typedef DenseMap<MachineInstr *, CallContext> ContextMap;
bool isLegal(MachineFunction &MF);
-
+
bool isProfitable(MachineFunction &MF, ContextMap &CallSeqMap);
void collectCallInfo(MachineFunction &MF, MachineBasicBlock &MBB,
MachineInstr *canFoldIntoRegPush(MachineBasicBlock::iterator FrameSetup,
unsigned Reg);
+ enum InstClassification { Convert, Skip, Exit };
+
+ InstClassification classifyInstruction(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator MI,
+ const X86RegisterInfo &RegInfo,
+ DenseSet<unsigned int> &UsedRegs);
+
const char *getPassName() const override { return "X86 Optimize Call Frame"; }
const TargetInstrInfo *TII;
return new X86CallFrameOptimization();
}
-// This checks whether the transformation is legal.
+// This checks whether the transformation is legal.
// Also returns false in cases where it's potentially legal, but
// we don't even want to try.
bool X86CallFrameOptimization::isLegal(MachineFunction &MF) {
if (!OptForSize)
return false;
-
unsigned StackAlign = TFL->getStackAlignment();
-
+
int64_t Advantage = 0;
for (auto CC : CallSeqMap) {
// Call sites where no parameters are passed on the stack
return (Advantage >= 0);
}
-
bool X86CallFrameOptimization::runOnMachineFunction(MachineFunction &MF) {
TII = MF.getSubtarget().getInstrInfo();
TFL = MF.getSubtarget().getFrameLowering();
return Changed;
}
+X86CallFrameOptimization::InstClassification
+X86CallFrameOptimization::classifyInstruction(
+ MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+ const X86RegisterInfo &RegInfo, DenseSet<unsigned int> &UsedRegs) {
+ if (MI == MBB.end())
+ return Exit;
+
+ // The instructions we actually care about are movs onto the stack
+ int Opcode = MI->getOpcode();
+ if (Opcode == X86::MOV32mi || Opcode == X86::MOV32mr)
+ return Convert;
+
+ // Not all calling conventions have only stack MOVs between the stack
+ // adjust and the call.
+
+ // We want to tolerate other instructions, to cover more cases.
+ // In particular:
+ // a) PCrel calls, where we expect an additional COPY of the basereg.
+ // b) Passing frame-index addresses.
+ // c) Calling conventions that have inreg parameters. These generate
+ // both copies and movs into registers.
+ // To avoid creating lots of special cases, allow any instruction
+ // that does not write into memory, does not def or use the stack
+ // pointer, and does not def any register that was used by a preceding
+ // push.
+ // (Reading from memory is allowed, even if referenced through a
+ // frame index, since these will get adjusted properly in PEI)
+
+ // The reason for the last condition is that the pushes can't replace
+ // the movs in place, because the order must be reversed.
+ // So if we have a MOV32mr that uses EDX, then an instruction that defs
+ // EDX, and then the call, after the transformation the push will use
+ // the modified version of EDX, and not the original one.
+ // Since we are still in SSA form at this point, we only need to
+ // make sure we don't clobber any *physical* registers that were
+ // used by an earlier mov that will become a push.
+
+ if (MI->isCall() || MI->mayStore())
+ return Exit;
+
+ for (const MachineOperand &MO : MI->operands()) {
+ if (!MO.isReg())
+ continue;
+ unsigned int Reg = MO.getReg();
+ if (!RegInfo.isPhysicalRegister(Reg))
+ continue;
+ if (RegInfo.regsOverlap(Reg, RegInfo.getStackRegister()))
+ return Exit;
+ if (MO.isDef()) {
+ for (unsigned int U : UsedRegs)
+ if (RegInfo.regsOverlap(Reg, U))
+ return Exit;
+ }
+ }
+
+ return Skip;
+}
+
void X86CallFrameOptimization::collectCallInfo(MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
// How much do we adjust the stack? This puts an upper bound on
// the number of parameters actually passed on it.
- unsigned int MaxAdjust = FrameSetup->getOperand(0).getImm() / 4;
-
+ unsigned int MaxAdjust = FrameSetup->getOperand(0).getImm() / 4;
+
// A zero adjustment means no stack parameters
if (!MaxAdjust) {
Context.NoStackParams = true;
if (MaxAdjust > 4)
Context.MovVector.resize(MaxAdjust, nullptr);
- do {
- int Opcode = I->getOpcode();
- if (Opcode != X86::MOV32mi && Opcode != X86::MOV32mr)
- break;
+ InstClassification Classification;
+ DenseSet<unsigned int> UsedRegs;
+ while ((Classification = classifyInstruction(MBB, I, RegInfo, UsedRegs)) !=
+ Exit) {
+ if (Classification == Skip) {
+ ++I;
+ continue;
+ }
+
+ // We know the instruction is a MOV32mi/MOV32mr.
// We only want movs of the form:
// movl imm/r32, k(%esp)
// If we run into something else, bail.
return;
Context.MovVector[StackDisp] = I;
- ++I;
- } while (I != MBB.end());
-
- // We now expect the end of the sequence - a call and a stack adjust.
- if (I == MBB.end())
- return;
+ for (const MachineOperand &MO : I->uses()) {
+ if (!MO.isReg())
+ continue;
+ unsigned int Reg = MO.getReg();
+ if (RegInfo.isPhysicalRegister(Reg))
+ UsedRegs.insert(Reg);
+ }
- // For PCrel calls, we expect an additional COPY of the basereg.
- // If we find one, skip it.
- if (I->isCopy()) {
- if (I->getOperand(1).getReg() ==
- MF.getInfo<X86MachineFunctionInfo>()->getGlobalBaseReg())
- ++I;
- else
- return;
+ ++I;
}
- if (!I->isCall())
+ // We now expect the end of the sequence. If we stopped early,
+ // or reached the end of the block without finding a call, bail.
+ if (I == MBB.end() || !I->isCall())
return;
Context.Call = I;
projects / oota-llvm.git / blobdiff