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Fix CodeGen of pointer arithmetic in compound assignment statements. 

- Changed EmitSub to work on all cases (arithmetic, ptr - int, ptr -
   ptr) so that implementation matches that of other operators.

 - Modify EmitCompoundAssign to compute and perform the appropriate
   casts of left, right, and result types for the assorted pointer
   arithmetic cases.

 - Fix EmitSub (ptr - int) case to negate the rhs *after*
   extension. This is critical when the rhs is unsigned (and needs
   extension).

 - This fixes cfrac.

 - <rdr://6115726>

llvm-svn: 54392
This commit is contained in:
Daniel Dunbar 2008-08-06 02:00:38 +00:00
parent 0e966d3e2c
commit bfb1cd7454
2 changed files with 118 additions and 75 deletions
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168
clang/lib/CodeGen/CGExprScalar.cpp
View File

@ -264,18 +264,14 @@ public:
HANDLEBINOP(Div);
HANDLEBINOP(Rem);
HANDLEBINOP(Add);
// (Sub) - Sub is handled specially below for ptr-ptr subtract.
HANDLEBINOP(Sub);
HANDLEBINOP(Shl);
HANDLEBINOP(Shr);
HANDLEBINOP(And);
HANDLEBINOP(Xor);
HANDLEBINOP(Or);
#undef HANDLEBINOP
Value *VisitBinSub(const BinaryOperator *E);
Value *VisitBinSubAssign(const CompoundAssignOperator *E) {
return EmitCompoundAssign(E, &ScalarExprEmitter::EmitSub);
}
// Comparisons.
Value *EmitCompare(const BinaryOperator *E, unsigned UICmpOpc,
unsigned SICmpOpc, unsigned FCmpOpc);
@ -751,26 +747,56 @@ Value *ScalarExprEmitter::EmitCompoundAssign(const CompoundAssignOperator *E,
OpInfo.RHS = Visit(E->getRHS());
}
// Convert the LHS/RHS values to the computation type.
OpInfo.LHS = EmitScalarConversion(OpInfo.LHS, LHSTy, ComputeType);
// Do not merge types for -= or += where the LHS is a pointer.
if (!(E->getOpcode() == BinaryOperator::SubAssign ||
E->getOpcode() == BinaryOperator::AddAssign) ||
!E->getLHS()->getType()->isPointerType()) {
OpInfo.RHS = EmitScalarConversion(OpInfo.RHS, RHSTy, ComputeType);
QualType LComputeTy, RComputeTy, ResultTy;
// Compound assignment does not contain enough information about all
// the types involved for pointer arithmetic cases. Figure it out
// here for now.
if (E->getLHS()->getType()->isPointerType()) {
// Pointer arithmetic cases: ptr +=,-= int and ptr -= ptr,
assert((E->getOpcode() == BinaryOperator::AddAssign ||
E->getOpcode() == BinaryOperator::SubAssign) &&
"Invalid compound assignment operator on pointer type.");
LComputeTy = E->getLHS()->getType();
if (E->getRHS()->getType()->isPointerType()) {
// Degenerate case of (ptr -= ptr) allowed by GCC implicit cast
// extension, the conversion from the pointer difference back to
// the LHS type is handled at the end.
assert(E->getOpcode() == BinaryOperator::SubAssign &&
"Invalid compound assignment operator on pointer type.");
RComputeTy = E->getLHS()->getType();
ResultTy = CGF.getContext().getPointerDiffType();
} else {
RComputeTy = E->getRHS()->getType();
ResultTy = LComputeTy;
}
} else if (E->getRHS()->getType()->isPointerType()) {
// Degenerate case of (int += ptr) allowed by GCC implicit cast
// extension.
assert(E->getOpcode() == BinaryOperator::AddAssign &&
"Invalid compound assignment operator on pointer type.");
LComputeTy = E->getLHS()->getType();
RComputeTy = E->getRHS()->getType();
ResultTy = RComputeTy;
} else {
LComputeTy = RComputeTy = ResultTy = ComputeType;
}
OpInfo.Ty = ComputeType;
// Convert the LHS/RHS values to the computation type.
OpInfo.LHS = EmitScalarConversion(OpInfo.LHS, LHSTy, LComputeTy);
OpInfo.RHS = EmitScalarConversion(OpInfo.RHS, RHSTy, RComputeTy);
OpInfo.Ty = ResultTy;
OpInfo.E = E;
// Expand the binary operator.
Value *Result = (this->*Func)(OpInfo);
// Truncate the result back to the LHS type.
Result = EmitScalarConversion(Result, ComputeType, LHSTy);
// Convert the result back to the LHS type.
Result = EmitScalarConversion(Result, ResultTy, LHSTy);
// Store the result value into the LHS lvalue.
CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV, E->getType());
CGF.EmitStoreThroughLValue(RValue::get(Result), LHSLV, LHSTy);
// For bitfields, we need the value in the bitfield
// FIXME: This adds an extra bitfield load
@ -833,70 +859,62 @@ Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &Ops) {
Value *ScalarExprEmitter::EmitSub(const BinOpInfo &Ops) {
if (!isa<llvm::PointerType>(Ops.LHS->getType()))
return Builder.CreateSub(Ops.LHS, Ops.RHS, "sub");
// pointer - int
assert(!isa<llvm::PointerType>(Ops.RHS->getType()) &&
"ptr-ptr shouldn't get here");
// FIXME: The pointer could point to a VLA.
Value *Idx = Builder.CreateNeg(Ops.RHS, "sub.ptr.neg");
unsigned Width = cast<llvm::IntegerType>(Idx->getType())->getBitWidth();
if (Width < CGF.LLVMPointerWidth) {
// Zero or sign extend the pointer value based on whether the index is
// signed or not.
const llvm::Type *IdxType = llvm::IntegerType::get(CGF.LLVMPointerWidth);
if (Ops.E->getRHS()->getType()->isSignedIntegerType())
Idx = Builder.CreateSExt(Idx, IdxType, "idx.ext");
else
Idx = Builder.CreateZExt(Idx, IdxType, "idx.ext");
}
// The GNU void* - int case is automatically handled here because
// our LLVM type for void* is i8*.
return Builder.CreateGEP(Ops.LHS, Idx, "sub.ptr");
}
Value *ScalarExprEmitter::VisitBinSub(const BinaryOperator *E) {
// "X - Y" is different from "X -= Y" in one case: when Y is a pointer. In
// the compound assignment case it is invalid, so just handle it here.
if (!E->getRHS()->getType()->isPointerType())
return EmitSub(EmitBinOps(E));
// pointer - pointer
Value *LHS = Visit(E->getLHS());
Value *RHS = Visit(E->getRHS());
const QualType LHSType = E->getLHS()->getType();
const QualType LHSElementType = LHSType->getAsPointerType()->getPointeeType();
uint64_t ElementSize;
// Handle GCC extension for pointer arithmetic on void* types.
if (LHSElementType->isVoidType()) {
ElementSize = 1;
if (!isa<llvm::PointerType>(Ops.RHS->getType())) {
// pointer - int
Value *Idx = Ops.RHS;
unsigned Width = cast<llvm::IntegerType>(Idx->getType())->getBitWidth();
if (Width < CGF.LLVMPointerWidth) {
// Zero or sign extend the pointer value based on whether the index is
// signed or not.
const llvm::Type *IdxType = llvm::IntegerType::get(CGF.LLVMPointerWidth);
if (Ops.E->getRHS()->getType()->isSignedIntegerType())
Idx = Builder.CreateSExt(Idx, IdxType, "idx.ext");
else
Idx = Builder.CreateZExt(Idx, IdxType, "idx.ext");
}
Idx = Builder.CreateNeg(Idx, "sub.ptr.neg");
// FIXME: The pointer could point to a VLA.
// The GNU void* - int case is automatically handled here because
// our LLVM type for void* is i8*.
return Builder.CreateGEP(Ops.LHS, Idx, "sub.ptr");
} else {
ElementSize = CGF.getContext().getTypeSize(LHSElementType) / 8;
}
// pointer - pointer
Value *LHS = Ops.LHS;
Value *RHS = Ops.RHS;
const llvm::Type *ResultType = ConvertType(E->getType());
LHS = Builder.CreatePtrToInt(LHS, ResultType, "sub.ptr.lhs.cast");
RHS = Builder.CreatePtrToInt(RHS, ResultType, "sub.ptr.rhs.cast");
Value *BytesBetween = Builder.CreateSub(LHS, RHS, "sub.ptr.sub");
const QualType LHSType = Ops.E->getLHS()->getType();
const QualType LHSElementType = LHSType->getAsPointerType()->getPointeeType();
uint64_t ElementSize;
// HACK: LLVM doesn't have an divide instruction that 'knows' there is no
// remainder. As such, we handle common power-of-two cases here to generate
// better code.
if (llvm::isPowerOf2_64(ElementSize)) {
Value *ShAmt =
llvm::ConstantInt::get(ResultType, llvm::Log2_64(ElementSize));
return Builder.CreateAShr(BytesBetween, ShAmt, "sub.ptr.shr");
// Handle GCC extension for pointer arithmetic on void* types.
if (LHSElementType->isVoidType()) {
ElementSize = 1;
} else {
ElementSize = CGF.getContext().getTypeSize(LHSElementType) / 8;
}
const llvm::Type *ResultType = ConvertType(Ops.Ty);
LHS = Builder.CreatePtrToInt(LHS, ResultType, "sub.ptr.lhs.cast");
RHS = Builder.CreatePtrToInt(RHS, ResultType, "sub.ptr.rhs.cast");
Value *BytesBetween = Builder.CreateSub(LHS, RHS, "sub.ptr.sub");
// HACK: LLVM doesn't have an divide instruction that 'knows' there is no
// remainder. As such, we handle common power-of-two cases here to generate
// better code. See PR2247.
if (llvm::isPowerOf2_64(ElementSize)) {
Value *ShAmt =
llvm::ConstantInt::get(ResultType, llvm::Log2_64(ElementSize));
return Builder.CreateAShr(BytesBetween, ShAmt, "sub.ptr.shr");
}
// Otherwise, do a full sdiv.
Value *BytesPerElt = llvm::ConstantInt::get(ResultType, ElementSize);
return Builder.CreateSDiv(BytesBetween, BytesPerElt, "sub.ptr.div");
}
// Otherwise, do a full sdiv.
Value *BytesPerElt = llvm::ConstantInt::get(ResultType, ElementSize);
return Builder.CreateSDiv(BytesBetween, BytesPerElt, "sub.ptr.div");
}
Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
// LLVM requires the LHS and RHS to be the same type: promote or truncate the
// RHS to the same size as the LHS.

25
clang/test/CodeGen/2008-07-31-promotion-of-compound-pointer-arithmetic.c Normal file
View File

@ -0,0 +1,25 @@
// RUN: clang -emit-llvm-bc -o - %s | opt -std-compile-opts | llvm-dis | grep "ret i32 1" | count 3
// <rdr://6115726>
int f0() {
int x;
unsigned short n = 1;
int *a = &x;
int *b = &x;
a = a - n;
b -= n;
return a == b;
}
int f1(int *a) {
int b = a - (int*) 1;
a -= (int*) 1;
return b == (int) a;
}
int f2(int n) {
int *b = n + (int*) 1;
n += (int*) 1;
return b == (int*) n;
}