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Teach lib/VMCore/ConstantFold.cpp how to set the inbounds keyword and
how to fold notionally-out-of-bounds array getelementptr indices instead of just doing these in lib/Analysis/ConstantFolding.cpp, because it can be done in a fairly general way without TargetData, and because not all constants are visited by lib/Analysis/ConstantFolding.cpp. This enables more constant folding. Also, set the "inbounds" flag when the getelementptr indices are one-past-the-end. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81483 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
parent
e6992f728a
commit
3bfbc4587a
@ -207,12 +207,8 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
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if (Offset != 0)
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return 0;
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// If the base is the start of a GlobalVariable and all the array indices
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// remain in their static bounds, the GEP is inbounds. We can check that
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// all indices are in bounds by just checking the first index only
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// because we've just normalized all the indices.
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Constant *C = isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue() ?
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ConstantExpr::getInBoundsGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()) :
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// Create a GEP.
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Constant *C =
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ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
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assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
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"Computed GetElementPtr has unexpected type!");
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@ -12,9 +12,8 @@
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// ConstantExpr::get* methods to automatically fold constants when possible.
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//
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// The current constant folding implementation is implemented in two pieces: the
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// template-based folder for simple primitive constants like ConstantInt, and
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// the special case hackery that we use to symbolically evaluate expressions
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// that use ConstantExprs.
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// pieces that don't need TargetData, and the pieces that do. This is to avoid
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// a dependence in VMCore on Target.
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//
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//===----------------------------------------------------------------------===//
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@ -24,6 +23,7 @@
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/GlobalAlias.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Support/Compiler.h"
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@ -1673,8 +1673,28 @@ Constant *llvm::ConstantFoldCompareInstruction(LLVMContext &Context,
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return 0;
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}
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/// isInBoundsIndices - Test whether the given sequence of *normalized* indices
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/// is "inbounds".
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static bool isInBoundsIndices(Constant *const *Idxs, size_t NumIdx) {
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// No indices means nothing that could be out of bounds.
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if (NumIdx == 0) return true;
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// If the first index is zero, it's in bounds.
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if (Idxs[0]->isNullValue()) return true;
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// If the first index is one and all the rest are zero, it's in bounds,
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// by the one-past-the-end rule.
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if (!cast<ConstantInt>(Idxs[0])->isOne())
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return false;
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for (unsigned i = 1, e = NumIdx; i != e; ++i)
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if (!Idxs[i]->isNullValue())
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return false;
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return true;
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}
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Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
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const Constant *C,
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bool inBounds,
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Constant* const *Idxs,
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unsigned NumIdx) {
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if (NumIdx == 0 ||
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@ -1746,9 +1766,13 @@ Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
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NewIndices.push_back(Combined);
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NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
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return ConstantExpr::getGetElementPtr(CE->getOperand(0),
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&NewIndices[0],
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NewIndices.size());
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return (inBounds && cast<GEPOperator>(CE)->isInBounds()) ?
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ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0),
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&NewIndices[0],
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NewIndices.size()) :
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ConstantExpr::getGetElementPtr(CE->getOperand(0),
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&NewIndices[0],
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NewIndices.size());
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}
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}
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@ -1764,7 +1788,10 @@ Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
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if (const ArrayType *CAT =
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dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
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if (CAT->getElementType() == SAT->getElementType())
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return ConstantExpr::getGetElementPtr(
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return inBounds ?
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ConstantExpr::getInBoundsGetElementPtr(
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(Constant*)CE->getOperand(0), Idxs, NumIdx) :
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ConstantExpr::getGetElementPtr(
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(Constant*)CE->getOperand(0), Idxs, NumIdx);
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}
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@ -1789,5 +1816,71 @@ Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
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return ConstantExpr::getIntToPtr(Base, CE->getType());
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}
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}
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// Check to see if any array indices are not within the corresponding
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// notional array bounds. If so, try to determine if they can be factored
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// out into preceding dimensions.
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bool Unknown = false;
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SmallVector<Constant *, 8> NewIdxs;
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const Type *Ty = C->getType();
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const Type *Prev = 0;
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for (unsigned i = 0; i != NumIdx;
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Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
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if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
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if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
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if (ATy->getNumElements() <= INT64_MAX &&
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ATy->getNumElements() != 0 &&
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CI->getSExtValue() >= (int64_t)ATy->getNumElements()) {
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if (isa<SequentialType>(Prev)) {
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// It's out of range, but we can factor it into the prior
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// dimension.
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NewIdxs.resize(NumIdx);
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ConstantInt *Factor = ConstantInt::get(CI->getType(),
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ATy->getNumElements());
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NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
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Constant *PrevIdx = Idxs[i-1];
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Constant *Div = ConstantExpr::getSDiv(CI, Factor);
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// Before adding, extend both operands to i64 to avoid
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// overflow trouble.
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if (PrevIdx->getType() != Type::getInt64Ty(Context))
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PrevIdx = ConstantExpr::getSExt(PrevIdx,
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Type::getInt64Ty(Context));
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if (Div->getType() != Type::getInt64Ty(Context))
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Div = ConstantExpr::getSExt(Div,
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Type::getInt64Ty(Context));
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NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
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} else {
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// It's out of range, but the prior dimension is a struct
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// so we can't do anything about it.
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Unknown = true;
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}
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}
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} else {
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// We don't know if it's in range or not.
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Unknown = true;
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}
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}
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// If we did any factoring, start over with the adjusted indices.
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if (!NewIdxs.empty()) {
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for (unsigned i = 0; i != NumIdx; ++i)
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if (!NewIdxs[i]) NewIdxs[i] = Idxs[i];
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return inBounds ?
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ConstantExpr::getGetElementPtr(const_cast<Constant*>(C),
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NewIdxs.data(), NewIdxs.size()) :
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ConstantExpr::getInBoundsGetElementPtr(const_cast<Constant*>(C),
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NewIdxs.data(), NewIdxs.size());
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}
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// If all indices are known integers and normalized, we can do a simple
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// check for the "inbounds" property.
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if (!Unknown && !inBounds &&
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isa<GlobalVariable>(C) && isInBoundsIndices(Idxs, NumIdx))
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return ConstantExpr::getInBoundsGetElementPtr(const_cast<Constant*>(C),
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Idxs, NumIdx);
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return 0;
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}
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@ -64,6 +64,7 @@ namespace llvm {
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const Constant *C1,
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const Constant *C2);
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Constant *ConstantFoldGetElementPtr(LLVMContext &Context, const Constant *C,
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bool inBounds,
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Constant* const *Idxs, unsigned NumIdx);
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} // End llvm namespace
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@ -1489,7 +1489,8 @@ Constant *ConstantExpr::getGetElementPtrTy(const Type *ReqTy, Constant *C,
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"GEP indices invalid!");
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if (Constant *FC = ConstantFoldGetElementPtr(
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ReqTy->getContext(), C, (Constant**)Idxs, NumIdx))
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ReqTy->getContext(), C, /*inBounds=*/false,
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(Constant**)Idxs, NumIdx))
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return FC; // Fold a few common cases...
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assert(isa<PointerType>(C->getType()) &&
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@ -1518,7 +1519,8 @@ Constant *ConstantExpr::getInBoundsGetElementPtrTy(const Type *ReqTy,
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"GEP indices invalid!");
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if (Constant *FC = ConstantFoldGetElementPtr(
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ReqTy->getContext(), C, (Constant**)Idxs, NumIdx))
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ReqTy->getContext(), C, /*inBounds=*/true,
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(Constant**)Idxs, NumIdx))
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return FC; // Fold a few common cases...
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assert(isa<PointerType>(C->getType()) &&
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@ -1,11 +1,21 @@
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; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis
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; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
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; Verify that over-indexed getelementptrs are folded.
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@A = external global [2 x [3 x [5 x [7 x i32]]]]
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@B = global i32* getelementptr ([2 x [3 x [5 x [7 x i32]]]]* @A, i64 0, i64 0, i64 2, i64 1, i64 7523)
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; CHECK: @B = global i32* getelementptr ([2 x [3 x [5 x [7 x i32]]]]* @A, i64 36, i64 0, i64 1, i64 0, i64 5) ; <i32**> [#uses=0]
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@C = global i32* getelementptr ([2 x [3 x [5 x [7 x i32]]]]* @A, i64 3, i64 2, i64 0, i64 0, i64 7523)
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; CHECK: @C = global i32* getelementptr ([2 x [3 x [5 x [7 x i32]]]]* @A, i64 39, i64 1, i64 1, i64 4, i64 5) ; <i32**> [#uses=0]
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;; Verify that i16 indices work.
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@x = external global {i32, i32}
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@y = global i32* getelementptr ({i32, i32}* @x, i16 42, i32 0)
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; CHECK: @y = global i32* getelementptr (%0* @x, i16 42, i32 0)
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; see if i92 indices work too.
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define i32 *@test({i32, i32}* %t, i92 %n) {
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; CHECK: @test
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; CHECK: %B = getelementptr %0* %t, i92 %n, i32 0
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%B = getelementptr {i32, i32}* %t, i92 %n, i32 0
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ret i32* %B
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}
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@ -44,7 +44,11 @@ define void @frob() {
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store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 16), align 8
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; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 0, i64 2, i32 1, i64 2), align 8
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store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 17), align 8
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; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 1, i64 0, i32 0, i64 0), align 8
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; CHECK: store i32 1, i32* getelementptr inbounds ([3 x %struct.X]* @Y, i64 1, i64 0, i32 0, i64 0), align 8
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store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 18), align 8
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; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 2, i64 0, i32 0, i64 0), align 8
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store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 36), align 8
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; CHECK: store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 1, i64 0, i32 0, i64 1), align 8
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store i32 1, i32* getelementptr ([3 x %struct.X]* @Y, i64 0, i64 0, i32 0, i64 19), align 8
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ret void
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}
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@ -222,7 +222,7 @@ define i1 @test22() {
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getelementptr (i32* @B, i64 2)
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ret i1 %C
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; CHECK: @test22
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; CHECK: icmp ult (i32* getelementptr (i32* @A, i64 1), i32* getelementptr (i32* @B, i64 2))
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; CHECK: icmp ult (i32* getelementptr inbounds (i32* @A, i64 1), i32* getelementptr (i32* @B, i64 2))
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}
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@ -463,7 +463,7 @@ define i8* @test36() nounwind {
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@A37 = external constant [1 x i8]
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define i1 @test37() nounwind {
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; CHECK: @test37
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; CHECK: ret i1 icmp eq (i8* getelementptr ([1 x i8]* @A37, i64 0, i64 1), i8* getelementptr ([1 x i8]* @A37, i64 1, i64 0))
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; CHECK: ret i1 true
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%t = icmp eq i8* getelementptr ([1 x i8]* @A37, i64 0, i64 1),
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getelementptr ([1 x i8]* @A37, i64 1, i64 0)
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ret i1 %t
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