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270 lines
9.4 KiB
C++
270 lines
9.4 KiB
C++
//===--- ConstantPropagation.cpp - Promote alloc_box to alloc_stack ------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "constant-propagation"
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#include "swift/AST/Builtins.h"
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#include "swift/AST/DiagnosticEngine.h"
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#include "swift/AST/Diagnostics.h"
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#include "swift/AST/Type.h"
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#include "swift/Subsystems.h"
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#include "swift/SIL/SILBuilder.h"
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#include "swift/SILPasses/Utils/Local.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringSwitch.h"
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#include "llvm/Support/Debug.h"
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using namespace swift;
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STATISTIC(NumInstFolded, "Number of constant folded instructions");
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template<typename...T, typename...U>
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static void diagnose(ASTContext &Context, SourceLoc loc, Diag<T...> diag,
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U &&...args) {
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Context.Diags.diagnose(loc,
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diag, std::forward<U>(args)...);
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}
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static SILInstruction *constantFoldIntrinsic(ApplyInst *AI,
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llvm::Intrinsic::ID ID,
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SILModule &M) {
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OperandValueArrayRef Args = AI->getArguments();
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if (Args.size() == 2) {
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// Check if both arguments are literals.
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if (IntegerLiteralInst *Op1 = dyn_cast<IntegerLiteralInst>(Args[0])) {
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if (IntegerLiteralInst *Op2 = dyn_cast<IntegerLiteralInst>(Args[1])) {
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switch (ID) {
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default: break;
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case llvm::Intrinsic::sadd_with_overflow:
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case llvm::Intrinsic::uadd_with_overflow:
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case llvm::Intrinsic::ssub_with_overflow:
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case llvm::Intrinsic::usub_with_overflow:
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case llvm::Intrinsic::smul_with_overflow:
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case llvm::Intrinsic::umul_with_overflow: {
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// Handle arithmetic intrinsics with overflow.
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// First, Calculate the result.
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APInt Res;
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bool Overflow;
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switch (ID) {
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default: llvm_unreachable("Invalid case");
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case llvm::Intrinsic::sadd_with_overflow:
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Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow);
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break;
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case llvm::Intrinsic::uadd_with_overflow:
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Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow);
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break;
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case llvm::Intrinsic::ssub_with_overflow:
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Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow);
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break;
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case llvm::Intrinsic::usub_with_overflow:
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Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow);
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break;
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case llvm::Intrinsic::smul_with_overflow:
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Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow);
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break;
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case llvm::Intrinsic::umul_with_overflow:
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Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow);
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break;
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}
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// Diagnose the overflow.
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if (Overflow) {
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diagnose(M.getASTContext(),
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AI->getLoc().getSourceLoc(),
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diag::arithmetic_operation_overflow);
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return nullptr;
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}
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// Get the SIL subtypes of the returned tuple type.
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SILType FuncResType = AI->getFunctionTypeInfo(M)->getResultType();
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TupleType *T = FuncResType.castTo<TupleType>();
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assert(T->getNumElements() == 2);
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SILType ResTy1 =
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SILType::getPrimitiveType(CanType(T->getElementType(0)),
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SILValueCategory::Object);
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SILType ResTy2 =
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SILType::getPrimitiveType(CanType(T->getElementType(1)),
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SILValueCategory::Object);
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// Construct the folded instruction - a tuple of two literals, the
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// result and overflow.
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SILBuilder B(AI);
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SILValue Result[] = {
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B.createIntegerLiteral(AI->getLoc(), ResTy1, Res),
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B.createIntegerLiteral(AI->getLoc(), ResTy2, Overflow)
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};
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return B.createTuple(AI->getLoc(), FuncResType, Result);
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}
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} // end of switch(ID)
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}
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}
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}
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return nullptr;
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}
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static SILInstruction *constantFoldBuiltin(ApplyInst *AI,
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BuiltinFunctionRefInst *FR,
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SILModule &M) {
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const IntrinsicInfo &Intrinsic = FR->getIntrinsicInfo();
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// If it's an llvm intrinsic, fold the intrinsic.
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if (Intrinsic.ID != llvm::Intrinsic::not_intrinsic) {
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return constantFoldIntrinsic(AI, Intrinsic.ID, M);
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}
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// Otherwise, it should be one of the builin functions.
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OperandValueArrayRef Args = AI->getArguments();
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const BuiltinInfo &Builtin = M.getBuiltinInfo(FR->getFunction());
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switch (Builtin.ID) {
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default: break;
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case BuiltinValueKind::Trunc:
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case BuiltinValueKind::ZExt:
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case BuiltinValueKind::SExt: {
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// We can fold if the value being cast is a constant.
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IntegerLiteralInst *V = dyn_cast<IntegerLiteralInst>(Args[0]);
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if (!V)
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return nullptr;
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// Get the cast result.
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APInt CastResV;
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Type DestTy = Builtin.Types.size() == 2 ? Builtin.Types[1] : Type();
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uint32_t DestBitWidth =
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DestTy->castTo<BuiltinIntegerType>()->getBitWidth();
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switch (Builtin.ID) {
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default : llvm_unreachable("Invalid case.");
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case BuiltinValueKind::Trunc:
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CastResV = V->getValue().trunc(DestBitWidth);
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break;
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case BuiltinValueKind::ZExt:
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CastResV = V->getValue().zext(DestBitWidth);
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break;
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case BuiltinValueKind::SExt:
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CastResV = V->getValue().sext(DestBitWidth);
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break;
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}
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// Add the literal instruction to represnet the result of the cast.
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SILBuilder B(AI);
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return B.createIntegerLiteral(AI->getLoc(),
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SILType::getPrimitiveType(CanType(DestTy),
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SILValueCategory::Object),
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CastResV);
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}
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}
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return nullptr;
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}
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static SILInstruction *constantFoldInstruction(SILInstruction &I,
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SILModule &M) {
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// Constant fold function calls.
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if (ApplyInst *AI = dyn_cast<ApplyInst>(&I)) {
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// Constant fold calls to builtins.
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if (BuiltinFunctionRefInst *FR =
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dyn_cast<BuiltinFunctionRefInst>(AI->getCallee().getDef())) {
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return constantFoldBuiltin(AI, FR, M);
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}
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return nullptr;
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}
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// Constant fold extraction of a constant element.
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if (TupleExtractInst *TEI = dyn_cast<TupleExtractInst>(&I)) {
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if (TupleInst *TheTuple = dyn_cast<TupleInst>(TEI->getOperand().getDef())) {
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unsigned FieldNo = TEI->getFieldNo();
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ValueBase *Elem = TheTuple->getElements()[FieldNo].getDef();
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if (IntegerLiteralInst *ConstElem = dyn_cast<IntegerLiteralInst>(Elem)) {
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return ConstElem;
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}
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}
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}
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// Constant fold extraction of a constant element.
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if (StructExtractInst *SEI = dyn_cast<StructExtractInst>(&I)) {
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if (StructInst *Struct = dyn_cast<StructInst>(SEI->getOperand().getDef())) {
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// Find the Field number corresponding to the FieldDecl.
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unsigned FieldNo = 0;
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StructDecl *SD =
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cast<StructDecl>(Struct->getType().getSwiftType()->getAnyNominal());
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for (auto MD : SD->getPhysicalFields()) {
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if (MD == SEI->getField()) {
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ValueBase *E = Struct->getElements()[FieldNo].getDef();
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// If the element the struct_extract is extraciong is const, fold it.
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if (IntegerLiteralInst *ConstE = dyn_cast<IntegerLiteralInst>(E)) {
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return ConstE;
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}
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break;
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}
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++FieldNo;
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}
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}
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}
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return nullptr;
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}
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static bool CCPFunctionBody(SILFunction &F, SILModule &M) {
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// Initialize the worklist to all of the instructions ready to process...
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std::set<SILInstruction*> WorkList;
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for (auto &BB : F) {
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for(auto &I : BB) {
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WorkList.insert(&I);
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}
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}
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// Try to fold instructions in the list one by one.
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bool Folded = false;
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while (!WorkList.empty()) {
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SILInstruction *I = *WorkList.begin();
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WorkList.erase(WorkList.begin());
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if (!I->use_empty())
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// Try to fold the instruction.
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if (SILInstruction *C = constantFoldInstruction(*I, M)) {
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// We were able to fold, so all users should use the new folded value.
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assert(I->getTypes().size() == 1 &&
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"Currently, we only support single result instructions.");
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SILValue(I).replaceAllUsesWith(C);
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// The users could be constant propagatable now.
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for (auto UseI = I->use_begin(),
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UseE = I->use_end(); UseI != UseE; ++UseI) {
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WorkList.insert(cast<SILInstruction>(UseI.getUser()));
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}
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// Remove the unused instruction.
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WorkList.erase(I);
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// Eagerly DCE.
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recursivelyDeleteTriviallyDeadInstructions(I);
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Folded = true;
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++NumInstFolded;
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}
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}
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return false;
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}
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//===----------------------------------------------------------------------===//
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// Top Level Driver
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//===----------------------------------------------------------------------===//
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void swift::performSILConstantPropagation(SILModule *M) {
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for (auto &Fn : *M) {
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CCPFunctionBody(Fn, *M);
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}
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}
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