#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetOptions.h"
+#include "llvm/ADT/Statistic.h"
#include <limits>
#define GET_INSTRINFO_CTOR
using namespace llvm;
+STATISTIC(NumCmpsRemoved, "Number of Cmps removed due to an earlier Sub");
+
static cl::opt<bool>
NoFusing("disable-spill-fusing",
cl::desc("Disable fusing of spill code into instructions"));
NewMIs.push_back(MIB);
}
+bool X86InstrInfo::
+AnalyzeCompare(const MachineInstr *MI, unsigned &SrcReg, int &CmpMask,
+ int &CmpValue) const {
+ switch (MI->getOpcode()) {
+ default: break;
+ case X86::CMP64ri32:
+ case X86::CMP64ri8:
+ case X86::CMP32ri:
+ case X86::CMP32ri8:
+ case X86::CMP16ri:
+ case X86::CMP16ri8:
+ case X86::CMP8ri:
+ SrcReg = MI->getOperand(0).getReg();
+ CmpMask = ~0;
+ CmpValue = MI->getOperand(1).getImm();
+ return true;
+ case X86::CMP64rr:
+ case X86::CMP32rr:
+ case X86::CMP16rr:
+ case X86::CMP8rr:
+ SrcReg = MI->getOperand(0).getReg();
+ CmpMask = ~0;
+ CmpValue = 0;
+ return true;
+ }
+
+ return false;
+}
+
+// This function updates condition code for SET Opcodes.
+// The input condition code can be E,NE,L,LE,G,GE,B,BE,A,AE and
+// the updated condition code will be E,NE,G,GE,L,LE,A,AE,B,BE.
+// This is to convert from a > b to b < a, a >= b to b <= a etc.
+static unsigned UpdateSETCondToOptimizeCmp(unsigned SETOpc) {
+ switch (SETOpc) {
+ default: return 0;
+ case X86::SETEr: return X86::SETEr;
+ case X86::SETEm: return X86::SETEm;
+ case X86::SETNEr: return X86::SETNEr;
+ case X86::SETNEm: return X86::SETNEm;
+ case X86::SETLr: return X86::SETGr;
+ case X86::SETLm: return X86::SETGm;
+ case X86::SETLEr: return X86::SETGEr;
+ case X86::SETLEm: return X86::SETGEm;
+ case X86::SETGr: return X86::SETLr;
+ case X86::SETGm: return X86::SETLm;
+ case X86::SETGEr: return X86::SETLEr;
+ case X86::SETGEm: return X86::SETLEm;
+ case X86::SETBr: return X86::SETAr;
+ case X86::SETBm: return X86::SETAm;
+ case X86::SETBEr: return X86::SETAEr;
+ case X86::SETBEm: return X86::SETAEm;
+ case X86::SETAr: return X86::SETBr;
+ case X86::SETAm: return X86::SETBm;
+ case X86::SETAEr: return X86::SETBEr;
+ case X86::SETAEm: return X86::SETBEm;
+ }
+}
+
+// This function updates condition code for Branch Opcodes.
+// The input condition code can be E,NE,L,LE,G,GE,B,BE,A,AE and
+// the updated condition code will be E,NE,G,GE,L,LE,A,AE,B,BE.
+// This is to convert from a > b to b < a, a >= b to b <= a etc.
+static unsigned UpdateBranchCondToOptimizeCmp(unsigned BranchOpc) {
+ switch (BranchOpc) {
+ default: return 0;
+ case X86::JE_4: return X86::JE_4;
+ case X86::JNE_4: return X86::JNE_4;
+ case X86::JL_4: return X86::JG_4;
+ case X86::JLE_4: return X86::JGE_4;
+ case X86::JG_4: return X86::JL_4;
+ case X86::JGE_4: return X86::JLE_4;
+ case X86::JB_4: return X86::JA_4;
+ case X86::JBE_4: return X86::JAE_4;
+ case X86::JA_4: return X86::JB_4;
+ case X86::JAE_4: return X86::JBE_4;
+ }
+}
+
+// This function updates condition code for CMOV Opcodes.
+// The input condition code can be E,NE,L,LE,G,GE,B,BE,A,AE and
+// the updated condition code will be E,NE,G,GE,L,LE,A,AE,B,BE.
+// This is to convert from a > b to b < a, a >= b to b <= a etc.
+static unsigned UpdateCMovCondToOptimizeCmp(unsigned CMovOpc) {
+ switch (CMovOpc) {
+ default: return 0;
+ case X86::CMOVE16rm: return X86::CMOVE16rm;
+ case X86::CMOVE16rr: return X86::CMOVE16rr;
+ case X86::CMOVE32rm: return X86::CMOVE32rm;
+ case X86::CMOVE32rr: return X86::CMOVE32rr;
+ case X86::CMOVE64rm: return X86::CMOVE64rm;
+ case X86::CMOVE64rr: return X86::CMOVE64rr;
+ case X86::CMOVNE16rm: return X86::CMOVNE16rm;
+ case X86::CMOVNE16rr: return X86::CMOVNE16rr;
+ case X86::CMOVNE32rm: return X86::CMOVNE32rm;
+ case X86::CMOVNE32rr: return X86::CMOVNE32rr;
+ case X86::CMOVNE64rm: return X86::CMOVNE64rm;
+ case X86::CMOVNE64rr: return X86::CMOVNE64rr;
+
+ case X86::CMOVL16rm: return X86::CMOVG16rm;
+ case X86::CMOVL16rr: return X86::CMOVG16rr;
+ case X86::CMOVL32rm: return X86::CMOVG32rm;
+ case X86::CMOVL32rr: return X86::CMOVG32rr;
+ case X86::CMOVL64rm: return X86::CMOVG64rm;
+ case X86::CMOVL64rr: return X86::CMOVG64rr;
+ case X86::CMOVLE16rm: return X86::CMOVGE16rm;
+ case X86::CMOVLE16rr: return X86::CMOVGE16rr;
+ case X86::CMOVLE32rm: return X86::CMOVGE32rm;
+ case X86::CMOVLE32rr: return X86::CMOVGE32rr;
+ case X86::CMOVLE64rm: return X86::CMOVGE64rm;
+ case X86::CMOVLE64rr: return X86::CMOVGE64rr;
+
+ case X86::CMOVG16rm: return X86::CMOVL16rm;
+ case X86::CMOVG16rr: return X86::CMOVL16rr;
+ case X86::CMOVG32rm: return X86::CMOVL32rm;
+ case X86::CMOVG32rr: return X86::CMOVL32rr;
+ case X86::CMOVG64rm: return X86::CMOVL64rm;
+ case X86::CMOVG64rr: return X86::CMOVL64rr;
+ case X86::CMOVGE16rm: return X86::CMOVLE16rm;
+ case X86::CMOVGE16rr: return X86::CMOVLE16rr;
+ case X86::CMOVGE32rm: return X86::CMOVLE32rm;
+ case X86::CMOVGE32rr: return X86::CMOVLE32rr;
+ case X86::CMOVGE64rm: return X86::CMOVLE64rm;
+ case X86::CMOVGE64rr: return X86::CMOVLE64rr;
+
+ case X86::CMOVB16rm: return X86::CMOVA16rm;
+ case X86::CMOVB16rr: return X86::CMOVA16rr;
+ case X86::CMOVB32rm: return X86::CMOVA32rm;
+ case X86::CMOVB32rr: return X86::CMOVA32rr;
+ case X86::CMOVB64rm: return X86::CMOVA64rm;
+ case X86::CMOVB64rr: return X86::CMOVA64rr;
+ case X86::CMOVBE16rm: return X86::CMOVAE16rm;
+ case X86::CMOVBE16rr: return X86::CMOVAE16rr;
+ case X86::CMOVBE32rm: return X86::CMOVAE32rm;
+ case X86::CMOVBE32rr: return X86::CMOVAE32rr;
+ case X86::CMOVBE64rm: return X86::CMOVAE64rm;
+ case X86::CMOVBE64rr: return X86::CMOVAE64rr;
+
+ case X86::CMOVA16rm: return X86::CMOVB16rm;
+ case X86::CMOVA16rr: return X86::CMOVB16rr;
+ case X86::CMOVA32rm: return X86::CMOVB32rm;
+ case X86::CMOVA32rr: return X86::CMOVB32rr;
+ case X86::CMOVA64rm: return X86::CMOVB64rm;
+ case X86::CMOVA64rr: return X86::CMOVB64rr;
+ case X86::CMOVAE16rm: return X86::CMOVBE16rm;
+ case X86::CMOVAE16rr: return X86::CMOVBE16rr;
+ case X86::CMOVAE32rm: return X86::CMOVBE32rm;
+ case X86::CMOVAE32rr: return X86::CMOVBE32rr;
+ case X86::CMOVAE64rm: return X86::CMOVBE64rm;
+ case X86::CMOVAE64rr: return X86::CMOVBE64rr;
+ }
+}
+
+bool X86InstrInfo::
+OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpMask,
+ int CmpValue, const MachineRegisterInfo *MRI) const {
+ MachineRegisterInfo::def_iterator DI = MRI->def_begin(SrcReg);
+ if (llvm::next(DI) != MRI->def_end())
+ // Only support one definition.
+ return false;
+
+ MachineInstr *MI = &*DI;
+ // Get ready to iterate backward from CmpInstr.
+ MachineBasicBlock::iterator I = CmpInstr, E = MI,
+ B = CmpInstr->getParent()->begin();
+
+ // Early exit if CmpInstr is at the beginning of the BB.
+ if (I == B) return false;
+
+ // For CMPrr(r1,r2), we are looking for SUB(r1,r2) or SUB(r2,r1).
+ // For CMPri(r1, CmpValue), we are looking for SUBri(r1, CmpValue).
+ MachineInstr *Sub = NULL;
+ unsigned SrcReg2 = 0;
+ if (CmpInstr->getOpcode() == X86::CMP64rr ||
+ CmpInstr->getOpcode() == X86::CMP32rr ||
+ CmpInstr->getOpcode() == X86::CMP16rr ||
+ CmpInstr->getOpcode() == X86::CMP8rr) {
+ SrcReg2 = CmpInstr->getOperand(1).getReg();
+ }
+
+ // Search backwards for a SUB instruction.
+ // If EFLAGS is updated in the middle, we can not remove the CMP instruction.
+ --I;
+ for (; I != E; --I) {
+ const MachineInstr &Instr = *I;
+
+ // Check whether the current instruction is SUB(r1, r2) or SUB(r2, r1).
+ if (((CmpInstr->getOpcode() == X86::CMP64rr &&
+ Instr.getOpcode() == X86::SUB64rr) ||
+ (CmpInstr->getOpcode() == X86::CMP32rr &&
+ Instr.getOpcode() == X86::SUB32rr)||
+ (CmpInstr->getOpcode() == X86::CMP16rr &&
+ Instr.getOpcode() == X86::SUB16rr)||
+ (CmpInstr->getOpcode() == X86::CMP8rr &&
+ Instr.getOpcode() == X86::SUB8rr)) &&
+ ((Instr.getOperand(1).getReg() == SrcReg &&
+ Instr.getOperand(2).getReg() == SrcReg2) ||
+ (Instr.getOperand(1).getReg() == SrcReg2 &&
+ Instr.getOperand(2).getReg() == SrcReg))) {
+ Sub = &*I;
+ break;
+ }
+
+ // Check whether the current instruction is SUBri(r1, CmpValue).
+ if (((CmpInstr->getOpcode() == X86::CMP64ri32 &&
+ Instr.getOpcode() == X86::SUB64ri32) ||
+ (CmpInstr->getOpcode() == X86::CMP64ri8 &&
+ Instr.getOpcode() == X86::SUB64ri8) ||
+ (CmpInstr->getOpcode() == X86::CMP32ri &&
+ Instr.getOpcode() == X86::SUB32ri) ||
+ (CmpInstr->getOpcode() == X86::CMP32ri8 &&
+ Instr.getOpcode() == X86::SUB32ri8) ||
+ (CmpInstr->getOpcode() == X86::CMP16ri &&
+ Instr.getOpcode() == X86::SUB16ri) ||
+ (CmpInstr->getOpcode() == X86::CMP16ri8 &&
+ Instr.getOpcode() == X86::SUB16ri8) ||
+ (CmpInstr->getOpcode() == X86::CMP8ri &&
+ Instr.getOpcode() == X86::SUB8ri)) &&
+ CmpValue != 0 &&
+ Instr.getOperand(1).getReg() == SrcReg &&
+ Instr.getOperand(2).getImm() == CmpValue) {
+ Sub = &*I;
+ break;
+ }
+
+ for (unsigned IO = 0, EO = Instr.getNumOperands(); IO != EO; ++IO) {
+ const MachineOperand &MO = Instr.getOperand(IO);
+ if (MO.isRegMask() && MO.clobbersPhysReg(X86::EFLAGS))
+ return false;
+ if (!MO.isReg()) continue;
+
+ // This instruction modifies or uses EFLAGS before we find a SUB.
+ // We can't do this transformation.
+ if (MO.getReg() == X86::EFLAGS)
+ return false;
+ }
+
+ if (I == B)
+ // Reaching beginning of the block.
+ return false;
+ }
+
+ // Return false if no candidates exist.
+ if (!Sub)
+ return false;
+ MI = Sub;
+
+ switch (MI->getOpcode()) {
+ default: break;
+ case X86::SUB64rr:
+ case X86::SUB32rr:
+ case X86::SUB16rr:
+ case X86::SUB8rr:
+ case X86::SUB64ri32:
+ case X86::SUB64ri8:
+ case X86::SUB32ri:
+ case X86::SUB32ri8:
+ case X86::SUB16ri:
+ case X86::SUB16ri8:
+ case X86::SUB8ri: {
+ // Scan forward from CmpInstr for the use of EFLAGS.
+ // Handle the condition codes GE, L, G, LE, B, L, BE, LE.
+ SmallVector<std::pair<MachineInstr*, unsigned /*NewOpc*/>, 4> OpsToUpdate;
+ bool isSafe = false;
+ I = CmpInstr;
+ E = CmpInstr->getParent()->end();
+ while (!isSafe && ++I != E) {
+ const MachineInstr &Instr = *I;
+ for (unsigned IO = 0, EO = Instr.getNumOperands();
+ !isSafe && IO != EO; ++IO) {
+ const MachineOperand &MO = Instr.getOperand(IO);
+ if (MO.isRegMask() && MO.clobbersPhysReg(X86::EFLAGS)) {
+ isSafe = true;
+ break;
+ }
+ if (!MO.isReg() || MO.getReg() != X86::EFLAGS)
+ continue;
+ // EFLAGS is redefined by this instruction.
+ if (MO.isDef()) {
+ isSafe = true;
+ break;
+ }
+ // EFLAGS is used by this instruction.
+
+ // If we have SUB(r1, r2) and CMP(r2, r1), the condition code needs
+ // to be changed from r2 > r1 to r1 < r2, from r2 < r1 to r1 > r2, etc.
+ unsigned NewOpc = UpdateBranchCondToOptimizeCmp(Instr.getOpcode());
+ if (!NewOpc) NewOpc = UpdateSETCondToOptimizeCmp(Instr.getOpcode());
+ if (!NewOpc) NewOpc = UpdateCMovCondToOptimizeCmp(Instr.getOpcode());
+ if (!NewOpc) return false;
+
+ // Push the MachineInstr to OpsToUpdate.
+ // If it is safe to remove CmpInstr, the condition code of these
+ // instructions will be modified.
+ if (SrcReg2 != 0 && Sub->getOperand(1).getReg() == SrcReg2 &&
+ Sub->getOperand(2).getReg() == SrcReg)
+ OpsToUpdate.push_back(std::make_pair(&*I, NewOpc));
+ }
+ }
+
+ // We may exit the loop at end of the basic block.
+ // In that case, it is still safe to remove CmpInstr.
+
+ // Make sure Sub instruction defines EFLAGS.
+ assert(MI->getOperand(3).getReg() == X86::EFLAGS &&
+ "Expected EFLAGS is the 4th operand of SUBrr or SUBri.");
+ MI->getOperand(3).setIsDef(true);
+ CmpInstr->eraseFromParent();
+
+ // Modify the condition code of instructions in OpsToUpdate.
+ for (unsigned i = 0; i < OpsToUpdate.size(); i++)
+ OpsToUpdate[i].first->setDesc(get(OpsToUpdate[i].second));
+ NumCmpsRemoved++;
+ return true;
+ }
+ }
+
+ return false;
+}
+
bool X86InstrInfo::
OptimizeSubInstr(MachineInstr *SubInstr, const MachineRegisterInfo *MRI) const {
// If destination is a memory operand, do not perform this optimization.
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