mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-28 06:29:45 +00:00
Although I had added some support for the BDZ/BDNZ branches into the selector (in r158204), I had not correctly adjusted the condition at the top of the loop. As a result, these branches were still essentially unsupported. This fixes PR16086. Unfortunately, any test case would be very large (because it would need to force the loop backedge to exceed the range of the 16-bit immediate). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182385 91177308-0d34-0410-b5e6-96231b3b80d8
202 lines
6.9 KiB
C++
202 lines
6.9 KiB
C++
//===-- PPCBranchSelector.cpp - Emit long conditional branches ------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file contains a pass that scans a machine function to determine which
|
|
// conditional branches need more than 16 bits of displacement to reach their
|
|
// target basic block. It does this in two passes; a calculation of basic block
|
|
// positions pass, and a branch pseudo op to machine branch opcode pass. This
|
|
// pass should be run last, just before the assembly printer.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "ppc-branch-select"
|
|
#include "PPC.h"
|
|
#include "MCTargetDesc/PPCPredicates.h"
|
|
#include "PPCInstrBuilder.h"
|
|
#include "PPCInstrInfo.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/CodeGen/MachineFunctionPass.h"
|
|
#include "llvm/Support/MathExtras.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumExpanded, "Number of branches expanded to long format");
|
|
|
|
namespace llvm {
|
|
void initializePPCBSelPass(PassRegistry&);
|
|
}
|
|
|
|
namespace {
|
|
struct PPCBSel : public MachineFunctionPass {
|
|
static char ID;
|
|
PPCBSel() : MachineFunctionPass(ID) {
|
|
initializePPCBSelPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
/// BlockSizes - The sizes of the basic blocks in the function.
|
|
std::vector<unsigned> BlockSizes;
|
|
|
|
virtual bool runOnMachineFunction(MachineFunction &Fn);
|
|
|
|
virtual const char *getPassName() const {
|
|
return "PowerPC Branch Selector";
|
|
}
|
|
};
|
|
char PPCBSel::ID = 0;
|
|
}
|
|
|
|
INITIALIZE_PASS(PPCBSel, "ppc-branch-select", "PowerPC Branch Selector",
|
|
false, false)
|
|
|
|
/// createPPCBranchSelectionPass - returns an instance of the Branch Selection
|
|
/// Pass
|
|
///
|
|
FunctionPass *llvm::createPPCBranchSelectionPass() {
|
|
return new PPCBSel();
|
|
}
|
|
|
|
bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
|
const PPCInstrInfo *TII =
|
|
static_cast<const PPCInstrInfo*>(Fn.getTarget().getInstrInfo());
|
|
// Give the blocks of the function a dense, in-order, numbering.
|
|
Fn.RenumberBlocks();
|
|
BlockSizes.resize(Fn.getNumBlockIDs());
|
|
|
|
// Measure each MBB and compute a size for the entire function.
|
|
unsigned FuncSize = 0;
|
|
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
|
|
++MFI) {
|
|
MachineBasicBlock *MBB = MFI;
|
|
|
|
unsigned BlockSize = 0;
|
|
for (MachineBasicBlock::iterator MBBI = MBB->begin(), EE = MBB->end();
|
|
MBBI != EE; ++MBBI)
|
|
BlockSize += TII->GetInstSizeInBytes(MBBI);
|
|
|
|
BlockSizes[MBB->getNumber()] = BlockSize;
|
|
FuncSize += BlockSize;
|
|
}
|
|
|
|
// If the entire function is smaller than the displacement of a branch field,
|
|
// we know we don't need to shrink any branches in this function. This is a
|
|
// common case.
|
|
if (FuncSize < (1 << 15)) {
|
|
BlockSizes.clear();
|
|
return false;
|
|
}
|
|
|
|
// For each conditional branch, if the offset to its destination is larger
|
|
// than the offset field allows, transform it into a long branch sequence
|
|
// like this:
|
|
// short branch:
|
|
// bCC MBB
|
|
// long branch:
|
|
// b!CC $PC+8
|
|
// b MBB
|
|
//
|
|
bool MadeChange = true;
|
|
bool EverMadeChange = false;
|
|
while (MadeChange) {
|
|
// Iteratively expand branches until we reach a fixed point.
|
|
MadeChange = false;
|
|
|
|
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
|
|
++MFI) {
|
|
MachineBasicBlock &MBB = *MFI;
|
|
unsigned MBBStartOffset = 0;
|
|
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
|
|
I != E; ++I) {
|
|
MachineBasicBlock *Dest = 0;
|
|
if (I->getOpcode() == PPC::BCC && !I->getOperand(2).isImm())
|
|
Dest = I->getOperand(2).getMBB();
|
|
else if ((I->getOpcode() == PPC::BDNZ8 || I->getOpcode() == PPC::BDNZ ||
|
|
I->getOpcode() == PPC::BDZ8 || I->getOpcode() == PPC::BDZ) &&
|
|
!I->getOperand(0).isImm())
|
|
Dest = I->getOperand(0).getMBB();
|
|
|
|
if (!Dest) {
|
|
MBBStartOffset += TII->GetInstSizeInBytes(I);
|
|
continue;
|
|
}
|
|
|
|
// Determine the offset from the current branch to the destination
|
|
// block.
|
|
int BranchSize;
|
|
if (Dest->getNumber() <= MBB.getNumber()) {
|
|
// If this is a backwards branch, the delta is the offset from the
|
|
// start of this block to this branch, plus the sizes of all blocks
|
|
// from this block to the dest.
|
|
BranchSize = MBBStartOffset;
|
|
|
|
for (unsigned i = Dest->getNumber(), e = MBB.getNumber(); i != e; ++i)
|
|
BranchSize += BlockSizes[i];
|
|
} else {
|
|
// Otherwise, add the size of the blocks between this block and the
|
|
// dest to the number of bytes left in this block.
|
|
BranchSize = -MBBStartOffset;
|
|
|
|
for (unsigned i = MBB.getNumber(), e = Dest->getNumber(); i != e; ++i)
|
|
BranchSize += BlockSizes[i];
|
|
}
|
|
|
|
// If this branch is in range, ignore it.
|
|
if (isInt<16>(BranchSize)) {
|
|
MBBStartOffset += 4;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, we have to expand it to a long branch.
|
|
MachineInstr *OldBranch = I;
|
|
DebugLoc dl = OldBranch->getDebugLoc();
|
|
|
|
if (I->getOpcode() == PPC::BCC) {
|
|
// The BCC operands are:
|
|
// 0. PPC branch predicate
|
|
// 1. CR register
|
|
// 2. Target MBB
|
|
PPC::Predicate Pred = (PPC::Predicate)I->getOperand(0).getImm();
|
|
unsigned CRReg = I->getOperand(1).getReg();
|
|
|
|
// Jump over the uncond branch inst (i.e. $PC+8) on opposite condition.
|
|
BuildMI(MBB, I, dl, TII->get(PPC::BCC))
|
|
.addImm(PPC::InvertPredicate(Pred)).addReg(CRReg).addImm(2);
|
|
} else if (I->getOpcode() == PPC::BDNZ) {
|
|
BuildMI(MBB, I, dl, TII->get(PPC::BDZ)).addImm(2);
|
|
} else if (I->getOpcode() == PPC::BDNZ8) {
|
|
BuildMI(MBB, I, dl, TII->get(PPC::BDZ8)).addImm(2);
|
|
} else if (I->getOpcode() == PPC::BDZ) {
|
|
BuildMI(MBB, I, dl, TII->get(PPC::BDNZ)).addImm(2);
|
|
} else if (I->getOpcode() == PPC::BDZ8) {
|
|
BuildMI(MBB, I, dl, TII->get(PPC::BDNZ8)).addImm(2);
|
|
} else {
|
|
llvm_unreachable("Unhandled branch type!");
|
|
}
|
|
|
|
// Uncond branch to the real destination.
|
|
I = BuildMI(MBB, I, dl, TII->get(PPC::B)).addMBB(Dest);
|
|
|
|
// Remove the old branch from the function.
|
|
OldBranch->eraseFromParent();
|
|
|
|
// Remember that this instruction is 8-bytes, increase the size of the
|
|
// block by 4, remember to iterate.
|
|
BlockSizes[MBB.getNumber()] += 4;
|
|
MBBStartOffset += 8;
|
|
++NumExpanded;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
EverMadeChange |= MadeChange;
|
|
}
|
|
|
|
BlockSizes.clear();
|
|
return true;
|
|
}
|
|
|