forked from OSchip/llvm-project
If we have a load of a global address that's not modified during the
function, then go ahead and hoist it out of the loop. This is the result: $ cat a.c volatile int G; int A(int N) { for (; N > 0; --N) G++; } $ llc -o - -relocation-model=pic _A: ... LBB1_2: # bb movl L_G$non_lazy_ptr-"L1$pb"(%eax), %esi incl (%esi) incl %edx cmpl %ecx, %edx jne LBB1_2 # bb ... $ llc -o - -relocation-model=pic -machine-licm _A: ... movl L_G$non_lazy_ptr-"L1$pb"(%eax), %eax LBB1_2: # bb incl (%eax) incl %edx cmpl %ecx, %edx jne LBB1_2 # bb ... I'm limiting this to the MOV32rm x86 instruction for now. llvm-svn: 45444
This commit is contained in:
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@ -144,6 +144,37 @@ bool X86InstrInfo::isReallyTriviallyReMaterializable(MachineInstr *MI) const {
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return true;
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return true;
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}
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}
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/// isDefinedInEntryBlock - Goes through the entry block to see if the given
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/// virtual register is indeed defined in the entry block.
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///
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bool X86InstrInfo::isDefinedInEntryBlock(const MachineBasicBlock &Entry,
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unsigned VReg) const {
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assert(MRegisterInfo::isVirtualRegister(VReg) &&
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"Map only holds virtual registers!");
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MachineInstrMap.grow(VReg);
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if (MachineInstrMap[VReg]) return true;
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MachineBasicBlock::const_iterator I = Entry.begin(), E = Entry.end();
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for (; I != E; ++I) {
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const MachineInstr &MI = *I;
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unsigned NumOps = MI.getNumOperands();
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for (unsigned i = 0; i < NumOps; ++i) {
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const MachineOperand &MO = MI.getOperand(i);
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if(MO.isRegister() && MO.isDef() &&
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MRegisterInfo::isVirtualRegister(MO.getReg()) &&
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MO.getReg() == VReg) {
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MachineInstrMap[VReg] = &MI;
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return true;
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}
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}
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}
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return false;
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}
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/// isReallySideEffectFree - If the M_MAY_HAVE_SIDE_EFFECTS flag is set, this
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/// isReallySideEffectFree - If the M_MAY_HAVE_SIDE_EFFECTS flag is set, this
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/// method is called to determine if the specific instance of this instruction
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/// method is called to determine if the specific instance of this instruction
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/// has side effects. This is useful in cases of instructions, like loads, which
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/// has side effects. This is useful in cases of instructions, like loads, which
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@ -152,10 +183,25 @@ bool X86InstrInfo::isReallyTriviallyReMaterializable(MachineInstr *MI) const {
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bool X86InstrInfo::isReallySideEffectFree(MachineInstr *MI) const {
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bool X86InstrInfo::isReallySideEffectFree(MachineInstr *MI) const {
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switch (MI->getOpcode()) {
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switch (MI->getOpcode()) {
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default: break;
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default: break;
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case X86::MOV32rm:
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if (MI->getOperand(1).isRegister()) {
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unsigned Reg = MI->getOperand(1).getReg();
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// Loads from global addresses which aren't redefined in the function are
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// side effect free.
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if (MRegisterInfo::isVirtualRegister(Reg) &&
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isDefinedInEntryBlock(MI->getParent()->getParent()->front(), Reg) &&
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MI->getOperand(2).isImmediate() &&
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MI->getOperand(3).isRegister() &&
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MI->getOperand(4).isGlobalAddress() &&
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MI->getOperand(2).getImmedValue() == 1 &&
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MI->getOperand(3).getReg() == 0)
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return true;
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}
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// FALLTHROUGH
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case X86::MOV8rm:
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case X86::MOV8rm:
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case X86::MOV16rm:
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case X86::MOV16rm:
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case X86::MOV16_rm:
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case X86::MOV16_rm:
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case X86::MOV32rm:
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case X86::MOV32_rm:
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case X86::MOV32_rm:
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case X86::MOV64rm:
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case X86::MOV64rm:
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case X86::LD_Fp64m:
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case X86::LD_Fp64m:
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@ -166,8 +212,10 @@ bool X86InstrInfo::isReallySideEffectFree(MachineInstr *MI) const {
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case X86::MMX_MOVD64rm:
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case X86::MMX_MOVD64rm:
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case X86::MMX_MOVQ64rm:
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case X86::MMX_MOVQ64rm:
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// Loads from constant pools have no side effects
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// Loads from constant pools have no side effects
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return MI->getOperand(1).isRegister() && MI->getOperand(2).isImmediate() &&
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return MI->getOperand(1).isRegister() &&
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MI->getOperand(3).isRegister() && MI->getOperand(4).isConstantPoolIndex() &&
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MI->getOperand(2).isImmediate() &&
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MI->getOperand(3).isRegister() &&
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MI->getOperand(4).isConstantPoolIndex() &&
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MI->getOperand(1).getReg() == 0 &&
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MI->getOperand(1).getReg() == 0 &&
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MI->getOperand(2).getImmedValue() == 1 &&
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MI->getOperand(2).getImmedValue() == 1 &&
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MI->getOperand(3).getReg() == 0;
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MI->getOperand(3).getReg() == 0;
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@ -16,6 +16,8 @@
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "X86RegisterInfo.h"
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#include "X86RegisterInfo.h"
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#include "llvm/ADT/IndexedMap.h"
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#include "llvm/Target/MRegisterInfo.h"
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namespace llvm {
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namespace llvm {
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class X86RegisterInfo;
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class X86RegisterInfo;
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@ -223,6 +225,13 @@ namespace X86II {
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class X86InstrInfo : public TargetInstrInfo {
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class X86InstrInfo : public TargetInstrInfo {
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X86TargetMachine &TM;
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X86TargetMachine &TM;
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const X86RegisterInfo RI;
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const X86RegisterInfo RI;
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mutable IndexedMap<const MachineInstr*, VirtReg2IndexFunctor> MachineInstrMap;
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/// isDefinedInEntryBlock - Goes through the entry block to see if the given
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/// virtual register is indeed defined in the entry block.
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///
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bool isDefinedInEntryBlock(const MachineBasicBlock &Entry,
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unsigned VReg) const;
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public:
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public:
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X86InstrInfo(X86TargetMachine &tm);
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X86InstrInfo(X86TargetMachine &tm);
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