// License. See LICENSE.TXT for details.
//
// The loop start address in the LOOPn instruction is encoded as a distance
-// from the LOOPn instruction itself. If the start address is too far from
-// the LOOPn instruction, the loop needs to be set up manually, i.e. via
-// direct transfers to SAn and LCn.
+// from the LOOPn instruction itself. If the start address is too far from
+// the LOOPn instruction, the instruction needs to use a constant extender.
// This pass will identify and convert such LOOPn instructions to a proper
// form.
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/PassSupport.h"
#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
+static cl::opt<unsigned> MaxLoopRange(
+ "hexagon-loop-range", cl::Hidden, cl::init(200),
+ cl::desc("Restrict range of loopN instructions (testing only)"));
+
namespace llvm {
void initializeHexagonFixupHwLoopsPass(PassRegistry&);
}
}
private:
- /// \brief Maximum distance between the loop instr and the basic block.
- /// Just an estimate.
- static const unsigned MAX_LOOP_DISTANCE = 200;
-
/// \brief Check the offset between each loop instruction and
/// the loop basic block to determine if we can use the LOOP instruction
/// or if we need to set the LC/SA registers explicitly.
bool fixupLoopInstrs(MachineFunction &MF);
- /// \brief Add the instruction to set the LC and SA registers explicitly.
- void convertLoopInstr(MachineFunction &MF,
- MachineBasicBlock::iterator &MII,
- RegScavenger &RS);
-
+ /// \brief Replace loop instruction with the constant extended
+ /// version if the loop label is too far from the loop instruction.
+ void useExtLoopInstr(MachineFunction &MF,
+ MachineBasicBlock::iterator &MII);
};
char HexagonFixupHwLoops::ID = 0;
return new HexagonFixupHwLoops();
}
-
/// \brief Returns true if the instruction is a hardware loop instruction.
static bool isHardwareLoop(const MachineInstr *MI) {
return MI->getOpcode() == Hexagon::J2_loop0r ||
- MI->getOpcode() == Hexagon::J2_loop0i;
+ MI->getOpcode() == Hexagon::J2_loop0i ||
+ MI->getOpcode() == Hexagon::J2_loop1r ||
+ MI->getOpcode() == Hexagon::J2_loop1i;
}
-
bool HexagonFixupHwLoops::runOnMachineFunction(MachineFunction &MF) {
- bool Changed = fixupLoopInstrs(MF);
- return Changed;
+ return fixupLoopInstrs(MF);
}
-
/// \brief For Hexagon, if the loop label is to far from the
/// loop instruction then we need to set the LC0 and SA0 registers
/// explicitly instead of using LOOP(start,count). This function
// Offset of the current instruction from the start.
unsigned InstOffset = 0;
// Map for each basic block to it's first instruction.
- DenseMap<MachineBasicBlock*, unsigned> BlockToInstOffset;
+ DenseMap<const MachineBasicBlock *, unsigned> BlockToInstOffset;
+
+ const HexagonInstrInfo *HII =
+ static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo());
// First pass - compute the offset of each basic block.
- for (MachineFunction::iterator MBB = MF.begin(), MBBe = MF.end();
- MBB != MBBe; ++MBB) {
- BlockToInstOffset[MBB] = InstOffset;
- InstOffset += (MBB->size() * 4);
+ for (const MachineBasicBlock &MBB : MF) {
+ if (MBB.getAlignment()) {
+ // Although we don't know the exact layout of the final code, we need
+ // to account for alignment padding somehow. This heuristic pads each
+ // aligned basic block according to the alignment value.
+ int ByteAlign = (1u << MBB.getAlignment()) - 1;
+ InstOffset = (InstOffset + ByteAlign) & ~(ByteAlign);
+ }
+
+ BlockToInstOffset[&MBB] = InstOffset;
+ for (const MachineInstr &MI : MBB)
+ InstOffset += HII->getSize(&MI);
}
- // Second pass - check each loop instruction to see if it needs to
- // be converted.
+ // Second pass - check each loop instruction to see if it needs to be
+ // converted.
InstOffset = 0;
bool Changed = false;
- RegScavenger RS;
-
- // Loop over all the basic blocks.
- for (MachineFunction::iterator MBB = MF.begin(), MBBe = MF.end();
- MBB != MBBe; ++MBB) {
- InstOffset = BlockToInstOffset[MBB];
- RS.enterBasicBlock(MBB);
+ for (MachineBasicBlock &MBB : MF) {
+ InstOffset = BlockToInstOffset[&MBB];
// Loop over all the instructions.
- MachineBasicBlock::iterator MIE = MBB->end();
- MachineBasicBlock::iterator MII = MBB->begin();
+ MachineBasicBlock::iterator MII = MBB.begin();
+ MachineBasicBlock::iterator MIE = MBB.end();
while (MII != MIE) {
+ InstOffset += HII->getSize(&*MII);
+ if (MII->isDebugValue()) {
+ ++MII;
+ continue;
+ }
if (isHardwareLoop(MII)) {
- RS.forward(MII);
assert(MII->getOperand(0).isMBB() &&
"Expect a basic block as loop operand");
- int Sub = InstOffset - BlockToInstOffset[MII->getOperand(0).getMBB()];
- unsigned Dist = Sub > 0 ? Sub : -Sub;
- if (Dist > MAX_LOOP_DISTANCE) {
- // Convert to explicity setting LC0 and SA0.
- convertLoopInstr(MF, MII, RS);
- MII = MBB->erase(MII);
+ int diff = InstOffset - BlockToInstOffset[MII->getOperand(0).getMBB()];
+ if ((unsigned)abs(diff) > MaxLoopRange) {
+ useExtLoopInstr(MF, MII);
+ MII = MBB.erase(MII);
Changed = true;
} else {
++MII;
} else {
++MII;
}
- InstOffset += 4;
}
}
return Changed;
}
-
-/// \brief convert a loop instruction to a sequence of instructions that
-/// set the LC0 and SA0 register explicitly.
-void HexagonFixupHwLoops::convertLoopInstr(MachineFunction &MF,
- MachineBasicBlock::iterator &MII,
- RegScavenger &RS) {
+/// \brief Replace loop instructions with the constant extended version.
+void HexagonFixupHwLoops::useExtLoopInstr(MachineFunction &MF,
+ MachineBasicBlock::iterator &MII) {
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
MachineBasicBlock *MBB = MII->getParent();
DebugLoc DL = MII->getDebugLoc();
- unsigned Scratch = RS.scavengeRegister(&Hexagon::IntRegsRegClass, MII, 0);
-
- // First, set the LC0 with the trip count.
- if (MII->getOperand(1).isReg()) {
- // Trip count is a register
- BuildMI(*MBB, MII, DL, TII->get(Hexagon::A2_tfrrcr), Hexagon::LC0)
- .addReg(MII->getOperand(1).getReg());
- } else {
- // Trip count is an immediate.
- BuildMI(*MBB, MII, DL, TII->get(Hexagon::A2_tfrsi), Scratch)
- .addImm(MII->getOperand(1).getImm());
- BuildMI(*MBB, MII, DL, TII->get(Hexagon::A2_tfrrcr), Hexagon::LC0)
- .addReg(Scratch);
+ MachineInstrBuilder MIB;
+ unsigned newOp;
+ switch (MII->getOpcode()) {
+ case Hexagon::J2_loop0r:
+ newOp = Hexagon::J2_loop0rext;
+ break;
+ case Hexagon::J2_loop0i:
+ newOp = Hexagon::J2_loop0iext;
+ break;
+ case Hexagon::J2_loop1r:
+ newOp = Hexagon::J2_loop1rext;
+ break;
+ case Hexagon::J2_loop1i:
+ newOp = Hexagon::J2_loop1iext;
+ break;
+ default:
+ llvm_unreachable("Invalid Hardware Loop Instruction.");
}
- // Then, set the SA0 with the loop start address.
- BuildMI(*MBB, MII, DL, TII->get(Hexagon::A2_tfrsi), Scratch)
- .addMBB(MII->getOperand(0).getMBB());
- BuildMI(*MBB, MII, DL, TII->get(Hexagon::A2_tfrrcr), Hexagon::SA0)
- .addReg(Scratch);
+ MIB = BuildMI(*MBB, MII, DL, TII->get(newOp));
+
+ for (unsigned i = 0; i < MII->getNumOperands(); ++i)
+ MIB.addOperand(MII->getOperand(i));
}
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