[llvm-commits] CVS: llvm/lib/VMCore/ConstantHandling.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu Apr 17 14:25:01 PDT 2003
Changes in directory llvm/lib/VMCore:
ConstantHandling.cpp updated: 1.24 -> 1.25
---
Log message:
Allow constant folding of GEP instructions, even if we don't do a whole lot yet.
Fold ConstExpr casts better
castToPointer shouldn't be forced to return a constantpointer
---
Diffs of the changes:
Index: llvm/lib/VMCore/ConstantHandling.cpp
diff -u llvm/lib/VMCore/ConstantHandling.cpp:1.24 llvm/lib/VMCore/ConstantHandling.cpp:1.25
--- llvm/lib/VMCore/ConstantHandling.cpp:1.24 Tue Sep 3 15:09:49 2002
+++ llvm/lib/VMCore/ConstantHandling.cpp Thu Apr 17 14:24:18 2003
@@ -6,6 +6,7 @@
#include "llvm/ConstantHandling.h"
#include "llvm/iPHINode.h"
+#include "llvm/DerivedTypes.h"
#include <cmath>
AnnotationID ConstRules::AID(AnnotationManager::getID("opt::ConstRules",
@@ -64,12 +65,48 @@
case Instruction::SetGT: return *Op0 > *Op1;
case Instruction::Shl: return *Op0 << *Op1;
case Instruction::Shr: return *Op0 >> *Op1;
+ case Instruction::GetElementPtr: {
+ std::vector<Constant*> IdxList;
+ IdxList.reserve(I->getNumOperands()-1);
+ if (Op1) IdxList.push_back(Op1);
+ for (unsigned i = 2, e = I->getNumOperands(); i != e; ++i)
+ if (Constant *C = dyn_cast<Constant>(I->getOperand(i)))
+ IdxList.push_back(C);
+ else
+ return 0; // Non-constant operand
+ return ConstantFoldGetElementPtr(Op0, IdxList);
+ }
default:
return 0;
}
}
+static unsigned getSize(const Type *Ty) {
+ unsigned S = Ty->getPrimitiveSize();
+ return S ? S : 8; // Treat pointers at 8 bytes
+}
+
Constant *ConstantFoldCastInstruction(const Constant *V, const Type *DestTy) {
+ if (V->getType() == DestTy) return (Constant*)V;
+
+ if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
+ if (CE->getOpcode() == Instruction::Cast) {
+ Constant *Op = (Constant*)cast<Constant>(CE->getOperand(0));
+ // Try to not produce a cast of a cast, which is almost always redundant.
+ if (!Op->getType()->isFloatingPoint() &&
+ !CE->getType()->isFloatingPoint() &&
+ !DestTy->getType()->isFloatingPoint()) {
+ unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType());
+ unsigned S3 = getSize(DestTy);
+ if (Op->getType() == DestTy && S3 >= S2)
+ return Op;
+ if (S1 >= S2 && S2 >= S3)
+ return ConstantExpr::getCast(Op, DestTy);
+ if (S1 <= S2 && S2 >= S3 && S1 <= S3)
+ return ConstantExpr::getCast(Op, DestTy);
+ }
+ }
+
return ConstRules::get(*V)->castTo(V, DestTy);
}
@@ -104,6 +141,18 @@
}
}
+Constant *ConstantFoldGetElementPtr(const Constant *C,
+ const std::vector<Constant*> &IdxList) {
+ if (IdxList.size() == 0 ||
+ (IdxList.size() == 1 && IdxList[0]->isNullValue()))
+ return const_cast<Constant*>(C);
+
+ // If C is null and all idx's are null, return null of the right type.
+
+ // FIXME: Implement folding of GEP constant exprs the same as instcombine does
+ return 0;
+}
+
//===----------------------------------------------------------------------===//
// TemplateRules Class
@@ -194,8 +243,8 @@
virtual ConstantFP *castToDouble(const Constant *V) const {
return SubClassName::CastToDouble((const ArgType*)V);
}
- virtual ConstantPointer *castToPointer(const Constant *V,
- const PointerType *Ty) const {
+ virtual Constant *castToPointer(const Constant *V,
+ const PointerType *Ty) const {
return SubClassName::CastToPointer((const ArgType*)V, Ty);
}
@@ -229,8 +278,8 @@
static ConstantUInt *CastToULong (const Constant *V) { return 0; }
static ConstantFP *CastToFloat (const Constant *V) { return 0; }
static ConstantFP *CastToDouble(const Constant *V) { return 0; }
- static ConstantPointer *CastToPointer(const Constant *,
- const PointerType *) {return 0;}
+ static Constant *CastToPointer(const Constant *,
+ const PointerType *) {return 0;}
};
@@ -324,8 +373,8 @@
return 0; // Can't const prop other types of pointers
}
- static ConstantPointer *CastToPointer(const ConstantPointer *V,
- const PointerType *PTy) {
+ static Constant *CastToPointer(const ConstantPointer *V,
+ const PointerType *PTy) {
if (V->getType() == PTy)
return const_cast<ConstantPointer*>(V); // Allow cast %PTy %ptr to %PTy
if (V->isNullValue())
@@ -372,8 +421,8 @@
return ConstantBool::get(R);
}
- static ConstantPointer *CastToPointer(const ConstantClass *V,
- const PointerType *PTy) {
+ static Constant *CastToPointer(const ConstantClass *V,
+ const PointerType *PTy) {
if (V->isNullValue()) // Is it a FP or Integral null value?
return ConstantPointerNull::get(PTy);
return 0; // Can't const prop other types of pointers
@@ -462,7 +511,6 @@
return ConstantClass::get(*Ty, Result);
}
};
-
//===----------------------------------------------------------------------===//
// DirectRules Subclasses
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