[polly] r214220 - [Refactor] Expose the IslExprBuilder (missing files)
Johannes Doerfert
jdoerfert at codeaurora.org
Tue Jul 29 14:06:08 PDT 2014
Author: jdoerfert
Date: Tue Jul 29 16:06:08 2014
New Revision: 214220
URL: http://llvm.org/viewvc/llvm-project?rev=214220&view=rev
Log:
[Refactor] Expose the IslExprBuilder (missing files)
Added:
polly/trunk/include/polly/CodeGen/IslExprBuilder.h
polly/trunk/lib/CodeGen/IslExprBuilder.cpp
Added: polly/trunk/include/polly/CodeGen/IslExprBuilder.h
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/include/polly/CodeGen/IslExprBuilder.h?rev=214220&view=auto
==============================================================================
--- polly/trunk/include/polly/CodeGen/IslExprBuilder.h (added)
+++ polly/trunk/include/polly/CodeGen/IslExprBuilder.h Tue Jul 29 16:06:08 2014
@@ -0,0 +1,133 @@
+//===-IslExprBuilder.h - Helper to generate code for isl AST expressions --===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef POLLY_ISL_EXPR_BUILDER_H
+#define POLLY_ISL_EXPR_BUILDER_H
+
+#include "polly/CodeGen/IRBuilder.h"
+
+#include "isl/ast.h"
+
+#include <map>
+
+namespace polly {
+
+/// @brief LLVM-IR generator for isl_ast_expr[essions]
+///
+/// This generator generates LLVM-IR that performs the computation described by
+/// an isl_ast_expr[ession].
+///
+/// Example:
+///
+/// An isl_ast_expr[ession] can look like this:
+///
+/// (N + M) + 10
+///
+/// The IslExprBuilder could create the following LLVM-IR:
+///
+/// %tmp1 = add nsw i64 %N
+/// %tmp2 = add nsw i64 %tmp1, %M
+/// %tmp3 = add nsw i64 %tmp2, 10
+///
+/// The implementation of this class is mostly a mapping from isl_ast_expr
+/// constructs to the corresponding LLVM-IR constructs.
+///
+/// The following decisions may need some explanation:
+///
+/// 1) Which data-type to choose
+///
+/// isl_ast_expr[essions] are untyped expressions that assume arbitrary
+/// precision integer computations. LLVM-IR instead has fixed size integers.
+/// When lowering to LLVM-IR we need to chose both the size of the data type and
+/// the sign of the operations we use.
+///
+/// At the moment, we hardcode i64 bit signed computations. Our experience has
+/// shown that 64 bit are generally large enough for the loop bounds that appear
+/// in the wild. Signed computations are needed, as loop bounds may become
+/// negative.
+///
+/// FIXME: Hardcoding sizes can cause issues:
+///
+/// a) Certain run-time checks that we may want to generate can involve the
+/// size of the data types the computation is performed on. When code
+/// generating these run-time checks to isl_ast_expr[essions], the
+/// resulting computation may require more than 64 bit.
+///
+/// b) On embedded systems and especially for high-level-synthesis 64 bit
+/// computations are very costly.
+///
+/// The right approach is to compute the minimal necessary bitwidth and
+/// signedness for each subexpression during in the isl AST generation and
+/// to use this information in our IslAstGenerator. Preliminary patches are
+/// available, but have not been committed yet.
+///
+/// 2) We always flag computations with 'nsw'
+///
+/// As isl_ast_expr[essions] assume arbitrary precision, no wrapping should
+/// ever occur in the generated LLVM-IR (assuming the data type chosen is large
+/// enough).
+class IslExprBuilder {
+public:
+ /// @brief Construct an IslExprBuilder.
+ ///
+ /// @param Builder The IRBuilder used to construct the isl_ast_expr[ession].
+ /// The insert location of this IRBuilder defines WHERE the
+ /// corresponding LLVM-IR is generated.
+ ///
+ /// @param IDToValue The isl_ast_expr[ession] may reference parameters or
+ /// variables (identified by an isl_id). The IDTOValue map
+ /// specifies the LLVM-IR Values that correspond to these
+ /// parameters and variables.
+ IslExprBuilder(PollyIRBuilder &Builder,
+ std::map<isl_id *, llvm::Value *> &IDToValue)
+ : Builder(Builder), IDToValue(IDToValue) {}
+
+ /// @brief Create LLVM-IR for an isl_ast_expr[ession].
+ ///
+ /// @param Expr The ast expression for which we generate LLVM-IR.
+ ///
+ /// @return The llvm::Value* containing the result of the computation.
+ llvm::Value *create(__isl_take isl_ast_expr *Expr);
+
+ /// @brief Return the largest of two types.
+ ///
+ /// @param T1 The first type.
+ /// @param T2 The second type.
+ ///
+ /// @return The largest of the two types.
+ llvm::Type *getWidestType(llvm::Type *T1, llvm::Type *T2);
+
+ /// @brief Return the type with which this expression should be computed.
+ ///
+ /// The type needs to be large enough to hold all possible input and all
+ /// possible output values.
+ ///
+ /// @param Expr The expression for which to find the type.
+ /// @return The type with which the expression should be computed.
+ llvm::IntegerType *getType(__isl_keep isl_ast_expr *Expr);
+
+private:
+ PollyIRBuilder &Builder;
+ std::map<isl_id *, llvm::Value *> &IDToValue;
+
+ llvm::Value *createOp(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpUnary(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpBin(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpNAry(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpSelect(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpICmp(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createOpBoolean(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createId(__isl_take isl_ast_expr *Expr);
+ llvm::Value *createInt(__isl_take isl_ast_expr *Expr);
+};
+}
+
+#endif
Added: polly/trunk/lib/CodeGen/IslExprBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/CodeGen/IslExprBuilder.cpp?rev=214220&view=auto
==============================================================================
--- polly/trunk/lib/CodeGen/IslExprBuilder.cpp (added)
+++ polly/trunk/lib/CodeGen/IslExprBuilder.cpp Tue Jul 29 16:06:08 2014
@@ -0,0 +1,395 @@
+//===------ 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/Support/GICHelper.h"
+
+#include "llvm/Support/Debug.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);
+
+ 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::createOpBin(__isl_take isl_ast_expr *Expr) {
+ Value *LHS, *RHS, *Res;
+ Type *MaxType;
+ 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);
+
+ LHS = create(isl_ast_expr_get_op_arg(Expr, 0));
+ RHS = create(isl_ast_expr_get_op_arg(Expr, 1));
+
+ MaxType = LHS->getType();
+ MaxType = getWidestType(MaxType, RHS->getType());
+
+ // 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:
+ // 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
+ 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));
+
+ 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));
+
+ 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);
+
+ switch (isl_ast_expr_get_op_type(Expr)) {
+ default:
+ llvm_unreachable("Unsupported ICmp isl ast expression");
+ case isl_ast_op_eq:
+ Res = Builder.CreateICmpEQ(LHS, RHS);
+ break;
+ case isl_ast_op_le:
+ Res = Builder.CreateICmpSLE(LHS, RHS);
+ break;
+ case isl_ast_op_lt:
+ Res = Builder.CreateICmpSLT(LHS, RHS);
+ break;
+ case isl_ast_op_ge:
+ Res = Builder.CreateICmpSGE(LHS, RHS);
+ break;
+ case isl_ast_op_gt:
+ Res = Builder.CreateICmpSGT(LHS, RHS);
+ break;
+ }
+
+ 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.
+ assert(LHS->getType() == Builder.getInt1Ty() && "Expected i1 type");
+ assert(RHS->getType() == Builder.getInt1Ty() && "Expected i1 type");
+
+ 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::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_and_then:
+ case isl_ast_op_or_else:
+ case isl_ast_op_call:
+ case isl_ast_op_member:
+ case isl_ast_op_access:
+ llvm_unreachable("Unsupported isl ast expression");
+ 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
+ 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_eq:
+ case isl_ast_op_le:
+ case isl_ast_op_lt:
+ case isl_ast_op_ge:
+ case isl_ast_op_gt:
+ return createOpICmp(Expr);
+ }
+
+ llvm_unreachable("Unsupported isl_ast_expr_op kind.");
+}
+
+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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