1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Emit OpenACC Loop Stmt node as CIR code.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "CIRGenBuilder.h"
14 #include "CIRGenFunction.h"
15
16 #include "clang/AST/StmtOpenACC.h"
17
18 #include "mlir/Dialect/OpenACC/OpenACC.h"
19
20 using namespace clang;
21 using namespace clang::CIRGen;
22 using namespace cir;
23 using namespace mlir::acc;
24
updateLoopOpParallelism(mlir::acc::LoopOp & op,bool isOrphan,OpenACCDirectiveKind dk)25 void CIRGenFunction::updateLoopOpParallelism(mlir::acc::LoopOp &op,
26 bool isOrphan,
27 OpenACCDirectiveKind dk) {
28 // Check that at least one of auto, independent, or seq is present
29 // for the device-independent default clauses.
30 if (op.hasParallelismFlag(mlir::acc::DeviceType::None))
31 return;
32
33 switch (dk) {
34 default:
35 llvm_unreachable("Invalid parent directive kind");
36 case OpenACCDirectiveKind::Invalid:
37 case OpenACCDirectiveKind::Parallel:
38 case OpenACCDirectiveKind::ParallelLoop:
39 op.addIndependent(builder.getContext(), {});
40 return;
41 case OpenACCDirectiveKind::Kernels:
42 case OpenACCDirectiveKind::KernelsLoop:
43 op.addAuto(builder.getContext(), {});
44 return;
45 case OpenACCDirectiveKind::Serial:
46 case OpenACCDirectiveKind::SerialLoop:
47 if (op.hasDefaultGangWorkerVector())
48 op.addAuto(builder.getContext(), {});
49 else
50 op.addSeq(builder.getContext(), {});
51 return;
52 };
53 }
54
55 mlir::LogicalResult
emitOpenACCLoopConstruct(const OpenACCLoopConstruct & s)56 CIRGenFunction::emitOpenACCLoopConstruct(const OpenACCLoopConstruct &s) {
57 mlir::Location start = getLoc(s.getSourceRange().getBegin());
58 mlir::Location end = getLoc(s.getSourceRange().getEnd());
59 llvm::SmallVector<mlir::Type> retTy;
60 llvm::SmallVector<mlir::Value> operands;
61 auto op = builder.create<LoopOp>(start, retTy, operands);
62
63 // TODO(OpenACC): In the future we are going to need to come up with a
64 // transformation here that can teach the acc.loop how to figure out the
65 // 'lowerbound', 'upperbound', and 'step'.
66 //
67 // -'upperbound' should fortunately be pretty easy as it should be
68 // in the initialization section of the cir.for loop. In Sema, we limit to
69 // just the forms 'Var = init', `Type Var = init`, or `Var = init` (where it
70 // is an operator= call)`. However, as those are all necessary to emit for
71 // the init section of the for loop, they should be inside the initial
72 // cir.scope.
73 //
74 // -'upperbound' should be somewhat easy to determine. Sema is limiting this
75 // to: ==, <, >, !=, <=, >= builtin operators, the overloaded 'comparison'
76 // operations, and member-call expressions.
77 //
78 // For the builtin comparison operators, we can pretty well deduce based on
79 // the comparison what the 'end' object is going to be, and the inclusive
80 // nature of it.
81 //
82 // For the overloaded operators, Sema will ensure that at least one side of
83 // the operator is the init variable, so we can deduce the comparison there
84 // too. The standard places no real bounds on WHAT the comparison operators do
85 // for a `RandomAccessIterator` however, so we'll have to just 'assume' they
86 // do the right thing? Note that this might be incrementing by a different
87 // 'object', not an integral, so it isn't really clear to me what we can do to
88 // determine the other side.
89 //
90 // Member-call expressions are the difficult ones. I don't think there is
91 // anything we can deduce from this to determine the 'end', so we might end up
92 // having to go back to Sema and make this ill-formed.
93 //
94 // HOWEVER: What ACC dialect REALLY cares about is the tripcount, which you
95 // cannot get (in the case of `RandomAccessIterator`) from JUST 'upperbound'
96 // and 'lowerbound'. We will likely have to provide a 'recipe' equivalent to
97 // `std::distance` instead. In the case of integer/pointers, it is fairly
98 // simple to find: it is just the mathematical subtraction. Howver, in the
99 // case of `RandomAccessIterator`, we have to enable the use of `operator-`.
100 // FORTUNATELY the standard requires this to work correctly for
101 // `RandomAccessIterator`, so we don't have to implement a `std::distance`
102 // that loops through, like we would for a forward/etc iterator.
103 //
104 // 'step': Sema is currently allowing builtin ++,--, +=, -=, *=, /=, and =
105 // operators. Additionally, it allows the equivalent for the operator-call, as
106 // well as member-call.
107 //
108 // For builtin operators, we perhaps should refine the assignment here. It
109 // doesn't really help us know the 'step' count at all, but we could perhaps
110 // do one more step of analysis in Sema to allow something like Var = Var + 1.
111 // For the others, this should get us the step reasonably well.
112 //
113 // For the overloaded operators, we have the same problems as for
114 // 'upperbound', plus not really knowing what they do. Member-call expressions
115 // are again difficult, and we might want to reconsider allowing these in
116 // Sema.
117 //
118
119 // Emit all clauses.
120 emitOpenACCClauses(op, s.getDirectiveKind(), s.getDirectiveLoc(),
121 s.clauses());
122
123 updateLoopOpParallelism(op, s.isOrphanedLoopConstruct(),
124 s.getParentComputeConstructKind());
125
126 mlir::LogicalResult stmtRes = mlir::success();
127 // Emit body.
128 {
129 mlir::Block &block = op.getRegion().emplaceBlock();
130 mlir::OpBuilder::InsertionGuard guardCase(builder);
131 builder.setInsertionPointToEnd(&block);
132 LexicalScope ls{*this, start, builder.getInsertionBlock()};
133 ActiveOpenACCLoopRAII activeLoop{*this, &op};
134
135 stmtRes = emitStmt(s.getLoop(), /*useCurrentScope=*/true);
136 builder.create<mlir::acc::YieldOp>(end);
137 }
138
139 return stmtRes;
140 }
141