[llvm-commits] CVS: llvm/lib/Analysis/ConstantFolding.cpp
Chris Lattner
sabre at nondot.org
Tue Jan 30 15:46:01 PST 2007
Changes in directory llvm/lib/Analysis:
ConstantFolding.cpp updated: 1.11 -> 1.12
---
Log message:
move a bunch of constant folding code f rom Transforms/Utils/Local.cpp into
libanalysis/ConstantFolding.cpp.
---
Diffs of the changes: (+155 -2)
ConstantFolding.cpp | 157 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 155 insertions(+), 2 deletions(-)
Index: llvm/lib/Analysis/ConstantFolding.cpp
diff -u llvm/lib/Analysis/ConstantFolding.cpp:1.11 llvm/lib/Analysis/ConstantFolding.cpp:1.12
--- llvm/lib/Analysis/ConstantFolding.cpp:1.11 Tue Jan 30 17:15:43 2007
+++ llvm/lib/Analysis/ConstantFolding.cpp Tue Jan 30 17:45:45 2007
@@ -15,19 +15,172 @@
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include <cerrno>
#include <cmath>
using namespace llvm;
+/// ConstantFoldInstruction - Attempt to constant fold the specified
+/// instruction. If successful, the constant result is returned, if not, null
+/// is returned. Note that this function can only fail when attempting to fold
+/// instructions like loads and stores, which have no constant expression form.
+///
+Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
+ if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ if (PN->getNumIncomingValues() == 0)
+ return Constant::getNullValue(PN->getType());
+
+ Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
+ if (Result == 0) return 0;
+
+ // Handle PHI nodes specially here...
+ for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
+ return 0; // Not all the same incoming constants...
+
+ // If we reach here, all incoming values are the same constant.
+ return Result;
+ }
+
+ // Scan the operand list, checking to see if they are all constants, if so,
+ // hand off to ConstantFoldInstOperands.
+ SmallVector<Constant*, 8> Ops;
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (Constant *Op = dyn_cast<Constant>(I->getOperand(i)))
+ Ops.push_back(Op);
+ else
+ return 0; // All operands not constant!
+
+ return ConstantFoldInstOperands(I, &Ops[0], Ops.size());
+}
+
+/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
+/// specified opcode and operands. If successful, the constant result is
+/// returned, if not, null is returned. Note that this function can fail when
+/// attempting to fold instructions like loads and stores, which have no
+/// constant expression form.
+///
+Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
+ Constant** Ops, unsigned NumOps,
+ const TargetData *TD) {
+ unsigned Opc = I->getOpcode();
+ const Type *DestTy = I->getType();
+
+ // Handle easy binops first
+ if (isa<BinaryOperator>(I))
+ return ConstantExpr::get(Opc, Ops[0], Ops[1]);
+
+ switch (Opc) {
+ default: return 0;
+ case Instruction::Call:
+ if (Function *F = dyn_cast<Function>(Ops[0]))
+ if (canConstantFoldCallTo(F))
+ return ConstantFoldCall(F, Ops+1, NumOps);
+ return 0;
+ case Instruction::ICmp:
+ case Instruction::FCmp:
+ return ConstantExpr::getCompare(cast<CmpInst>(I)->getPredicate(), Ops[0],
+ Ops[1]);
+ case Instruction::Shl:
+ case Instruction::LShr:
+ case Instruction::AShr:
+ return ConstantExpr::get(Opc, Ops[0], Ops[1]);
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ case Instruction::FPTrunc:
+ case Instruction::FPExt:
+ case Instruction::UIToFP:
+ case Instruction::SIToFP:
+ case Instruction::FPToUI:
+ case Instruction::FPToSI:
+ case Instruction::PtrToInt:
+ case Instruction::IntToPtr:
+ case Instruction::BitCast:
+ return ConstantExpr::getCast(Opc, Ops[0], DestTy);
+ case Instruction::Select:
+ return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
+ case Instruction::ExtractElement:
+ return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
+ case Instruction::InsertElement:
+ return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
+ case Instruction::ShuffleVector:
+ return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
+ case Instruction::GetElementPtr:
+ return ConstantExpr::getGetElementPtr(Ops[0],
+ std::vector<Constant*>(Ops+1,
+ Ops+NumOps));
+ }
+}
+
+/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
+/// getelementptr constantexpr, return the constant value being addressed by the
+/// constant expression, or null if something is funny and we can't decide.
+Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
+ ConstantExpr *CE) {
+ if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
+ return 0; // Do not allow stepping over the value!
+
+ // Loop over all of the operands, tracking down which value we are
+ // addressing...
+ gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
+ for (++I; I != E; ++I)
+ if (const StructType *STy = dyn_cast<StructType>(*I)) {
+ ConstantInt *CU = cast<ConstantInt>(I.getOperand());
+ assert(CU->getZExtValue() < STy->getNumElements() &&
+ "Struct index out of range!");
+ unsigned El = (unsigned)CU->getZExtValue();
+ if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
+ C = CS->getOperand(El);
+ } else if (isa<ConstantAggregateZero>(C)) {
+ C = Constant::getNullValue(STy->getElementType(El));
+ } else if (isa<UndefValue>(C)) {
+ C = UndefValue::get(STy->getElementType(El));
+ } else {
+ return 0;
+ }
+ } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
+ if (CI->getZExtValue() >= ATy->getNumElements())
+ return 0;
+ if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
+ C = CA->getOperand(CI->getZExtValue());
+ else if (isa<ConstantAggregateZero>(C))
+ C = Constant::getNullValue(ATy->getElementType());
+ else if (isa<UndefValue>(C))
+ C = UndefValue::get(ATy->getElementType());
+ else
+ return 0;
+ } else if (const PackedType *PTy = dyn_cast<PackedType>(*I)) {
+ if (CI->getZExtValue() >= PTy->getNumElements())
+ return 0;
+ if (ConstantPacked *CP = dyn_cast<ConstantPacked>(C))
+ C = CP->getOperand(CI->getZExtValue());
+ else if (isa<ConstantAggregateZero>(C))
+ C = Constant::getNullValue(PTy->getElementType());
+ else if (isa<UndefValue>(C))
+ C = UndefValue::get(PTy->getElementType());
+ else
+ return 0;
+ } else {
+ return 0;
+ }
+ } else {
+ return 0;
+ }
+ return C;
+}
+
+
//===----------------------------------------------------------------------===//
-// Constant Folding ...
+// Constant Folding for Calls
//
-
/// canConstantFoldCallTo - Return true if its even possible to fold a call to
/// the specified function.
bool
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