducedDivJoinMap = std::map<const Value *, SmallBlockVec>;
// Actual function performing the checks.
auto CheckDivergenceFunc = [this](Function &F,
InducedDivJoinMap &ExpectedDivJoins) {
for (auto &ItCase : ExpectedDivJoins) {
auto *DivVal = ItCase.first;
auto DA = buildDA(F, false);
DA.markDivergent(*DivVal);
DA.compute();
// List of basic blocks that shall host divergent Phi nodes.
auto ItDivJoins = ItCase.second.begin();
for (auto &BB : F) {
auto *Phi = dyn_cast<PHINode>(BB.begin());
if (!Phi)
continue;
if (ItDivJoins != ItCase.second.end() && &BB == *ItDivJoins) {
EXPECT_TRUE(DA.isDivergent(*Phi));
// Advance to next block with expected divergent PHI node.
++ItDivJoins;
} else {
EXPECT_FALSE(DA.isDivergent(*Phi));
}
}
}
};
{
auto *F = M->getFunction("f_1");
auto ItBlocks = F->begin();
ItBlocks++; // Skip A
ItBlocks++; // Skip B
auto *C = &*ItBlocks++;
auto *D = &*ItBlocks++;
auto *E = &*ItBlocks;
auto ItArg = F->arg_begin();
auto *AArg = &*ItArg++;
auto *BArg = &*ItArg++;
auto *CArg = &*ItArg;
InducedDivJoinMap DivJoins;
DivJoins.emplace(AArg, SmallBlockVec({C, D, E}));
DivJoins.emplace(BArg, SmallBlockVec({D, E}));
DivJoins.emplace(CArg, SmallBlockVec({E}));
CheckDivergenceFunc(*F, DivJoins);
}
{
auto *F = M->getFunction("f_2");
auto ItBlocks = F->begin();
ItBlocks++; // Skip A
ItBlocks++; // Skip B
ItBlocks++; // Skip C
auto *D = &*ItBlocks++;
auto *E = &*ItBlocks;
auto ItArg = F->arg_begin();
auto *AArg = &*ItArg++;
auto *BArg = &*ItArg++;
auto *CArg = &*ItArg;
InducedDivJoinMap DivJoins;
DivJoins.emplace(AArg, SmallBlockVec({E}));
DivJoins.emplace(BArg, SmallBlockVec({D}));
DivJoins.emplace(CArg, SmallBlockVec({}));
CheckDivergenceFunc(*F, DivJoins);
}
{
auto *F = M->getFunction("f_3");
auto ItBlocks = F->begin();
ItBlocks++; // Skip A
ItBlocks++; // Skip B
auto *C = &*ItBlocks++;
ItBlocks++; // Skip D
auto *E = &*ItBlocks;
auto ItArg = F->arg_begin();
auto *AArg = &*ItArg++;
auto *BArg = &*ItArg++;
auto *CArg = &*ItArg;
InducedDivJoinMap DivJoins;
DivJoins.emplace(AArg, SmallBlockVec({C}));
DivJoins.emplace(BArg, SmallBlockVec({}));
DivJoins.emplace(CArg, SmallBlockVec({E}));
CheckDivergenceFunc(*F, DivJoins);
}
}
TEST_F(DivergenceAnalysisTest, DASwitchUnreachableDefault) {
LLVMContext C;
SMDiagnostic Err;
std::unique_ptr<Module> M = parseAssemblyString(
"target datalayout = \"e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128\" "
" "
"define void @switch_unreachable_default(i32 %cond) local_unnamed_addr { "
"entry: "
" switch i32 %cond, label %sw.default [ "
" i32 0, label %sw.bb0 "
" i32 1, label %sw.bb1 "
" ] "
" "
"sw.bb0: "
" br label %sw.epilog "
" "
"sw.bb1: "
" br label %sw.epilog "
" "
"sw.default: "
" unreachable "
" "
"sw.epilog: "
" %div.dbl = phi double [ 0.0, %sw.bb0], [ -1.0, %sw.bb1 ] "
" ret void "
"}",
Err, C);
auto *F = M->getFunction("switch_unreachable_default");
auto &CondArg = *F->arg_begin();
auto DA = buildDA(*F, false);
EXPECT_FALSE(DA.hasDetectedDivergence());
DA.markDivergent(CondArg);
DA.compute();
// Still %CondArg is divergent.
EXPECT_TRUE(DA.hasDetectedDivergence());
// The join uni.dbl is not divergent (see D52221)
auto &ExitBlock = *GetBlockByName("sw.epilog", *F);
auto &DivDblPhi = *cast<PHINode>(ExitBlock.begin());
EXPECT_TRUE(DA.isDivergent(DivDblPhi));
}
} // end anonymous namespace
} // end namespace llvm
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