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llvm-project/polly/lib/CodeGen/IslExprBuilder.cpp
Tobias Grosser 90078c5580 Add sign-extension during codegen of index expressions 
When code generating array index expressions the types of the different
components of the index expressions may not always match. We extend the type of
the index expression (if possible) and assert otherwise.

llvm-svn: 231592
2015-03-08 15:08:32 +00:00

636 lines
20 KiB
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//===------ IslExprBuilder.cpp ----- Code generate isl AST expressions ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#include "polly/CodeGen/IslExprBuilder.h"
#include "polly/ScopInfo.h"
#include "polly/Support/GICHelper.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
using namespace polly;
Type *IslExprBuilder::getWidestType(Type *T1, Type *T2) {
assert(isa<IntegerType>(T1) && isa<IntegerType>(T2));
if (T1->getPrimitiveSizeInBits() < T2->getPrimitiveSizeInBits())
return T2;
else
return T1;
}
Value *IslExprBuilder::createOpUnary(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_op_type(Expr) == isl_ast_op_minus &&
"Unsupported unary operation");
Value *V;
Type *MaxType = getType(Expr);
assert(MaxType->isIntegerTy() &&
"Unary expressions can only be created for integer types");
V = create(isl_ast_expr_get_op_arg(Expr, 0));
MaxType = getWidestType(MaxType, V->getType());
if (MaxType != V->getType())
V = Builder.CreateSExt(V, MaxType);
isl_ast_expr_free(Expr);
return Builder.CreateNSWNeg(V);
}
Value *IslExprBuilder::createOpNAry(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"isl ast expression not of type isl_ast_op");
assert(isl_ast_expr_get_op_n_arg(Expr) >= 2 &&
"We need at least two operands in an n-ary operation");
Value *V;
V = create(isl_ast_expr_get_op_arg(Expr, 0));
for (int i = 0; i < isl_ast_expr_get_op_n_arg(Expr); ++i) {
Value *OpV;
OpV = create(isl_ast_expr_get_op_arg(Expr, i));
Type *Ty = getWidestType(V->getType(), OpV->getType());
if (Ty != OpV->getType())
OpV = Builder.CreateSExt(OpV, Ty);
if (Ty != V->getType())
V = Builder.CreateSExt(V, Ty);
switch (isl_ast_expr_get_op_type(Expr)) {
default:
llvm_unreachable("This is no n-ary isl ast expression");
case isl_ast_op_max: {
Value *Cmp = Builder.CreateICmpSGT(V, OpV);
V = Builder.CreateSelect(Cmp, V, OpV);
continue;
}
case isl_ast_op_min: {
Value *Cmp = Builder.CreateICmpSLT(V, OpV);
V = Builder.CreateSelect(Cmp, V, OpV);
continue;
}
}
}
// TODO: We can truncate the result, if it fits into a smaller type. This can
// help in cases where we have larger operands (e.g. i67) but the result is
// known to fit into i64. Without the truncation, the larger i67 type may
// force all subsequent operations to be performed on a non-native type.
isl_ast_expr_free(Expr);
return V;
}
Value *IslExprBuilder::createAccessAddress(isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"isl ast expression not of type isl_ast_op");
assert(isl_ast_expr_get_op_type(Expr) == isl_ast_op_access &&
"not an access isl ast expression");
assert(isl_ast_expr_get_op_n_arg(Expr) >= 2 &&
"We need at least two operands to create a member access.");
Value *Base, *IndexOp, *Access;
isl_ast_expr *BaseExpr;
isl_id *BaseId;
BaseExpr = isl_ast_expr_get_op_arg(Expr, 0);
BaseId = isl_ast_expr_get_id(BaseExpr);
isl_ast_expr_free(BaseExpr);
const ScopArrayInfo *SAI = ScopArrayInfo::getFromId(BaseId);
Base = SAI->getBasePtr();
assert(Base->getType()->isPointerTy() && "Access base should be a pointer");
StringRef BaseName = Base->getName();
if (Base->getType() != SAI->getType())
Base = Builder.CreateBitCast(Base, SAI->getType(),
"polly.access.cast." + BaseName);
IndexOp = nullptr;
for (unsigned u = 1, e = isl_ast_expr_get_op_n_arg(Expr); u < e; u++) {
Value *NextIndex = create(isl_ast_expr_get_op_arg(Expr, u));
assert(NextIndex->getType()->isIntegerTy() &&
"Access index should be an integer");
if (!IndexOp) {
IndexOp = NextIndex;
} else {
assert(NextIndex->getType()->getScalarSizeInBits() <=
IndexOp->getType()->getScalarSizeInBits() &&
"Truncating the index type may not be save");
NextIndex = Builder.CreateIntCast(NextIndex, IndexOp->getType(), true);
IndexOp =
Builder.CreateAdd(IndexOp, NextIndex, "polly.access.add." + BaseName);
}
// For every but the last dimension multiply the size, for the last
// dimension we can exit the loop.
if (u + 1 >= e)
break;
const SCEV *DimSCEV = SAI->getDimensionSize(u - 1);
Value *DimSize = Expander.expandCodeFor(DimSCEV, DimSCEV->getType(),
Builder.GetInsertPoint());
Type *Ty = getWidestType(DimSize->getType(), IndexOp->getType());
if (Ty != IndexOp->getType())
IndexOp = Builder.CreateSExtOrTrunc(IndexOp, Ty,
"polly.access.sext." + BaseName);
IndexOp =
Builder.CreateMul(IndexOp, DimSize, "polly.access.mul." + BaseName);
}
Access = Builder.CreateGEP(Base, IndexOp, "polly.access." + BaseName);
isl_ast_expr_free(Expr);
return Access;
}
Value *IslExprBuilder::createOpAccess(isl_ast_expr *Expr) {
Value *Addr = createAccessAddress(Expr);
assert(Addr && "Could not create op access address");
return Builder.CreateLoad(Addr, Addr->getName() + ".load");
}
Value *IslExprBuilder::createOpBin(__isl_take isl_ast_expr *Expr) {
Value *LHS, *RHS, *Res;
Type *MaxType;
isl_ast_expr *LOp, *ROp;
isl_ast_op_type OpType;
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"isl ast expression not of type isl_ast_op");
assert(isl_ast_expr_get_op_n_arg(Expr) == 2 &&
"not a binary isl ast expression");
OpType = isl_ast_expr_get_op_type(Expr);
LOp = isl_ast_expr_get_op_arg(Expr, 0);
ROp = isl_ast_expr_get_op_arg(Expr, 1);
// Catch the special case ((-<pointer>) + <pointer>) which is for
// isl the same as (<pointer> - <pointer>). We have to treat it here because
// there is no valid semantics for the (-<pointer>) expression, hence in
// createOpUnary such an expression will trigger a crash.
// FIXME: The same problem can now be triggered by a subexpression of the LHS,
// however it is much less likely.
if (OpType == isl_ast_op_add &&
isl_ast_expr_get_type(LOp) == isl_ast_expr_op &&
isl_ast_expr_get_op_type(LOp) == isl_ast_op_minus) {
// Change the binary addition to a substraction.
OpType = isl_ast_op_sub;
// Extract the unary operand of the LHS.
auto *LOpOp = isl_ast_expr_get_op_arg(LOp, 0);
isl_ast_expr_free(LOp);
// Swap the unary operand of the LHS and the RHS.
LOp = ROp;
ROp = LOpOp;
}
LHS = create(LOp);
RHS = create(ROp);
Type *LHSType = LHS->getType();
Type *RHSType = RHS->getType();
// Handle <pointer> - <pointer>
if (LHSType->isPointerTy() && RHSType->isPointerTy()) {
isl_ast_expr_free(Expr);
assert(OpType == isl_ast_op_sub && "Substraction is the only valid binary "
"pointer <-> pointer operation.");
return Builder.CreatePtrDiff(LHS, RHS);
}
// Handle <pointer> +/- <integer> and <integer> +/- <pointer>
if (LHSType->isPointerTy() || RHSType->isPointerTy()) {
isl_ast_expr_free(Expr);
assert((LHSType->isIntegerTy() || RHSType->isIntegerTy()) &&
"Arithmetic operations might only performed on one but not two "
"pointer types.");
if (LHSType->isIntegerTy())
std::swap(LHS, RHS);
switch (OpType) {
default:
llvm_unreachable(
"Only additive binary operations are allowed on pointer types.");
case isl_ast_op_sub:
RHS = Builder.CreateNeg(RHS);
// Fall through
case isl_ast_op_add:
return Builder.CreateGEP(LHS, RHS);
}
}
MaxType = getWidestType(LHSType, RHSType);
// Take the result into account when calculating the widest type.
//
// For operations such as '+' the result may require a type larger than
// the type of the individual operands. For other operations such as '/', the
// result type cannot be larger than the type of the individual operand. isl
// does not calculate correct types for these operations and we consequently
// exclude those operations here.
switch (OpType) {
case isl_ast_op_pdiv_q:
case isl_ast_op_pdiv_r:
case isl_ast_op_div:
case isl_ast_op_fdiv_q:
case isl_ast_op_zdiv_r:
// Do nothing
break;
case isl_ast_op_add:
case isl_ast_op_sub:
case isl_ast_op_mul:
MaxType = getWidestType(MaxType, getType(Expr));
break;
default:
llvm_unreachable("This is no binary isl ast expression");
}
if (MaxType != RHS->getType())
RHS = Builder.CreateSExt(RHS, MaxType);
if (MaxType != LHS->getType())
LHS = Builder.CreateSExt(LHS, MaxType);
switch (OpType) {
default:
llvm_unreachable("This is no binary isl ast expression");
case isl_ast_op_add:
Res = Builder.CreateNSWAdd(LHS, RHS);
break;
case isl_ast_op_sub:
Res = Builder.CreateNSWSub(LHS, RHS);
break;
case isl_ast_op_mul:
Res = Builder.CreateNSWMul(LHS, RHS);
break;
case isl_ast_op_div:
case isl_ast_op_pdiv_q: // Dividend is non-negative
Res = Builder.CreateSDiv(LHS, RHS);
break;
case isl_ast_op_fdiv_q: { // Round towards -infty
// TODO: Review code and check that this calculation does not yield
// incorrect overflow in some bordercases.
//
// floord(n,d) ((n < 0) ? (n - d + 1) : n) / d
Value *One = ConstantInt::get(MaxType, 1);
Value *Zero = ConstantInt::get(MaxType, 0);
Value *Sum1 = Builder.CreateSub(LHS, RHS);
Value *Sum2 = Builder.CreateAdd(Sum1, One);
Value *isNegative = Builder.CreateICmpSLT(LHS, Zero);
Value *Dividend = Builder.CreateSelect(isNegative, Sum2, LHS);
Res = Builder.CreateSDiv(Dividend, RHS);
break;
}
case isl_ast_op_pdiv_r: // Dividend is non-negative
case isl_ast_op_zdiv_r: // Result only compared against zero
Res = Builder.CreateSRem(LHS, RHS);
break;
}
// TODO: We can truncate the result, if it fits into a smaller type. This can
// help in cases where we have larger operands (e.g. i67) but the result is
// known to fit into i64. Without the truncation, the larger i67 type may
// force all subsequent operations to be performed on a non-native type.
isl_ast_expr_free(Expr);
return Res;
}
Value *IslExprBuilder::createOpSelect(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_op_type(Expr) == isl_ast_op_select &&
"Unsupported unary isl ast expression");
Value *LHS, *RHS, *Cond;
Type *MaxType = getType(Expr);
Cond = create(isl_ast_expr_get_op_arg(Expr, 0));
if (!Cond->getType()->isIntegerTy(1))
Cond = Builder.CreateIsNotNull(Cond);
LHS = create(isl_ast_expr_get_op_arg(Expr, 1));
RHS = create(isl_ast_expr_get_op_arg(Expr, 2));
MaxType = getWidestType(MaxType, LHS->getType());
MaxType = getWidestType(MaxType, RHS->getType());
if (MaxType != RHS->getType())
RHS = Builder.CreateSExt(RHS, MaxType);
if (MaxType != LHS->getType())
LHS = Builder.CreateSExt(LHS, MaxType);
// TODO: Do we want to truncate the result?
isl_ast_expr_free(Expr);
return Builder.CreateSelect(Cond, LHS, RHS);
}
Value *IslExprBuilder::createOpICmp(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expected an isl_ast_expr_op expression");
Value *LHS, *RHS, *Res;
LHS = create(isl_ast_expr_get_op_arg(Expr, 0));
RHS = create(isl_ast_expr_get_op_arg(Expr, 1));
bool IsPtrType =
LHS->getType()->isPointerTy() || RHS->getType()->isPointerTy();
if (LHS->getType() != RHS->getType()) {
if (IsPtrType) {
Type *I8PtrTy = Builder.getInt8PtrTy();
if (!LHS->getType()->isPointerTy())
LHS = Builder.CreateIntToPtr(LHS, I8PtrTy);
if (!RHS->getType()->isPointerTy())
RHS = Builder.CreateIntToPtr(RHS, I8PtrTy);
if (LHS->getType() != I8PtrTy)
LHS = Builder.CreateBitCast(LHS, I8PtrTy);
if (RHS->getType() != I8PtrTy)
RHS = Builder.CreateBitCast(RHS, I8PtrTy);
} else {
Type *MaxType = LHS->getType();
MaxType = getWidestType(MaxType, RHS->getType());
if (MaxType != RHS->getType())
RHS = Builder.CreateSExt(RHS, MaxType);
if (MaxType != LHS->getType())
LHS = Builder.CreateSExt(LHS, MaxType);
}
}
isl_ast_op_type OpType = isl_ast_expr_get_op_type(Expr);
assert(OpType >= isl_ast_op_eq && OpType <= isl_ast_op_gt &&
"Unsupported ICmp isl ast expression");
assert(isl_ast_op_eq + 4 == isl_ast_op_gt &&
"Isl ast op type interface changed");
CmpInst::Predicate Predicates[5][2] = {
{CmpInst::ICMP_EQ, CmpInst::ICMP_EQ},
{CmpInst::ICMP_SLE, CmpInst::ICMP_ULE},
{CmpInst::ICMP_SLT, CmpInst::ICMP_ULT},
{CmpInst::ICMP_SGE, CmpInst::ICMP_UGE},
{CmpInst::ICMP_SGT, CmpInst::ICMP_UGT},
};
Res = Builder.CreateICmp(Predicates[OpType - isl_ast_op_eq][IsPtrType], LHS,
RHS);
isl_ast_expr_free(Expr);
return Res;
}
Value *IslExprBuilder::createOpBoolean(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expected an isl_ast_expr_op expression");
Value *LHS, *RHS, *Res;
isl_ast_op_type OpType;
OpType = isl_ast_expr_get_op_type(Expr);
assert((OpType == isl_ast_op_and || OpType == isl_ast_op_or) &&
"Unsupported isl_ast_op_type");
LHS = create(isl_ast_expr_get_op_arg(Expr, 0));
RHS = create(isl_ast_expr_get_op_arg(Expr, 1));
// Even though the isl pretty printer prints the expressions as 'exp && exp'
// or 'exp || exp', we actually code generate the bitwise expressions
// 'exp & exp' or 'exp | exp'. This forces the evaluation of both branches,
// but it is, due to the use of i1 types, otherwise equivalent. The reason
// to go for bitwise operations is, that we assume the reduced control flow
// will outweight the overhead introduced by evaluating unneeded expressions.
// The isl code generation currently does not take advantage of the fact that
// the expression after an '||' or '&&' is in some cases not evaluated.
// Evaluating it anyways does not cause any undefined behaviour.
//
// TODO: Document in isl itself, that the unconditionally evaluating the
// second part of '||' or '&&' expressions is safe.
if (!LHS->getType()->isIntegerTy(1))
LHS = Builder.CreateIsNotNull(LHS);
if (!RHS->getType()->isIntegerTy(1))
RHS = Builder.CreateIsNotNull(RHS);
switch (OpType) {
default:
llvm_unreachable("Unsupported boolean expression");
case isl_ast_op_and:
Res = Builder.CreateAnd(LHS, RHS);
break;
case isl_ast_op_or:
Res = Builder.CreateOr(LHS, RHS);
break;
}
isl_ast_expr_free(Expr);
return Res;
}
Value *
IslExprBuilder::createOpBooleanConditional(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expected an isl_ast_expr_op expression");
Value *LHS, *RHS;
isl_ast_op_type OpType;
Function *F = Builder.GetInsertBlock()->getParent();
LLVMContext &Context = F->getContext();
OpType = isl_ast_expr_get_op_type(Expr);
assert((OpType == isl_ast_op_and_then || OpType == isl_ast_op_or_else) &&
"Unsupported isl_ast_op_type");
auto InsertBB = Builder.GetInsertBlock();
auto InsertPoint = Builder.GetInsertPoint();
auto NextBB = SplitBlock(InsertBB, InsertPoint, &DT, &LI);
BasicBlock *CondBB = BasicBlock::Create(Context, "polly.cond", F);
LI.changeLoopFor(CondBB, LI.getLoopFor(InsertBB));
DT.addNewBlock(CondBB, InsertBB);
InsertBB->getTerminator()->eraseFromParent();
Builder.SetInsertPoint(InsertBB);
auto BR = Builder.CreateCondBr(Builder.getTrue(), NextBB, CondBB);
Builder.SetInsertPoint(CondBB);
Builder.CreateBr(NextBB);
Builder.SetInsertPoint(InsertBB->getTerminator());
LHS = create(isl_ast_expr_get_op_arg(Expr, 0));
if (!LHS->getType()->isIntegerTy(1))
LHS = Builder.CreateIsNotNull(LHS);
auto LeftBB = Builder.GetInsertBlock();
if (OpType == isl_ast_op_and || OpType == isl_ast_op_and_then)
BR->setCondition(Builder.CreateNeg(LHS));
else
BR->setCondition(LHS);
Builder.SetInsertPoint(CondBB->getTerminator());
RHS = create(isl_ast_expr_get_op_arg(Expr, 1));
if (!RHS->getType()->isIntegerTy(1))
RHS = Builder.CreateIsNotNull(RHS);
auto RightBB = Builder.GetInsertBlock();
Builder.SetInsertPoint(NextBB->getTerminator());
auto PHI = Builder.CreatePHI(Builder.getInt1Ty(), 2);
PHI->addIncoming(OpType == isl_ast_op_and_then ? Builder.getFalse()
: Builder.getTrue(),
LeftBB);
PHI->addIncoming(RHS, RightBB);
isl_ast_expr_free(Expr);
return PHI;
}
Value *IslExprBuilder::createOp(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expression not of type isl_ast_expr_op");
switch (isl_ast_expr_get_op_type(Expr)) {
case isl_ast_op_error:
case isl_ast_op_cond:
case isl_ast_op_call:
case isl_ast_op_member:
llvm_unreachable("Unsupported isl ast expression");
case isl_ast_op_access:
return createOpAccess(Expr);
case isl_ast_op_max:
case isl_ast_op_min:
return createOpNAry(Expr);
case isl_ast_op_add:
case isl_ast_op_sub:
case isl_ast_op_mul:
case isl_ast_op_div:
case isl_ast_op_fdiv_q: // Round towards -infty
case isl_ast_op_pdiv_q: // Dividend is non-negative
case isl_ast_op_pdiv_r: // Dividend is non-negative
case isl_ast_op_zdiv_r: // Result only compared against zero
return createOpBin(Expr);
case isl_ast_op_minus:
return createOpUnary(Expr);
case isl_ast_op_select:
return createOpSelect(Expr);
case isl_ast_op_and:
case isl_ast_op_or:
return createOpBoolean(Expr);
case isl_ast_op_and_then:
case isl_ast_op_or_else:
return createOpBooleanConditional(Expr);
case isl_ast_op_eq:
case isl_ast_op_le:
case isl_ast_op_lt:
case isl_ast_op_ge:
case isl_ast_op_gt:
return createOpICmp(Expr);
case isl_ast_op_address_of:
return createOpAddressOf(Expr);
}
llvm_unreachable("Unsupported isl_ast_expr_op kind.");
}
Value *IslExprBuilder::createOpAddressOf(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expected an isl_ast_expr_op expression.");
assert(isl_ast_expr_get_op_n_arg(Expr) == 1 && "Address of should be unary.");
isl_ast_expr *Op = isl_ast_expr_get_op_arg(Expr, 0);
assert(isl_ast_expr_get_type(Op) == isl_ast_expr_op &&
"Expected address of operator to be an isl_ast_expr_op expression.");
assert(isl_ast_expr_get_op_type(Op) == isl_ast_op_access &&
"Expected address of operator to be an access expression.");
Value *V = createAccessAddress(Op);
isl_ast_expr_free(Expr);
return V;
}
Value *IslExprBuilder::createId(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_id &&
"Expression not of type isl_ast_expr_ident");
isl_id *Id;
Value *V;
Id = isl_ast_expr_get_id(Expr);
assert(IDToValue.count(Id) && "Identifier not found");
V = IDToValue[Id];
isl_id_free(Id);
isl_ast_expr_free(Expr);
return V;
}
IntegerType *IslExprBuilder::getType(__isl_keep isl_ast_expr *Expr) {
// XXX: We assume i64 is large enough. This is often true, but in general
// incorrect. Also, on 32bit architectures, it would be beneficial to
// use a smaller type. We can and should directly derive this information
// during code generation.
return IntegerType::get(Builder.getContext(), 64);
}
Value *IslExprBuilder::createInt(__isl_take isl_ast_expr *Expr) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_int &&
"Expression not of type isl_ast_expr_int");
isl_val *Val;
Value *V;
APInt APValue;
IntegerType *T;
Val = isl_ast_expr_get_val(Expr);
APValue = APIntFromVal(Val);
T = getType(Expr);
APValue = APValue.sextOrSelf(T->getBitWidth());
V = ConstantInt::get(T, APValue);
isl_ast_expr_free(Expr);
return V;
}
Value *IslExprBuilder::create(__isl_take isl_ast_expr *Expr) {
switch (isl_ast_expr_get_type(Expr)) {
case isl_ast_expr_error:
llvm_unreachable("Code generation error");
case isl_ast_expr_op:
return createOp(Expr);
case isl_ast_expr_id:
return createId(Expr);
case isl_ast_expr_int:
return createInt(Expr);
}
llvm_unreachable("Unexpected enum value");
}
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