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//===- DAGISelEmitter.cpp - Generate an instruction selector --------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This tablegen backend emits a DAG instruction selector.
//
//===----------------------------------------------------------------------===//
#include "CodeGenDAGPatterns.h"
#include "DAGISelMatcher.h"
#include "llvm/Support/Debug.h"
#include "llvm/TableGen/Record.h"
#include "llvm/TableGen/TableGenBackend.h"
using namespace llvm;
#define DEBUG_TYPE "dag-isel-emitter"
namespace {
/// DAGISelEmitter - The top-level class which coordinates construction
/// and emission of the instruction selector.
class DAGISelEmitter {
RecordKeeper &Records; // Just so we can get at the timing functions.
CodeGenDAGPatterns CGP;
public:
explicit DAGISelEmitter(RecordKeeper &R) : Records(R), CGP(R) {}
void run(raw_ostream &OS);
};
} // End anonymous namespace
//===----------------------------------------------------------------------===//
// DAGISelEmitter Helper methods
//
/// getResultPatternCost - Compute the number of instructions for this pattern.
/// This is a temporary hack. We should really include the instruction
/// latencies in this calculation.
static unsigned getResultPatternCost(TreePatternNode *P,
CodeGenDAGPatterns &CGP) {
if (P->isLeaf()) return 0;
unsigned Cost = 0;
Record *Op = P->getOperator();
if (Op->isSubClassOf("Instruction")) {
Cost++;
CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
if (II.usesCustomInserter)
Cost += 10;
}
for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
Cost += getResultPatternCost(P->getChild(i), CGP);
return Cost;
}
/// getResultPatternCodeSize - Compute the code size of instructions for this
/// pattern.
static unsigned getResultPatternSize(TreePatternNode *P,
CodeGenDAGPatterns &CGP) {
if (P->isLeaf()) return 0;
unsigned Cost = 0;
Record *Op = P->getOperator();
if (Op->isSubClassOf("Instruction")) {
Cost += Op->getValueAsInt("CodeSize");
}
for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
Cost += getResultPatternSize(P->getChild(i), CGP);
return Cost;
}
namespace {
// PatternSortingPredicate - return true if we prefer to match LHS before RHS.
// In particular, we want to match maximal patterns first and lowest cost within
// a particular complexity first.
struct PatternSortingPredicate {
PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
CodeGenDAGPatterns &CGP;
bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
const TreePatternNode *LT = LHS->getSrcPattern();
const TreePatternNode *RT = RHS->getSrcPattern();
MVT LHSVT = LT->getNumTypes() != 0 ? LT->getSimpleType(0) : MVT::Other;
MVT RHSVT = RT->getNumTypes() != 0 ? RT->getSimpleType(0) : MVT::Other;
if (LHSVT.isVector() != RHSVT.isVector())
return RHSVT.isVector();
if (LHSVT.isFloatingPoint() != RHSVT.isFloatingPoint())
return RHSVT.isFloatingPoint();
// Otherwise, if the patterns might both match, sort based on complexity,
// which means that we prefer to match patterns that cover more nodes in the
// input over nodes that cover fewer.
int LHSSize = LHS->getPatternComplexity(CGP);
int RHSSize = RHS->getPatternComplexity(CGP);
if (LHSSize > RHSSize) return true; // LHS -> bigger -> less cost
if (LHSSize < RHSSize) return false;
// If the patterns have equal complexity, compare generated instruction cost
unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
if (LHSCost < RHSCost) return true;
if (LHSCost > RHSCost) return false;
unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
if (LHSPatSize < RHSPatSize) return true;
if (LHSPatSize > RHSPatSize) return false;
// Sort based on the UID of the pattern, to reflect source order.
// Note that this is not guaranteed to be unique, since a single source
// pattern may have been resolved into multiple match patterns due to
// alternative fragments. To ensure deterministic output, always use
// std::stable_sort with this predicate.
return LHS->ID < RHS->ID;
}
};
} // End anonymous namespace
void DAGISelEmitter::run(raw_ostream &OS) {
emitSourceFileHeader("DAG Instruction Selector for the " +
CGP.getTargetInfo().getName().str() + " target", OS);
OS << "// *** NOTE: This file is #included into the middle of the target\n"
<< "// *** instruction selector class. These functions are really "
<< "methods.\n\n";
OS << "// If GET_DAGISEL_DECL is #defined with any value, only function\n"
"// declarations will be included when this file is included.\n"
"// If GET_DAGISEL_BODY is #defined, its value should be the name of\n"
"// the instruction selector class. Function bodies will be emitted\n"
"// and each function's name will be qualified with the name of the\n"
"// class.\n"
"//\n"
"// When neither of the GET_DAGISEL* macros is defined, the functions\n"
"// are emitted inline.\n\n";
LLVM_DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
E = CGP.ptm_end();
I != E; ++I) {
errs() << "PATTERN: ";
I->getSrcPattern()->dump();
errs() << "\nRESULT: ";
I->getDstPattern()->dump();
errs() << "\n";
});
// Add all the patterns to a temporary list so we can sort them.
Records.startTimer("Sort patterns");
std::vector<const PatternToMatch*> Patterns;
for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
I != E; ++I)
Patterns.push_back(&*I);
// We want to process the matches in order of minimal cost. Sort the patterns
// so the least cost one is at the start.
llvm::stable_sort(Patterns, PatternSortingPredicate(CGP));
// Convert each variant of each pattern into a Matcher.
Records.startTimer("Convert to matchers");
std::vector<Matcher*> PatternMatchers;
for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
for (unsigned Variant = 0; ; ++Variant) {
if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
PatternMatchers.push_back(M);
else
break;
}
}
std::unique_ptr<Matcher> TheMatcher =
std::make_unique<ScopeMatcher>(PatternMatchers);
Records.startTimer("Optimize matchers");
OptimizeMatcher(TheMatcher, CGP);
//Matcher->dump();
Records.startTimer("Emit matcher table");
EmitMatcherTable(TheMatcher.get(), CGP, OS);
}
namespace llvm {
void EmitDAGISel(RecordKeeper &RK, raw_ostream &OS) {
RK.startTimer("Parse patterns");
DAGISelEmitter(RK).run(OS);
}
} // End llvm namespace
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