mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4300 91177308-0d34-0410-b5e6-96231b3b80d8
175 lines
5.7 KiB
C++
175 lines
5.7 KiB
C++
//===-- InstSelectSimple.cpp - A simple instruction selector for x86 ------===//
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//
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// This file defines a simple peephole instruction selector for the x86 platform
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//
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//===----------------------------------------------------------------------===//
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#include "X86.h"
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#include "X86InstructionInfo.h"
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#include "llvm/Function.h"
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#include "llvm/iTerminators.h"
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#include "llvm/Type.h"
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#include "llvm/Constants.h"
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#include "llvm/CodeGen/MFunction.h"
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#include "llvm/CodeGen/MInstBuilder.h"
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#include "llvm/Support/InstVisitor.h"
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#include <map>
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namespace {
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struct ISel : public InstVisitor<ISel> { // eventually will be a FunctionPass
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MFunction *F; // The function we are compiling into
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MBasicBlock *BB; // The current basic block we are compiling
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unsigned CurReg;
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std::map<Value*, unsigned> RegMap; // Mapping between Val's and SSA Regs
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ISel(MFunction *f)
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: F(f), BB(0), CurReg(MRegisterInfo::FirstVirtualRegister) {}
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/// runOnFunction - Top level implementation of instruction selection for
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/// the entire function.
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///
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bool runOnFunction(Function &F) {
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visit(F);
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RegMap.clear();
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return false; // We never modify the LLVM itself.
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}
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/// visitBasicBlock - This method is called when we are visiting a new basic
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/// block. This simply creates a new MBasicBlock to emit code into and adds
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/// it to the current MFunction. Subsequent visit* for instructions will be
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/// invoked for all instructions in the basic block.
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///
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void visitBasicBlock(BasicBlock &LLVM_BB) {
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BB = new MBasicBlock();
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// FIXME: Use the auto-insert form when it's available
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F->getBasicBlockList().push_back(BB);
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}
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// Visitation methods for various instructions. These methods simply emit
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// fixed X86 code for each instruction.
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//
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void visitReturnInst(ReturnInst &RI);
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void visitAdd(BinaryOperator &B);
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void visitInstruction(Instruction &I) {
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std::cerr << "Cannot instruction select: " << I;
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abort();
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}
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/// copyConstantToRegister - Output the instructions required to put the
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/// specified constant into the specified register.
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///
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void copyConstantToRegister(Constant *C, unsigned Reg);
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/// getReg - This method turns an LLVM value into a register number. This
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/// is guaranteed to produce the same register number for a particular value
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/// every time it is queried.
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///
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unsigned getReg(Value &V) { return getReg(&V); } // Allow references
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unsigned getReg(Value *V) {
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unsigned &Reg = RegMap[V];
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if (Reg == 0)
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Reg = CurReg++;
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// If this operand is a constant, emit the code to copy the constant into
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// the register here...
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//
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if (Constant *C = dyn_cast<Constant>(V))
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copyConstantToRegister(C, Reg);
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return Reg;
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}
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};
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}
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/// copyConstantToRegister - Output the instructions required to put the
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/// specified constant into the specified register.
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///
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void ISel::copyConstantToRegister(Constant *C, unsigned R) {
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assert (!isa<ConstantExpr>(C) && "Constant expressions not yet handled!\n");
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switch (C->getType()->getPrimitiveID()) {
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case Type::SByteTyID:
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BuildMInst(BB, X86::MOVir8, R).addSImm(cast<ConstantSInt>(C)->getValue());
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break;
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case Type::UByteTyID:
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BuildMInst(BB, X86::MOVir8, R).addZImm(cast<ConstantUInt>(C)->getValue());
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break;
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case Type::ShortTyID:
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BuildMInst(BB, X86::MOVir16, R).addSImm(cast<ConstantSInt>(C)->getValue());
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break;
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case Type::UShortTyID:
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BuildMInst(BB, X86::MOVir16, R).addZImm(cast<ConstantUInt>(C)->getValue());
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break;
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case Type::IntTyID:
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BuildMInst(BB, X86::MOVir32, R).addSImm(cast<ConstantSInt>(C)->getValue());
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break;
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case Type::UIntTyID:
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BuildMInst(BB, X86::MOVir32, R).addZImm(cast<ConstantUInt>(C)->getValue());
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break;
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default: assert(0 && "Type not handled yet!");
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}
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}
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/// 'ret' instruction - Here we are interested in meeting the x86 ABI. As such,
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/// we have the following possibilities:
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///
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/// ret void: No return value, simply emit a 'ret' instruction
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/// ret sbyte, ubyte : Extend value into EAX and return
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/// ret short, ushort: Extend value into EAX and return
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/// ret int, uint : Move value into EAX and return
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/// ret pointer : Move value into EAX and return
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/// ret long, ulong : Move value into EAX/EDX (?) and return
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/// ret float/double : ? Top of FP stack? XMM0?
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///
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void ISel::visitReturnInst(ReturnInst &I) {
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if (I.getNumOperands() != 0) { // Not 'ret void'?
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// Move result into a hard register... then emit a ret
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visitInstruction(I); // abort
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}
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// Emit a simple 'ret' instruction... appending it to the end of the basic
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// block
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new MInstruction(BB, X86::RET);
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}
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/// 'add' instruction - Simply turn this into an x86 reg,reg add instruction.
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void ISel::visitAdd(BinaryOperator &B) {
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unsigned Op0r = getReg(B.getOperand(0)), Op1r = getReg(B.getOperand(1));
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unsigned DestReg = getReg(B);
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switch (B.getType()->getPrimitiveSize()) {
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case 1: // UByte, SByte
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BuildMInst(BB, X86::ADDrr8, DestReg).addReg(Op0r).addReg(Op1r);
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break;
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case 2: // UShort, Short
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BuildMInst(BB, X86::ADDrr16, DestReg).addReg(Op0r).addReg(Op1r);
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break;
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case 4: // UInt, Int
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BuildMInst(BB, X86::ADDrr32, DestReg).addReg(Op0r).addReg(Op1r);
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break;
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case 8: // ULong, Long
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default:
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visitInstruction(B); // abort
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}
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}
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/// X86SimpleInstructionSelection - This function converts an LLVM function into
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/// a machine code representation is a very simple peep-hole fashion. The
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/// generated code sucks but the implementation is nice and simple.
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///
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MFunction *X86SimpleInstructionSelection(Function &F) {
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MFunction *Result = new MFunction();
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ISel(Result).runOnFunction(F);
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return Result;
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}
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