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//===- ControlFlowToSCF.h - ControlFlow to SCF -------------*- C++ ------*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Define conversions from the ControlFlow dialect to the SCF dialect.
//
//===----------------------------------------------------------------------===//
#include "mlir/Conversion/ControlFlowToSCF/ControlFlowToSCF.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
#include "mlir/Dialect/UB/IR/UBOps.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/CFGToSCF.h"
namespace mlir {
#define GEN_PASS_DEF_LIFTCONTROLFLOWTOSCFPASS
#include "mlir/Conversion/Passes.h.inc"
} // namespace mlir
using namespace mlir;
FailureOr<Operation *>
ControlFlowToSCFTransformation::createStructuredBranchRegionOp(
OpBuilder &builder, Operation *controlFlowCondOp, TypeRange resultTypes,
MutableArrayRef<Region> regions) {
if (auto condBrOp = dyn_cast<cf::CondBranchOp>(controlFlowCondOp)) {
assert(regions.size() == 2);
auto ifOp = scf::IfOp::create(builder, controlFlowCondOp->getLoc(),
resultTypes, condBrOp.getCondition());
ifOp.getThenRegion().takeBody(regions[0]);
ifOp.getElseRegion().takeBody(regions[1]);
return ifOp.getOperation();
}
if (auto switchOp = dyn_cast<cf::SwitchOp>(controlFlowCondOp)) {
// `getCFGSwitchValue` returns an i32 that we need to convert to index
// fist.
auto cast = arith::IndexCastUIOp::create(
builder, controlFlowCondOp->getLoc(), builder.getIndexType(),
switchOp.getFlag());
SmallVector<int64_t> cases;
if (auto caseValues = switchOp.getCaseValues())
llvm::append_range(
cases, llvm::map_range(*caseValues, [](const llvm::APInt &apInt) {
return apInt.getZExtValue();
}));
assert(regions.size() == cases.size() + 1);
auto indexSwitchOp =
scf::IndexSwitchOp::create(builder, controlFlowCondOp->getLoc(),
resultTypes, cast, cases, cases.size());
indexSwitchOp.getDefaultRegion().takeBody(regions[0]);
for (auto &&[targetRegion, sourceRegion] :
llvm::zip(indexSwitchOp.getCaseRegions(), llvm::drop_begin(regions)))
targetRegion.takeBody(sourceRegion);
return indexSwitchOp.getOperation();
}
controlFlowCondOp->emitOpError(
"Cannot convert unknown control flow op to structured control flow");
return failure();
}
LogicalResult
ControlFlowToSCFTransformation::createStructuredBranchRegionTerminatorOp(
Location loc, OpBuilder &builder, Operation *branchRegionOp,
Operation *replacedControlFlowOp, ValueRange results) {
scf::YieldOp::create(builder, loc, results);
return success();
}
FailureOr<Operation *>
ControlFlowToSCFTransformation::createStructuredDoWhileLoopOp(
OpBuilder &builder, Operation *replacedOp, ValueRange loopVariablesInit,
Value condition, ValueRange loopVariablesNextIter, Region &&loopBody) {
Location loc = replacedOp->getLoc();
auto whileOp = scf::WhileOp::create(
builder, loc, loopVariablesInit.getTypes(), loopVariablesInit);
whileOp.getBefore().takeBody(loopBody);
builder.setInsertionPointToEnd(&whileOp.getBefore().back());
// `getCFGSwitchValue` returns a i32. We therefore need to truncate the
// condition to i1 first. It is guaranteed to be either 0 or 1 already.
scf::ConditionOp::create(
builder, loc,
arith::TruncIOp::create(builder, loc, builder.getI1Type(), condition),
loopVariablesNextIter);
Block *afterBlock = builder.createBlock(&whileOp.getAfter());
afterBlock->addArguments(
loopVariablesInit.getTypes(),
SmallVector<Location>(loopVariablesInit.size(), loc));
scf::YieldOp::create(builder, loc, afterBlock->getArguments());
return whileOp.getOperation();
}
Value ControlFlowToSCFTransformation::getCFGSwitchValue(Location loc,
OpBuilder &builder,
unsigned int value) {
return arith::ConstantOp::create(builder, loc,
builder.getI32IntegerAttr(value));
}
void ControlFlowToSCFTransformation::createCFGSwitchOp(
Location loc, OpBuilder &builder, Value flag,
ArrayRef<unsigned int> caseValues, BlockRange caseDestinations,
ArrayRef<ValueRange> caseArguments, Block *defaultDest,
ValueRange defaultArgs) {
cf::SwitchOp::create(builder, loc, flag, defaultDest, defaultArgs,
llvm::to_vector_of<int32_t>(caseValues),
caseDestinations, caseArguments);
}
Value ControlFlowToSCFTransformation::getUndefValue(Location loc,
OpBuilder &builder,
Type type) {
return ub::PoisonOp::create(builder, loc, type, nullptr);
}
FailureOr<Operation *>
ControlFlowToSCFTransformation::createUnreachableTerminator(Location loc,
OpBuilder &builder,
Region ®ion) {
// TODO: This should create a `ub.unreachable` op. Once such an operation
// exists to make the pass independent of the func dialect. For now just
// return poison values.
Operation *parentOp = region.getParentOp();
auto funcOp = dyn_cast<func::FuncOp>(parentOp);
if (!funcOp)
return emitError(loc, "Cannot create unreachable terminator for '")
<< parentOp->getName() << "'";
return func::ReturnOp::create(
builder, loc,
llvm::map_to_vector(
funcOp.getResultTypes(),
[&](Type type) { return getUndefValue(loc, builder, type); }))
.getOperation();
}
namespace {
struct LiftControlFlowToSCF
: public impl::LiftControlFlowToSCFPassBase<LiftControlFlowToSCF> {
using Base::Base;
void runOnOperation() override {
ControlFlowToSCFTransformation transformation;
bool changed = false;
Operation *op = getOperation();
WalkResult result = op->walk([&](func::FuncOp funcOp) {
if (funcOp.getBody().empty())
return WalkResult::advance();
auto &domInfo = funcOp != op ? getChildAnalysis<DominanceInfo>(funcOp)
: getAnalysis<DominanceInfo>();
auto visitor = [&](Operation *innerOp) -> WalkResult {
for (Region ® : innerOp->getRegions()) {
FailureOr<bool> changedFunc =
transformCFGToSCF(reg, transformation, domInfo);
if (failed(changedFunc))
return WalkResult::interrupt();
changed |= *changedFunc;
}
return WalkResult::advance();
};
if (funcOp->walk<WalkOrder::PostOrder>(visitor).wasInterrupted())
return WalkResult::interrupt();
return WalkResult::advance();
});
if (result.wasInterrupted())
return signalPassFailure();
if (!changed)
markAllAnalysesPreserved();
}
};
} // namespace
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