Do trivial local CSE for constants and other non-Instruction values
in FastISel.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55748 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index c057be5..d118eef 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -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 @@
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 @@
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