diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp index 9744af3c605..b1dd58331b6 100644 --- a/lib/Transforms/Utils/Local.cpp +++ b/lib/Transforms/Utils/Local.cpp @@ -12,11 +12,13 @@ // //===----------------------------------------------------------------------===// -#include "llvm/Support/MathExtras.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" #include "llvm/Instructions.h" #include "llvm/Intrinsics.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/MathExtras.h" #include #include using namespace llvm; @@ -366,6 +368,48 @@ Constant *llvm::ConstantFoldCall(Function *F, } +/// 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(*I)) { + ConstantUInt *CU = cast(I.getOperand()); + assert(CU->getValue() < STy->getNumElements() && + "Struct index out of range!"); + unsigned El = (unsigned)CU->getValue(); + if (ConstantStruct *CS = dyn_cast(C)) { + C = CS->getOperand(El); + } else if (isa(C)) { + C = Constant::getNullValue(STy->getElementType(El)); + } else if (isa(C)) { + C = UndefValue::get(STy->getElementType(El)); + } else { + return 0; + } + } else if (ConstantInt *CI = dyn_cast(I.getOperand())) { + const ArrayType *ATy = cast(*I); + if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0; + if (ConstantArray *CA = dyn_cast(C)) + C = CA->getOperand((unsigned)CI->getRawValue()); + else if (isa(C)) + C = Constant::getNullValue(ATy->getElementType()); + else if (isa(C)) + C = UndefValue::get(ATy->getElementType()); + else + return 0; + } else { + return 0; + } + return C; +} //===----------------------------------------------------------------------===//