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Implement the convertToThreeAddress method, add support for inverting JP/JNP

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llvm-svn: 19247
This commit is contained in:
Chris Lattner 2005-01-02 02:37:07 +00:00
parent 0d6f03e52b
commit d6bc921fa8
2 changed files with 93 additions and 0 deletions
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81
lib/Target/X86/X86InstrInfo.cpp
View File

@ -13,6 +13,7 @@
#include "X86InstrInfo.h"
#include "X86.h"
#include "X86InstrBuilder.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "X86GenInstrInfo.inc"
using namespace llvm;
@ -39,6 +40,83 @@ bool X86InstrInfo::isMoveInstr(const MachineInstr& MI,
return false;
}
/// convertToThreeAddress - This method must be implemented by targets that
/// set the M_CONVERTIBLE_TO_3_ADDR flag. When this flag is set, the target
/// may be able to convert a two-address instruction into a true
/// three-address instruction on demand. This allows the X86 target (for
/// example) to convert ADD and SHL instructions into LEA instructions if they
/// would require register copies due to two-addressness.
///
/// This method returns a null pointer if the transformation cannot be
/// performed, otherwise it returns the new instruction.
///
MachineInstr *X86InstrInfo::convertToThreeAddress(MachineInstr *MI) const {
// All instructions input are two-addr instructions. Get the known operands.
unsigned Dest = MI->getOperand(0).getReg();
unsigned Src = MI->getOperand(1).getReg();
// FIXME: 16-bit LEA's are really slow on Athlons, but not bad on P4's. When
// we have subtarget support, enable the 16-bit LEA generation here.
bool DisableLEA16 = true;
switch (MI->getOpcode()) {
case X86::INC32r:
assert(MI->getNumOperands() == 2 && "Unknown inc instruction!");
return addRegOffset(BuildMI(X86::LEA32r, 5, Dest), Src, 1);
case X86::INC16r:
if (DisableLEA16) return 0;
assert(MI->getNumOperands() == 2 && "Unknown inc instruction!");
return addRegOffset(BuildMI(X86::LEA16r, 5, Dest), Src, 1);
case X86::DEC32r:
assert(MI->getNumOperands() == 2 && "Unknown dec instruction!");
return addRegOffset(BuildMI(X86::LEA32r, 5, Dest), Src, -1);
case X86::DEC16r:
if (DisableLEA16) return 0;
assert(MI->getNumOperands() == 2 && "Unknown dec instruction!");
return addRegOffset(BuildMI(X86::LEA16r, 5, Dest), Src, -1);
case X86::ADD32rr:
assert(MI->getNumOperands() == 3 && "Unknown add instruction!");
return addRegReg(BuildMI(X86::LEA32r, 5, Dest), Src,
MI->getOperand(2).getReg());
case X86::ADD16rr:
if (DisableLEA16) return 0;
assert(MI->getNumOperands() == 3 && "Unknown add instruction!");
return addRegReg(BuildMI(X86::LEA16r, 5, Dest), Src,
MI->getOperand(2).getReg());
case X86::ADD32ri:
assert(MI->getNumOperands() == 3 && "Unknown add instruction!");
if (MI->getOperand(2).isImmediate())
return addRegOffset(BuildMI(X86::LEA32r, 5, Dest), Src,
MI->getOperand(2).getImmedValue());
return 0;
case X86::ADD16ri:
if (DisableLEA16) return 0;
assert(MI->getNumOperands() == 3 && "Unknown add instruction!");
if (MI->getOperand(2).isImmediate())
return addRegOffset(BuildMI(X86::LEA16r, 5, Dest), Src,
MI->getOperand(2).getImmedValue());
break;
case X86::SHL16ri:
if (DisableLEA16) return 0;
case X86::SHL32ri:
assert(MI->getNumOperands() == 3 && MI->getOperand(2).isImmediate() &&
"Unknown shl instruction!");
unsigned ShAmt = MI->getOperand(2).getImmedValue();
if (ShAmt == 1 || ShAmt == 2 || ShAmt == 3) {
X86AddressMode AM;
AM.Scale = 1 << ShAmt;
AM.IndexReg = Src;
unsigned Opc = MI->getOpcode() == X86::SHL32ri ? X86::LEA32r :X86::LEA16r;
return addFullAddress(BuildMI(Opc, 5, Dest), AM);
}
break;
}
return 0;
}
void X86InstrInfo::insertGoto(MachineBasicBlock& MBB,
MachineBasicBlock& TMBB) const {
BuildMI(MBB, MBB.end(), X86::JMP, 1).addMBB(&TMBB);
@ -59,6 +137,8 @@ X86InstrInfo::reverseBranchCondition(MachineBasicBlock::iterator MI) const {
case X86::JA: ROpcode = X86::JBE; break;
case X86::JS: ROpcode = X86::JNS; break;
case X86::JNS: ROpcode = X86::JS; break;
case X86::JP: ROpcode = X86::JNP; break;
case X86::JNP: ROpcode = X86::JP; break;
case X86::JL: ROpcode = X86::JGE; break;
case X86::JGE: ROpcode = X86::JL; break;
case X86::JLE: ROpcode = X86::JG; break;
@ -68,3 +148,4 @@ X86InstrInfo::reverseBranchCondition(MachineBasicBlock::iterator MI) const {
MachineBasicBlock* TMBB = MI->getOperand(0).getMachineBasicBlock();
return BuildMI(*MBB, MBB->erase(MI), ROpcode, 1).addMBB(TMBB);
}

12
lib/Target/X86/X86InstrInfo.h
View File

@ -179,6 +179,18 @@ public:
unsigned& sourceReg,
unsigned& destReg) const;
/// convertToThreeAddress - This method must be implemented by targets that
/// set the M_CONVERTIBLE_TO_3_ADDR flag. When this flag is set, the target
/// may be able to convert a two-address instruction into a true
/// three-address instruction on demand. This allows the X86 target (for
/// example) to convert ADD and SHL instructions into LEA instructions if they
/// would require register copies due to two-addressness.
///
/// This method returns a null pointer if the transformation cannot be
/// performed, otherwise it returns the new instruction.
///
virtual MachineInstr *convertToThreeAddress(MachineInstr *TA) const;
/// Insert a goto (unconditional branch) sequence to TMBB, at the
/// end of MBB
virtual void insertGoto(MachineBasicBlock& MBB,