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Do trivial local CSE for constants and other non-Instruction values

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in FastISel.

llvm-svn: 55748
This commit is contained in:
Dan Gohman 2008-09-03 23:32:19 +00:00
parent f86538dd3c
commit 18f659d804
2 changed files with 16 additions and 12 deletions
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1
include/llvm/CodeGen/FastISel.h
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@ -36,6 +36,7 @@ class TargetRegisterClass;
class FastISel {
protected:
MachineBasicBlock *MBB;
DenseMap<const Value *, unsigned> LocalValueMap;
DenseMap<const Value *, unsigned> &ValueMap;
DenseMap<const BasicBlock *, MachineBasicBlock *> &MBBMap;
MachineFunction &MF;

27
lib/CodeGen/SelectionDAG/FastISel.cpp
View File

@ -21,13 +21,16 @@
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
// Don't cache constant materializations. To do so would require
// tracking what uses they dominate. Non-constants, however, already
// have the SSA def-doms-use requirement enforced, so we can cache their
// computations.
unsigned FastISel::getRegForValue(Value *V) {
// Look up the value to see if we already have a register for it. We
// cache values defined by Instructions across blocks, and other values
// only locally. This is because Instructions already have the SSA
// def-dominatess-use requirement enforced.
if (ValueMap.count(V))
return ValueMap[V];
unsigned Reg = LocalValueMap[V];
if (Reg != 0)
return Reg;
MVT::SimpleValueType VT = TLI.getValueType(V->getType()).getSimpleVT();
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
@ -35,11 +38,11 @@ unsigned FastISel::getRegForValue(Value *V) {
return 0;
// Don't cache constant materializations. To do so would require
// tracking what uses they dominate.
return FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
Reg = FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
} else if (isa<ConstantPointerNull>(V)) {
return FastEmit_i(VT, VT, ISD::Constant, 0);
Reg = FastEmit_i(VT, VT, ISD::Constant, 0);
} else if (ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
unsigned Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
if (!Reg) {
const APFloat &Flt = CF->getValueAPF();
@ -60,15 +63,15 @@ unsigned FastISel::getRegForValue(Value *V) {
if (Reg == 0)
return 0;
}
return Reg;
} else if (isa<UndefValue>(V)) {
unsigned Reg = createResultReg(TLI.getRegClassFor(VT));
Reg = createResultReg(TLI.getRegClassFor(VT));
BuildMI(MBB, TII.get(TargetInstrInfo::IMPLICIT_DEF), Reg);
return Reg;
} else {
return 0;
}
return 0;
LocalValueMap[V] = Reg;
return Reg;
}
/// UpdateValueMap - Update the value map to include the new mapping for this