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llvm-mirror/unittests/Analysis/DDGTest.cpp
Bardia Mahjour 5052dcf3b2 [DDG] Fix duplicate edge removal during pi-block formation
When creating pi-blocks we try to avoid creating duplicate edges
between outside nodes and the pi-block when an edge is of the
same kind and direction as another one that has already been
created. We do this by keeping track of the edges in an
enumerated array called EdgeAlreadyCreated. The problem is that
this array is declared local to the loop that iterates over the
nodes in the pi-block, so the information gets lost every time a
new inside-node is iterated over. The fix is to move the
declaration to the outer loop.

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D94094
2021-01-07 10:31:11 -05:00

285 lines
11 KiB
C++

//===- DDGTest.cpp - DDGAnalysis 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/Analysis/DDG.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Dominators.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
using namespace llvm;
/// Build the DDG analysis for a loop and run the given test \p Test.
static void runTest(Module &M, StringRef FuncName,
function_ref<void(Function &F, LoopInfo &LI,
DependenceInfo &DI, ScalarEvolution &SE)>
Test) {
auto *F = M.getFunction(FuncName);
ASSERT_NE(F, nullptr) << "Could not find " << FuncName;
TargetLibraryInfoImpl TLII;
TargetLibraryInfo TLI(TLII);
AssumptionCache AC(*F);
DominatorTree DT(*F);
LoopInfo LI(DT);
ScalarEvolution SE(*F, TLI, AC, DT, LI);
AAResults AA(TLI);
DependenceInfo DI(F, &AA, &SE, &LI);
Test(*F, LI, DI, SE);
}
static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
const char *ModuleStr) {
SMDiagnostic Err;
return parseAssemblyString(ModuleStr, Err, Context);
}
TEST(DDGTest, getDependencies) {
const char *ModuleStr =
"target datalayout = \"e-m:e-i64:64-n32:64\"\n"
"target triple = \"powerpc64le-unknown-linux-gnu\"\n"
"\n"
"define dso_local void @foo(i32 signext %n, i32* noalias %A, i32* "
"noalias %B) {\n"
"entry:\n"
" %cmp1 = icmp sgt i32 %n, 0\n"
" br i1 %cmp1, label %for.body.preheader, label %for.end\n"
"\n"
"for.body.preheader:\n"
" %wide.trip.count = zext i32 %n to i64\n"
" br label %for.body\n"
" \n"
" for.body:\n"
" %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ "
"%indvars.iv.next, %for.body ]\n"
" %arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv\n"
" %0 = trunc i64 %indvars.iv to i32\n"
" store i32 %0, i32* %arrayidx, align 4\n"
" %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
" %arrayidx2 = getelementptr inbounds i32, i32* %A, i64 "
"%indvars.iv.next\n"
" %1 = load i32, i32* %arrayidx2, align 4\n"
" %add3 = add nsw i32 %1, 1\n"
" %arrayidx5 = getelementptr inbounds i32, i32* %B, i64 %indvars.iv\n"
" store i32 %add3, i32* %arrayidx5, align 4\n"
" %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
" br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
"\n"
"for.end.loopexit:\n"
" br label %for.end\n"
"\n"
"for.end:\n"
" ret void\n"
"}\n";
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
runTest(
*M, "foo",
[&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
Loop *L = *LI.begin();
assert(L && "expected the loop to be identified.");
DataDependenceGraph DDG(*L, LI, DI);
// Collect all the nodes that have an outgoing memory edge
// while collecting all memory edges as well. There should
// only be one node with an outgoing memory edge and there
// should only be one memory edge in the entire graph.
std::vector<DDGNode *> DependenceSourceNodes;
std::vector<DDGEdge *> MemoryEdges;
for (DDGNode *N : DDG) {
for (DDGEdge *E : *N) {
bool SourceAdded = false;
if (E->isMemoryDependence()) {
MemoryEdges.push_back(E);
if (!SourceAdded) {
DependenceSourceNodes.push_back(N);
SourceAdded = true;
}
}
}
}
EXPECT_EQ(DependenceSourceNodes.size(), 1ull);
EXPECT_EQ(MemoryEdges.size(), 1ull);
DataDependenceGraph::DependenceList DL;
DDG.getDependencies(*DependenceSourceNodes.back(),
MemoryEdges.back()->getTargetNode(), DL);
EXPECT_EQ(DL.size(), 1ull);
EXPECT_TRUE(DL.back()->isAnti());
EXPECT_EQ(DL.back()->getLevels(), 1u);
EXPECT_NE(DL.back()->getDistance(1), nullptr);
EXPECT_EQ(DL.back()->getDistance(1),
SE.getOne(DL.back()->getDistance(1)->getType()));
});
}
/// Test to make sure that when pi-blocks are formed, multiple edges of the same
/// kind and direction are collapsed into a single edge.
/// In the test below, %loadASubI belongs to an outside node, which has input
/// dependency with multiple load instructions in the pi-block containing
/// %loadBSubI. We expect a single memory dependence edge from the outside node
/// to this pi-block. The pi-block also contains %add and %add7 both of which
/// feed a phi in an outside node. We expect a single def-use edge from the
/// pi-block to the node containing that phi.
TEST(DDGTest, avoidDuplicateEdgesToFromPiBlocks) {
const char *ModuleStr =
"target datalayout = \"e-m:e-i64:64-n32:64-v256:256:256-v512:512:512\"\n"
"\n"
"define void @foo(float* noalias %A, float* noalias %B, float* noalias "
"%C, float* noalias %D, i32 signext %n) {\n"
"entry:\n"
" %cmp1 = icmp sgt i32 %n, 0\n"
" br i1 %cmp1, label %for.body.preheader, label %for.end\n"
"\n"
"for.body.preheader: ; preds = %entry\n"
" %wide.trip.count = zext i32 %n to i64\n"
" br label %for.body\n"
"\n"
"for.body: ; preds = "
"%for.body.preheader, %if.end\n"
" %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, "
"%if.end ]\n"
" %arrayidx = getelementptr inbounds float, float* %A, i64 %indvars.iv\n"
" %loadASubI = load float, float* %arrayidx, align 4\n"
" %arrayidx2 = getelementptr inbounds float, float* %B, i64 "
"%indvars.iv\n"
" %loadBSubI = load float, float* %arrayidx2, align 4\n"
" %add = fadd fast float %loadASubI, %loadBSubI\n"
" %arrayidx4 = getelementptr inbounds float, float* %A, i64 "
"%indvars.iv\n"
" store float %add, float* %arrayidx4, align 4\n"
" %arrayidx6 = getelementptr inbounds float, float* %A, i64 "
"%indvars.iv\n"
" %0 = load float, float* %arrayidx6, align 4\n"
" %add7 = fadd fast float %0, 1.000000e+00\n"
" %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1\n"
" %arrayidx10 = getelementptr inbounds float, float* %B, i64 "
"%indvars.iv.next\n"
" store float %add7, float* %arrayidx10, align 4\n"
" %arrayidx12 = getelementptr inbounds float, float* %A, i64 "
"%indvars.iv\n"
" %1 = load float, float* %arrayidx12, align 4\n"
" %cmp13 = fcmp fast ogt float %1, 1.000000e+02\n"
" br i1 %cmp13, label %if.then, label %if.else\n"
"\n"
"if.then: ; preds = %for.body\n"
" br label %if.end\n"
"\n"
"if.else: ; preds = %for.body\n"
" br label %if.end\n"
"\n"
"if.end: ; preds = %if.else, "
"%if.then\n"
" %ff.0 = phi float [ %add, %if.then ], [ %add7, %if.else ]\n"
" store float %ff.0, float* %C, align 4\n"
" %exitcond = icmp ne i64 %indvars.iv.next, %wide.trip.count\n"
" br i1 %exitcond, label %for.body, label %for.end.loopexit\n"
"\n"
"for.end.loopexit: ; preds = %if.end\n"
" br label %for.end\n"
"\n"
"for.end: ; preds = "
"%for.end.loopexit, %entry\n"
" ret void\n"
"}\n";
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleStr);
runTest(
*M, "foo",
[&](Function &F, LoopInfo &LI, DependenceInfo &DI, ScalarEvolution &SE) {
Loop *L = *LI.begin();
assert(L && "expected the loop to be identified.");
DataDependenceGraph DDG(*L, LI, DI);
const DDGNode *LoadASubI = nullptr;
for (DDGNode *N : DDG) {
if (!isa<SimpleDDGNode>(N))
continue;
SmallVector<Instruction *, 8> IList;
N->collectInstructions([](const Instruction *I) { return true; },
IList);
if (llvm::any_of(IList, [](Instruction *I) {
return I->getName() == "loadASubI";
})) {
LoadASubI = N;
break;
}
}
assert(LoadASubI && "Did not find load of A[i]");
const PiBlockDDGNode *PiBlockWithBSubI = nullptr;
for (DDGNode *N : DDG) {
if (!isa<PiBlockDDGNode>(N))
continue;
for (DDGNode *M : cast<PiBlockDDGNode>(N)->getNodes()) {
SmallVector<Instruction *, 8> IList;
M->collectInstructions([](const Instruction *I) { return true; },
IList);
if (llvm::any_of(IList, [](Instruction *I) {
return I->getName() == "loadBSubI";
})) {
PiBlockWithBSubI = static_cast<PiBlockDDGNode *>(N);
break;
}
}
if (PiBlockWithBSubI)
break;
}
assert(PiBlockWithBSubI &&
"Did not find pi-block containing load of B[i]");
const DDGNode *FFPhi = nullptr;
for (DDGNode *N : DDG) {
if (!isa<SimpleDDGNode>(N))
continue;
SmallVector<Instruction *, 8> IList;
N->collectInstructions([](const Instruction *I) { return true; },
IList);
if (llvm::any_of(IList, [](Instruction *I) {
return I->getName() == "ff.0";
})) {
FFPhi = N;
break;
}
}
assert(FFPhi && "Did not find ff.0 phi instruction");
// Expect a single memory edge from '%0 = A[i]' to the pi-block. This
// means the duplicate incoming memory edges are removed during pi-block
// formation.
SmallVector<DDGEdge *, 4> EL;
LoadASubI->findEdgesTo(*PiBlockWithBSubI, EL);
unsigned NumMemoryEdges = llvm::count_if(
EL, [](DDGEdge *Edge) { return Edge->isMemoryDependence(); });
EXPECT_EQ(NumMemoryEdges, 1ull);
/// Expect a single def-use edge from the pi-block to '%ff.0 = phi...`.
/// This means the duplicate outgoing def-use edges are removed during
/// pi-block formation.
EL.clear();
PiBlockWithBSubI->findEdgesTo(*FFPhi, EL);
NumMemoryEdges =
llvm::count_if(EL, [](DDGEdge *Edge) { return Edge->isDefUse(); });
EXPECT_EQ(NumMemoryEdges, 1ull);
});
}