[llvm-commits] CVS: llvm/lib/Target/X86/InstSelectSimple.cpp
Chris Lattner
lattner at cs.uiuc.edu
Mon Dec 16 13:34:01 PST 2002
Changes in directory llvm/lib/Target/X86:
InstSelectSimple.cpp updated: 1.71 -> 1.72
---
Log message:
Add some special cases to make common getelementptr cases easier to read/faster
---
Diffs of the changes:
Index: llvm/lib/Target/X86/InstSelectSimple.cpp
diff -u llvm/lib/Target/X86/InstSelectSimple.cpp:1.71 llvm/lib/Target/X86/InstSelectSimple.cpp:1.72
--- llvm/lib/Target/X86/InstSelectSimple.cpp:1.71 Sun Dec 15 22:23:29 2002
+++ llvm/lib/Target/X86/InstSelectSimple.cpp Mon Dec 16 13:32:50 2002
@@ -124,10 +124,9 @@
void visitSimpleBinary(BinaryOperator &B, unsigned OpcodeClass);
void visitAdd(BinaryOperator &B) { visitSimpleBinary(B, 0); }
void visitSub(BinaryOperator &B) { visitSimpleBinary(B, 1); }
- void doMultiply(unsigned destReg, const Type *resultType,
- unsigned op0Reg, unsigned op1Reg,
- MachineBasicBlock *MBB,
- MachineBasicBlock::iterator &MBBI);
+ void doMultiply(MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI,
+ unsigned destReg, const Type *resultType,
+ unsigned op0Reg, unsigned op1Reg);
void visitMul(BinaryOperator &B);
void visitDiv(BinaryOperator &B) { visitDivRem(B); }
@@ -179,9 +178,9 @@
/// copyConstantToRegister - Output the instructions required to put the
/// specified constant into the specified register.
///
- void copyConstantToRegister(Constant *C, unsigned Reg,
- MachineBasicBlock *MBB,
- MachineBasicBlock::iterator &MBBI);
+ void copyConstantToRegister(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &MBBI,
+ Constant *C, unsigned Reg);
/// makeAnotherReg - This method returns the next register number
/// we haven't yet used.
@@ -213,7 +212,7 @@
// the register here...
//
if (Constant *C = dyn_cast<Constant>(V)) {
- copyConstantToRegister(C, Reg, MBB, IPt);
+ copyConstantToRegister(MBB, IPt, C, Reg);
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
// Move the address of the global into the register
BMI(MBB, IPt, X86::MOVir32, 1, Reg).addReg(GV);
@@ -287,9 +286,9 @@
/// copyConstantToRegister - Output the instructions required to put the
/// specified constant into the specified register.
///
-void ISel::copyConstantToRegister(Constant *C, unsigned R,
- MachineBasicBlock *MBB,
- MachineBasicBlock::iterator &IP) {
+void ISel::copyConstantToRegister(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &IP,
+ Constant *C, unsigned R) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
emitGEPOperation(MBB, IP, CE->getOperand(0),
@@ -669,11 +668,9 @@
/// doMultiply - Emit appropriate instructions to multiply together
/// the registers op0Reg and op1Reg, and put the result in destReg.
/// The type of the result should be given as resultType.
-void
-ISel::doMultiply(unsigned destReg, const Type *resultType,
- unsigned op0Reg, unsigned op1Reg,
- MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI)
-{
+void ISel::doMultiply(MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI,
+ unsigned destReg, const Type *resultType,
+ unsigned op0Reg, unsigned op1Reg) {
unsigned Class = getClass (resultType);
// FIXME:
@@ -704,7 +701,7 @@
unsigned Op0Reg = getReg(I.getOperand(0));
unsigned Op1Reg = getReg(I.getOperand(1));
MachineBasicBlock::iterator MBBI = BB->end();
- doMultiply(DestReg, I.getType(), Op0Reg, Op1Reg, BB, MBBI);
+ doMultiply(BB, MBBI, DestReg, I.getType(), Op0Reg, Op1Reg);
}
@@ -934,6 +931,19 @@
visitInstruction (CI);
}
+// ExactLog2 - This function solves for (Val == 1 << (N-1)) and returns N. It
+// returns zero when the input is not exactly a power of two.
+static unsigned ExactLog2(unsigned Val) {
+ if (Val == 0) return 0;
+ unsigned Count = 0;
+ while (Val != 1) {
+ if (Val & 1) return 0;
+ Val >>= 1;
+ ++Count;
+ }
+ return Count+1;
+}
+
/// visitGetElementPtrInst - I don't know, most programs don't have
/// getelementptr instructions, right? That means we can put off
/// implementing this, right? Right. This method emits machine
@@ -983,34 +993,56 @@
// The next type is the member of the structure selected by the
// index.
Ty = StTy->getElementTypes ()[idxValue];
- } else if (const SequentialType *SqTy = cast <SequentialType> (Ty)) {
+ } else if (const SequentialType *SqTy = cast <SequentialType>(Ty)) {
// It's an array or pointer access: [ArraySize x ElementType].
- const Type *typeOfSequentialTypeIndex = SqTy->getIndexType ();
+
// idx is the index into the array. Unlike with structure
// indices, we may not know its actual value at code-generation
// time.
- assert (idx->getType () == typeOfSequentialTypeIndex
- && "Funny-looking array index in GEP");
- // We want to add basePtrReg to (idxReg * sizeof
- // ElementType). First, we must find the size of the pointed-to
- // type. (Not coincidentally, the next type is the type of the
- // elements in the array.)
- Ty = SqTy->getElementType ();
- unsigned elementSize = TD.getTypeSize (Ty);
- unsigned elementSizeReg = makeAnotherReg(typeOfSequentialTypeIndex);
- copyConstantToRegister(ConstantSInt::get(typeOfSequentialTypeIndex,
- elementSize), elementSizeReg,
- MBB, IP);
-
- unsigned idxReg = getReg(idx, MBB, IP);
- // Emit a MUL to multiply the register holding the index by
- // elementSize, putting the result in memberOffsetReg.
- unsigned memberOffsetReg = makeAnotherReg(Type::UIntTy);
- doMultiply (memberOffsetReg, typeOfSequentialTypeIndex,
- elementSizeReg, idxReg, MBB, IP);
- // Emit an ADD to add memberOffsetReg to the basePtr.
- BMI(MBB, IP, X86::ADDrr32, 2,
- nextBasePtrReg).addReg (basePtrReg).addReg (memberOffsetReg);
+ assert(idx->getType() == Type::LongTy && "Bad GEP array index!");
+
+ // We want to add basePtrReg to (idxReg * sizeof ElementType). First, we
+ // must find the size of the pointed-to type (Not coincidentally, the next
+ // type is the type of the elements in the array).
+ Ty = SqTy->getElementType();
+ unsigned elementSize = TD.getTypeSize(Ty);
+
+ // If idxReg is a constant, we don't need to perform the multiply!
+ if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(idx)) {
+ if (CSI->isNullValue()) {
+ BMI(MBB, IP, X86::MOVrr32, 1, nextBasePtrReg).addReg(basePtrReg);
+ } else {
+ unsigned Offset = elementSize*CSI->getValue();
+
+ BMI(MBB, IP, X86::ADDri32, 2,
+ nextBasePtrReg).addReg(basePtrReg).addZImm(Offset);
+ }
+ } else if (elementSize == 1) {
+ // If the element size is 1, we don't have to multiply, just add
+ unsigned idxReg = getReg(idx, MBB, IP);
+ BMI(MBB, IP, X86::ADDrr32, 2,
+ nextBasePtrReg).addReg(basePtrReg).addReg(idxReg);
+ } else {
+ unsigned idxReg = getReg(idx, MBB, IP);
+ unsigned OffsetReg = makeAnotherReg(Type::UIntTy);
+ if (unsigned Shift = ExactLog2(elementSize)) {
+ // If the element size is exactly a power of 2, use a shift to get it.
+
+ BMI(MBB, IP, X86::SHLir32, 2,
+ OffsetReg).addReg(idxReg).addZImm(Shift-1);
+ } else {
+ // Most general case, emit a multiply...
+ unsigned elementSizeReg = makeAnotherReg(Type::LongTy);
+ BMI(MBB, IP, X86::MOVir32, 1, elementSizeReg).addZImm(elementSize);
+
+ // Emit a MUL to multiply the register holding the index by
+ // elementSize, putting the result in OffsetReg.
+ doMultiply(MBB, IP, OffsetReg, Type::LongTy, idxReg, elementSizeReg);
+ }
+ // Emit an ADD to add OffsetReg to the basePtr.
+ BMI(MBB, IP, X86::ADDrr32, 2,
+ nextBasePtrReg).addReg (basePtrReg).addReg (OffsetReg);
+ }
}
// Now that we are here, further indices refer to subtypes of this
// one, so we don't need to worry about basePtrReg itself, anymore.
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