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Fix PR1850 by removing an unsafe transformation from VMCore/ConstantFold.cpp.

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Reimplement the xform in Analysis/ConstantFolding.cpp where we can use
targetdata to validate that it is safe.  While I'm in there, fix some const
correctness issues and generalize the interface to the "operand folder".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44817 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-12-10 22:53:04 +00:00
parent 9324665a78
commit f286f6fd93
7 changed files with 134 additions and 43 deletions
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20
include/llvm/Analysis/ConstantFolding.h
View File

@ -21,6 +21,7 @@ namespace llvm {
class Instruction;
class TargetData;
class Function;
class Type;
/// ConstantFoldInstruction - Attempt to constant fold the specified
/// instruction. If successful, the constant result is returned, if not, null
@ -35,12 +36,17 @@ Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0);
/// fold instructions like loads and stores, which have no constant expression
/// form.
///
Constant *ConstantFoldInstOperands(
const Instruction *I, ///< The model instruction
Constant** Ops, ///< The array of constant operands to use.
unsigned NumOps, ///< The number of operands provided.
const TargetData *TD = 0 ///< Optional target information.
);
Constant *ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
Constant*const * Ops, unsigned NumOps,
const TargetData *TD = 0);
/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
/// instruction (icmp/fcmp) with the specified operands. If it fails, it
/// returns a constant expression of the specified operands.
///
Constant *ConstantFoldCompareInstOperands(unsigned Predicate,
Constant*const * Ops, unsigned NumOps,
const TargetData *TD = 0);
/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
@ -55,7 +61,7 @@ bool canConstantFoldCallTo(Function *F);
/// ConstantFoldCall - Attempt to constant fold a call to the specified function
/// with the specified arguments, returning null if unsuccessful.
Constant *
ConstantFoldCall(Function *F, Constant** Operands, unsigned NumOperands);
ConstantFoldCall(Function *F, Constant* const* Operands, unsigned NumOperands);
}
#endif

100
lib/Analysis/ConstantFolding.cpp
View File

@ -55,7 +55,8 @@ static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
if (CE->getOpcode() == Instruction::GetElementPtr) {
// Cannot compute this if the element type of the pointer is missing size
// info.
if (!cast<PointerType>(CE->getOperand(0)->getType())->getElementType()->isSized())
if (!cast<PointerType>(CE->getOperand(0)->getType())
->getElementType()->isSized())
return false;
// If the base isn't a global+constant, we aren't either.
@ -117,7 +118,7 @@ static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
/// constant expression, do so.
static Constant *SymbolicallyEvaluateGEP(Constant** Ops, unsigned NumOps,
static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
const Type *ResultTy,
const TargetData *TD) {
Constant *Ptr = Ops[0];
@ -181,7 +182,12 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
else
return 0; // All operands not constant!
return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD);
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(),
&Ops[0], Ops.size(), TD);
else
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Ops[0], Ops.size(), TD);
}
/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
@ -190,23 +196,19 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
/// attempting to fold instructions like loads and stores, which have no
/// constant expression form.
///
Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
Constant** Ops, unsigned NumOps,
Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
Constant* const* Ops, unsigned NumOps,
const TargetData *TD) {
unsigned Opc = I->getOpcode();
const Type *DestTy = I->getType();
// Handle easy binops first.
if (isa<BinaryOperator>(I)) {
if (Instruction::isBinaryOp(Opcode)) {
if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
if (Constant *C = SymbolicallyEvaluateBinop(I->getOpcode(), Ops[0],
Ops[1], TD))
if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
return C;
return ConstantExpr::get(Opc, Ops[0], Ops[1]);
return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
}
switch (Opc) {
switch (Opcode) {
default: return 0;
case Instruction::Call:
if (Function *F = dyn_cast<Function>(Ops[0]))
@ -215,8 +217,7 @@ Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
return 0;
case Instruction::ICmp:
case Instruction::FCmp:
return ConstantExpr::getCompare(cast<CmpInst>(I)->getPredicate(), Ops[0],
Ops[1]);
assert(0 &&"This function is invalid for compares: no predicate specified");
case Instruction::PtrToInt:
// If the input is a inttoptr, eliminate the pair. This requires knowing
// the width of a pointer, so it can't be done in ConstantExpr::getCast.
@ -229,7 +230,7 @@ Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
TD->getPointerSizeInBits()));
Input = ConstantExpr::getAnd(Input, Mask);
// Do a zext or trunc to get to the dest size.
return ConstantExpr::getIntegerCast(Input, I->getType(), false);
return ConstantExpr::getIntegerCast(Input, DestTy, false);
}
}
// FALL THROUGH.
@ -244,7 +245,7 @@ Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::BitCast:
return ConstantExpr::getCast(Opc, Ops[0], DestTy);
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::Select:
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
case Instruction::ExtractElement:
@ -254,13 +255,73 @@ Constant *llvm::ConstantFoldInstOperands(const Instruction* I,
case Instruction::ShuffleVector:
return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
case Instruction::GetElementPtr:
if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, I->getType(), TD))
if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
return C;
return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
}
}
/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
/// instruction (icmp/fcmp) with the specified operands. If it fails, it
/// returns a constant expression of the specified operands.
///
Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
Constant*const * Ops,
unsigned NumOps,
const TargetData *TD) {
// fold: icmp (inttoptr x), null -> icmp x, 0
// fold: icmp (ptrtoint x), 0 -> icmp x, null
// fold: icmp (inttoptr x), (inttoptr y) -> icmp x, y
// fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
//
// ConstantExpr::getCompare cannot do this, because it doesn't have TD
// around to know if bit truncation is happening.
if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && Ops[1]->isNullValue()) {
const Type *IntPtrTy = TD->getIntPtrType();
if (CE0->getOpcode() == Instruction::IntToPtr) {
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if (CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy) {
Constant *C = CE0->getOperand(0);
Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
// FIXME!
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
}
if (TD && isa<ConstantExpr>(Ops[1]) &&
cast<ConstantExpr>(Ops[1])->getOpcode() == CE0->getOpcode()) {
const Type *IntPtrTy = TD->getIntPtrType();
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if ((CE0->getOpcode() == Instruction::IntToPtr &&
CE0->getOperand(0)->getType() == IntPtrTy &&
CE0->getOperand(1)->getType() == IntPtrTy) ||
(CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy &&
CE0->getOperand(0)->getType() == CE0->getOperand(1)->getType())) {
Constant *NewOps[] = {
CE0->getOperand(0), cast<ConstantExpr>(Ops[1])->getOperand(0)
};
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
}
}
return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
}
/// 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.
@ -438,7 +499,8 @@ static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
/// with the specified arguments, returning null if unsuccessful.
Constant *
llvm::ConstantFoldCall(Function *F, Constant** Operands, unsigned NumOperands) {
llvm::ConstantFoldCall(Function *F,
Constant* const* Operands, unsigned NumOperands) {
const ValueName *NameVal = F->getValueName();
if (NameVal == 0) return 0;
const char *Str = NameVal->getKeyData();

16
lib/Analysis/ScalarEvolution.cpp
View File

@ -2043,7 +2043,12 @@ static Constant *EvaluateExpression(Value *V, Constant *PHIVal) {
if (Operands[i] == 0) return 0;
}
return ConstantFoldInstOperands(I, &Operands[0], Operands.size());
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(),
&Operands[0], Operands.size());
else
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Operands[0], Operands.size());
}
/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
@ -2213,7 +2218,14 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) {
}
}
}
Constant *C =ConstantFoldInstOperands(I, &Operands[0], Operands.size());
Constant *C;
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
C = ConstantFoldCompareInstOperands(CI->getPredicate(),
&Operands[0], Operands.size());
else
C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Operands[0], Operands.size());
return SE.getUnknown(C);
}
}

8
lib/Transforms/Utils/CloneFunction.cpp
View File

@ -299,7 +299,13 @@ ConstantFoldMappedInstruction(const Instruction *I) {
else
return 0; // All operands not constant!
return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD);
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(),
&Ops[0], Ops.size(), TD);
else
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Ops[0], Ops.size(), TD);
}
/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,

21
lib/VMCore/ConstantFold.cpp
View File

@ -985,20 +985,19 @@ static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::IntToPtr:
case Instruction::BitCast:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::PtrToInt:
// If the cast is not actually changing bits, and the second operand is a
// null pointer, do the comparison with the pre-casted value.
if (V2->isNullValue() &&
(isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
(CE1->getOpcode() == Instruction::SExt ? true :
(CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
return evaluateICmpRelation(
CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd);
bool sgnd = isSigned;
if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
return evaluateICmpRelation(CE1Op0,
Constant::getNullValue(CE1Op0->getType()),
sgnd);
}
// If the dest type is a pointer type, and the RHS is a constantexpr cast
@ -1009,11 +1008,11 @@ static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1,
if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
CE1->getOperand(0)->getType()->isInteger()) {
bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false :
(CE1->getOpcode() == Instruction::SExt ? true :
(CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
bool sgnd = isSigned;
if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0),
sgnd);
sgnd);
}
break;

3
test/Assembler/ConstantExprFold.llx
View File

@ -24,6 +24,3 @@ global bool setlt (int* getelementptr (%Ty* %B, long 0, uint 0),
int* getelementptr (%Ty* %B, long 0, uint 1)) ; true
;global bool setne (long* %A, long* cast (%Ty* %B to long*)) ; true
global bool seteq ({ short }* cast (int 1 to { short }*), { short }* null)
global bool setlt ({ short }* cast (int 1 to { short }*), { short }* cast (int 2 to { short }*))

9
test/Transforms/InstCombine/2007-12-10-ConstFoldCompare.ll Normal file
View File

@ -0,0 +1,9 @@
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
target triple = "i686-pc-linux-gnu"
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {ret i1 0}
; PR1850
define i1 @test() {
%cond = icmp ule i8* inttoptr (i64 4294967297 to i8*), inttoptr (i64 5 to i8*)
ret i1 %cond
}