diff options
Diffstat (limited to 'llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp')
| -rw-r--r-- | llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp b/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp index a8853609a7c8..82c150b988ab 100644 --- a/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp +++ b/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp @@ -21,6 +21,7 @@ #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/RegisterScavenging.h" #include "llvm/MC/MCContext.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" @@ -46,6 +47,10 @@ static cl::opt<bool> RunPreEmitPeephole("ppc-late-peephole", cl::Hidden, cl::init(true), cl::desc("Run pre-emit peephole optimizations.")); +static cl::opt<uint64_t> +DSCRValue("ppc-set-dscr", cl::Hidden, + cl::desc("Set the Data Stream Control Register.")); + namespace { static bool hasPCRelativeForm(MachineInstr &Use) { @@ -407,6 +412,38 @@ static bool hasPCRelativeForm(MachineInstr &Use) { } bool runOnMachineFunction(MachineFunction &MF) override { + // If the user wants to set the DSCR using command-line options, + // load in the specified value at the start of main. + if (DSCRValue.getNumOccurrences() > 0 && MF.getName().equals("main") && + MF.getFunction().hasExternalLinkage()) { + DSCRValue = (uint32_t)(DSCRValue & 0x01FFFFFF); // 25-bit DSCR mask + RegScavenger RS; + MachineBasicBlock &MBB = MF.front(); + // Find an unused GPR according to register liveness + RS.enterBasicBlock(MBB); + unsigned InDSCR = RS.FindUnusedReg(&PPC::GPRCRegClass); + if (InDSCR) { + const PPCInstrInfo *TII = + MF.getSubtarget<PPCSubtarget>().getInstrInfo(); + DebugLoc dl; + MachineBasicBlock::iterator IP = MBB.begin(); // Insert Point + // Copy the 32-bit DSCRValue integer into the GPR InDSCR using LIS and + // ORI, then move to DSCR. If the requested DSCR value is contained + // in a 16-bit signed number, we can emit a single `LI`, but the + // impact of saving one instruction in one function does not warrant + // any additional complexity in the logic here. + BuildMI(MBB, IP, dl, TII->get(PPC::LIS), InDSCR) + .addImm(DSCRValue >> 16); + BuildMI(MBB, IP, dl, TII->get(PPC::ORI), InDSCR) + .addReg(InDSCR) + .addImm(DSCRValue & 0xFFFF); + BuildMI(MBB, IP, dl, TII->get(PPC::MTUDSCR)) + .addReg(InDSCR, RegState::Kill); + } else + errs() << "Warning: Ran out of registers - Unable to set DSCR as " + "requested"; + } + if (skipFunction(MF.getFunction()) || !RunPreEmitPeephole) { // Remove UNENCODED_NOP even when this pass is disabled. // This needs to be done unconditionally so we don't emit zeros |