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Revert "[IRSim] Adding structural comparison to IRSimilarityCandidate."

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This reverts commit b27db2bb68163fa5bcb4a8f631a305eb5adb44e5.
This commit is contained in:
Andrew Litteken 2020-09-23 22:40:37 -05:00
parent 5b31a525de
commit d5678d1cef
3 changed files with 2 additions and 312 deletions
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54
include/llvm/Analysis/IRSimilarityIdentifier.h
View File

@ -410,28 +410,6 @@ struct IRInstructionMapper {
/// The \ref isSimilar function compares each IRInstructionData against one
/// another and if we have the same sequences of IRInstructionData that would
/// create the same hash, we have similar IRSimilarityCandidates.
///
/// We can also compare the structure of IRSimilarityCandidates. If we can
/// create a mapping of registers in the region contained by one
/// IRSimilarityCandidate to the region contained by different
/// IRSimilarityCandidate, they can be considered structurally similar.
///
/// IRSimilarityCandidate1: IRSimilarityCandidate2:
/// %add1 = add i32 %a, %b %add1 = add i32 %d, %e
/// %add2 = add i32 %a, %c %add2 = add i32 %d, %f
/// %add3 = add i32 c1, c2 %add3 = add i32 c3, c4
///
/// Can have the following mapping from candidate to candidate of:
/// %a -> %d, %b -> %e, %c -> %f, c1 -> c3, c2 -> c4
/// and can be considered similar.
///
/// IRSimilarityCandidate1: IRSimilarityCandidate2:
/// %add1 = add i32 %a, %b %add1 = add i32 %d, c4
/// %add2 = add i32 %a, %c %add2 = add i32 %d, %f
/// %add3 = add i32 c1, c2 %add3 = add i32 c3, c4
///
/// We cannot create the same mapping since the use of c4 is not used in the
/// same way as %b or c2.
class IRSimilarityCandidate {
private:
/// The start index of this IRSimilarityCandidate in the instruction list.
@ -470,37 +448,6 @@ public:
/// IRInstructionData in \p B.
static bool isSimilar(const IRSimilarityCandidate &A,
const IRSimilarityCandidate &B);
/// \param A - The first IRInstructionCandidate to compare.
/// \param B - The second IRInstructionCandidate to compare.
/// \returns True when every IRInstructionData in \p A is structurally similar
/// to \p B.
static bool compareStructure(const IRSimilarityCandidate &A,
const IRSimilarityCandidate &B);
struct OperandMapping {
/// The IRSimilarityCandidate that holds the instruction the OperVals were
/// pulled from.
const IRSimilarityCandidate &IRSC;
/// The operand values to be analyzed.
ArrayRef<Value *> &OperVals;
/// The current mapping of global value numbers from one IRSimilarityCandidate
/// to another IRSimilarityCandidate.
DenseMap<unsigned, DenseSet<unsigned>> &ValueNumberMapping;
};
/// Compare the operands in \p A and \p B and check that the current mapping
/// of global value numbers from \p A to \p B and \p B to \A is consistent.
///
/// \param A - The first IRInstructionCandidate, operand values, and current
/// operand mappings to compare.
/// \param B - The second IRInstructionCandidate, operand values, and current
/// operand mappings to compare.
/// \returns true if the IRSimilarityCandidates operands are compatible.
static bool compareOperandMapping(OperandMapping A, OperandMapping B);
/// Compare the start and end indices of the two IRSimilarityCandidates for
/// whether they overlap. If the start instruction of one
/// IRSimilarityCandidate is less than the end instruction of the other, and
@ -574,7 +521,6 @@ public:
iterator begin() const { return iterator(front()); }
iterator end() const { return std::next(iterator(back())); }
};
} // end namespace IRSimilarity
} // end namespace llvm

154
lib/Analysis/IRSimilarityIdentifier.cpp
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@ -239,160 +239,6 @@ bool IRSimilarityCandidate::isSimilar(const IRSimilarityCandidate &A,
});
}
/// Determine if operand number \p TargetArgVal is in the current mapping set
/// for operand number \p SourceArgVal.
///
/// \param [in, out] CurrentSrcTgtNumberMapping current mapping of global
/// value numbers from source IRSimilarityCandidate to target
/// IRSimilarityCandidate.
/// \param [in] SourceArgVal The global value number for an operand in the
/// in the original candidate.
/// \param [in] TargetArgVal The global value number for the corresponding
/// operand in the other candidate.
/// \returns True if there exists a mapping and false if not.
bool checkNumberingAndReplace(
DenseMap<unsigned, DenseSet<unsigned>> &CurrentSrcTgtNumberMapping,
unsigned SourceArgVal, unsigned TargetArgVal) {
// We are given two unsigned integers representing the global values of
// the operands in different IRSimilarityCandidates and a current mapping
// between the two.
//
// Source Operand GVN: 1
// Target Operand GVN: 2
// CurrentMapping: {1: {1, 2}}
//
// Since we have mapping, and the target operand is contained in the set, we
// update it to:
// CurrentMapping: {1: {2}}
// and can return true. But, if the mapping was
// CurrentMapping: {1: {3}}
// we would return false.
bool WasInserted;
DenseMap<unsigned, DenseSet<unsigned>>::iterator Val;
std::tie(Val, WasInserted) = CurrentSrcTgtNumberMapping.insert(
std::make_pair(SourceArgVal, DenseSet<unsigned>({TargetArgVal})));
// If we created a new mapping, then we are done.
if (WasInserted)
return true;
// If there is more than one option in the mapping set, and the target value
// is included in the mapping set replace that set with one that only includes
// the target value, as it is the only valid mapping via the non commutative
// instruction.
DenseSet<unsigned> &TargetSet = Val->second;
if (TargetSet.size() > 1 && TargetSet.find(TargetArgVal) != TargetSet.end()) {
TargetSet.clear();
TargetSet.insert(TargetArgVal);
return true;
}
// Return true if we can find the value in the set.
return TargetSet.find(TargetArgVal) != TargetSet.end();
}
bool IRSimilarityCandidate::compareOperandMapping(OperandMapping A,
OperandMapping B) {
// Iterators to keep track of where we are in the operands for each
// Instruction.
ArrayRef<Value *>::iterator VItA = A.OperVals.begin();
ArrayRef<Value *>::iterator VItB = B.OperVals.begin();
unsigned OperandLength = A.OperVals.size();
// For each operand, get the value numbering and ensure it is consistent.
for (unsigned Idx = 0; Idx < OperandLength; Idx++, VItA++, VItB++) {
unsigned OperValA = A.IRSC.ValueToNumber.find(*VItA)->second;
unsigned OperValB = B.IRSC.ValueToNumber.find(*VItB)->second;
// Attempt to add a set with only the target value. If there is no mapping
// we can create it here.
//
// For an instruction like a subtraction:
// IRSimilarityCandidateA: IRSimilarityCandidateB:
// %resultA = sub %a, %b %resultB = sub %d, %e
//
// We map %a -> %d and %b -> %e.
//
// And check to see whether their mapping is consistent in
// checkNumberingAndReplace.
if (!checkNumberingAndReplace(A.ValueNumberMapping, OperValA, OperValB))
return false;
if (!checkNumberingAndReplace(B.ValueNumberMapping, OperValB, OperValA))
return false;
}
return true;
}
bool IRSimilarityCandidate::compareStructure(const IRSimilarityCandidate &A,
const IRSimilarityCandidate &B) {
if (A.getLength() != B.getLength())
return false;
if (A.ValueToNumber.size() != B.ValueToNumber.size())
return false;
iterator ItA = A.begin();
iterator ItB = B.begin();
// These sets create a create a mapping between the values in one candidate
// to values in the other candidate. If we create a set with one element,
// and that same element maps to the original element in the candidate
// we have a good mapping.
DenseMap<unsigned, DenseSet<unsigned>> ValueNumberMappingA;
DenseMap<unsigned, DenseSet<unsigned>> ValueNumberMappingB;
DenseMap<unsigned, DenseSet<unsigned>>::iterator ValueMappingIt;
bool WasInserted;
// Iterate over the instructions contained in each candidate
unsigned SectionLength = A.getStartIdx() + A.getLength();
for (unsigned Loc = A.getStartIdx(); Loc < SectionLength;
ItA++, ItB++, Loc++) {
// Make sure the instructions are similar to one another.
if (!isClose(*ItA, *ItB))
return false;
Instruction *IA = ItA->Inst;
Instruction *IB = ItB->Inst;
if (!ItA->Legal || !ItB->Legal)
return false;
// Get the operand sets for the instructions.
ArrayRef<Value *> OperValsA = ItA->OperVals;
ArrayRef<Value *> OperValsB = ItB->OperVals;
unsigned InstValA = A.ValueToNumber.find(IA)->second;
unsigned InstValB = B.ValueToNumber.find(IB)->second;
// Ensure that the mappings for the instructions exists.
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingA.insert(
std::make_pair(InstValA, DenseSet<unsigned>({InstValB})));
if (!WasInserted && ValueMappingIt->second.find(InstValB) ==
ValueMappingIt->second.end())
return false;
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingB.insert(
std::make_pair(InstValB, DenseSet<unsigned>({InstValA})));
if (!WasInserted && ValueMappingIt->second.find(InstValA) ==
ValueMappingIt->second.end())
return false;
// TODO: Handle commutative instructions by mapping one operand to many
// operands instead only mapping a single operand to a single operand.
if (!compareOperandMapping({A, OperValsA, ValueNumberMappingA},
{B, OperValsB, ValueNumberMappingB}))
return false;
}
return true;
}
bool IRSimilarityCandidate::overlap(const IRSimilarityCandidate &A,
const IRSimilarityCandidate &B) {
auto DoesOverlap = [](const IRSimilarityCandidate &X,

106
unittests/Analysis/IRSimilarityIdentifierTest.cpp
View File

@ -11,13 +11,13 @@
//
//===----------------------------------------------------------------------===//
#include "gtest/gtest.h"
#include "llvm/Analysis/IRSimilarityIdentifier.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
using namespace llvm;
using namespace IRSimilarity;
@ -1311,8 +1311,7 @@ TEST(IRInstructionMapper, RepeatedIllegalLength) {
// A helper function that accepts an instruction list from a module made up of
// two blocks of two legal instructions and terminator, and checks them for
// instruction similarity.
static bool longSimCandCompare(std::vector<IRInstructionData *> &InstrList,
bool Structure = false) {
static bool longSimCandCompare(std::vector<IRInstructionData *> &InstrList) {
std::vector<IRInstructionData *>::iterator Start, End;
Start = InstrList.begin();
@ -1327,8 +1326,6 @@ static bool longSimCandCompare(std::vector<IRInstructionData *> &InstrList,
std::advance(Start, 3);
std::advance(End, 4);
IRSimilarityCandidate Cand2(3, 2, *Start, *End);
if (Structure)
return IRSimilarityCandidate::compareStructure(Cand1, Cand2);
return IRSimilarityCandidate::isSimilar(Cand1, Cand2);
}
@ -1526,102 +1523,3 @@ TEST(IRSimilarityCandidate, IllegalInCandidate) {
IRSimilarityCandidate Cand2(3, 3, *Start, *End);
ASSERT_FALSE(IRSimilarityCandidate::isSimilar(Cand1, Cand2));
}
// Checks that different structure, in this case, where we introduce a new
// needed input in one region, is recognized as different.
TEST(IRSimilarityCandidate, DifferentStructure) {
StringRef ModuleString = R"(
define i32 @f(i32 %a, i32 %b) {
bb0:
%0 = add i32 %a, %b
%1 = add i32 %b, %a
ret i32 0
bb1:
%2 = add i32 %a, %b
%3 = add i32 %b, %0
ret i32 0
})";
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
std::vector<IRInstructionData *> InstrList;
std::vector<unsigned> UnsignedVec;
SpecificBumpPtrAllocator<IRInstructionData> InstDataAllocator;
SpecificBumpPtrAllocator<IRInstructionDataList> IDLAllocator;
IRInstructionMapper Mapper(&InstDataAllocator, &IDLAllocator);
getVectors(*M, Mapper, InstrList, UnsignedVec);
// Check to make sure that we have a long enough region.
ASSERT_EQ(InstrList.size(), static_cast<unsigned>(6));
// Check that the instructions were added correctly to both vectors.
ASSERT_TRUE(InstrList.size() == UnsignedVec.size());
ASSERT_FALSE(longSimCandCompare(InstrList, true));
}
// Checks that the same structure is recognized between two candidates. The
// items %a and %b are used in the same way in both sets of instructions.
TEST(IRSimilarityCandidate, SameStructure) {
StringRef ModuleString = R"(
define i32 @f(i32 %a, i32 %b) {
bb0:
%0 = add i32 %a, %b
%1 = sub i32 %b, %a
ret i32 0
bb1:
%2 = add i32 %a, %b
%3 = sub i32 %b, %a
ret i32 0
})";
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
std::vector<IRInstructionData *> InstrList;
std::vector<unsigned> UnsignedVec;
SpecificBumpPtrAllocator<IRInstructionData> InstDataAllocator;
SpecificBumpPtrAllocator<IRInstructionDataList> IDLAllocator;
IRInstructionMapper Mapper(&InstDataAllocator, &IDLAllocator);
getVectors(*M, Mapper, InstrList, UnsignedVec);
// Check to make sure that we have a long enough region.
ASSERT_EQ(InstrList.size(), static_cast<unsigned>(6));
// Check that the instructions were added correctly to both vectors.
ASSERT_TRUE(InstrList.size() == UnsignedVec.size());
ASSERT_TRUE(longSimCandCompare(InstrList, true));
}
// Checks that the same structure is recognized between two candidates. While
// the input names are reversed, they still perform the same overall operation.
TEST(IRSimilarityCandidate, DifferentNameSameStructure) {
StringRef ModuleString = R"(
define i32 @f(i32 %a, i32 %b) {
bb0:
%0 = add i32 %a, %b
%1 = add i32 %b, %a
ret i32 0
bb1:
%2 = add i32 %b, %a
%3 = add i32 %a, %b
ret i32 0
})";
LLVMContext Context;
std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
std::vector<IRInstructionData *> InstrList;
std::vector<unsigned> UnsignedVec;
SpecificBumpPtrAllocator<IRInstructionData> InstDataAllocator;
SpecificBumpPtrAllocator<IRInstructionDataList> IDLAllocator;
IRInstructionMapper Mapper(&InstDataAllocator, &IDLAllocator);
getVectors(*M, Mapper, InstrList, UnsignedVec);
// Check to make sure that we have a long enough region.
ASSERT_EQ(InstrList.size(), static_cast<unsigned>(6));
// Check that the instructions were added correctly to both vectors.
ASSERT_TRUE(InstrList.size() == UnsignedVec.size());
ASSERT_TRUE(longSimCandCompare(InstrList, true));
}