[Mlir-commits] [mlir] e119980 - [mlir] LLVM dialect: move ensureDistinctSuccessors out of std->LLVM conversion
Alex Zinenko
llvmlistbot at llvm.org
Tue Mar 17 07:22:21 PDT 2020
Author: Alex Zinenko
Date: 2020-03-17T15:22:14+01:00
New Revision: e119980f3f84cf83a81bb6dec9ebadb2b770a500
URL: https://github.com/llvm/llvm-project/commit/e119980f3f84cf83a81bb6dec9ebadb2b770a500
DIFF: https://github.com/llvm/llvm-project/commit/e119980f3f84cf83a81bb6dec9ebadb2b770a500.diff
LOG: [mlir] LLVM dialect: move ensureDistinctSuccessors out of std->LLVM conversion
MLIR supports terminators that have the same successor block with different
block operands, which cannot be expressed in the LLVM's phi-notation as the
block identifier is used to tell apart the predecessors. This limitation can be
worked around by branching to a new block instead, with this new block
unconditionally branching to the original successor and forwarding the
argument. Until now, this transformation was performed during the conversion
from the Standard to the LLVM dialect. This does not scale well to multiple
dialects targeting the LLVM dialect as all of them would have to be aware of
this limitation and perform the preparatory transformation. Instead, do it as a
separate pass and run it immediately before the translation.
Differential Revision: https://reviews.llvm.org/D75619
Added:
mlir/include/mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h
mlir/lib/Dialect/LLVMIR/Transforms/CMakeLists.txt
mlir/lib/Dialect/LLVMIR/Transforms/LegalizeForExport.cpp
mlir/test/Dialect/LLVMIR/legalize-for-export.mlir
Modified:
mlir/include/mlir/Conversion/StandardToLLVM/ConvertStandardToLLVMPass.h
mlir/include/mlir/InitAllPasses.h
mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
mlir/lib/Dialect/LLVMIR/CMakeLists.txt
mlir/lib/Target/CMakeLists.txt
mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
Removed:
################################################################################
diff --git a/mlir/include/mlir/Conversion/StandardToLLVM/ConvertStandardToLLVMPass.h b/mlir/include/mlir/Conversion/StandardToLLVM/ConvertStandardToLLVMPass.h
index 7d2a076aeb25..dd815b381cc9 100644
--- a/mlir/include/mlir/Conversion/StandardToLLVM/ConvertStandardToLLVMPass.h
+++ b/mlir/include/mlir/Conversion/StandardToLLVM/ConvertStandardToLLVMPass.h
@@ -61,15 +61,6 @@ std::unique_ptr<OpPassBase<ModuleOp>>
createLowerToLLVMPass(bool useAlloca = false, bool useBarePtrCallConv = false,
bool emitCWrappers = false);
-namespace LLVM {
-/// Make argument-taking successors of each block distinct. PHI nodes in LLVM
-/// IR use the predecessor ID to identify which value to take. They do not
-/// support
diff erent values coming from the same predecessor. If a block has
-/// another block as a successor more than once with
diff erent values, insert
-/// a new dummy block for LLVM PHI nodes to tell the sources apart.
-void ensureDistinctSuccessors(ModuleOp m);
-} // namespace LLVM
-
} // namespace mlir
#endif // MLIR_CONVERSION_STANDARDTOLLVM_CONVERTSTANDARDTOLLVMPASS_H_
diff --git a/mlir/include/mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h b/mlir/include/mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h
new file mode 100644
index 000000000000..7d6ec0165d4a
--- /dev/null
+++ b/mlir/include/mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h
@@ -0,0 +1,34 @@
+//===- LegalizeForExport.h - Prepare for translation to LLVM IR -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_DIALECT_LLVMIR_TRANSFORMS_LEGALIZE_FOR_EXPORT_H
+#define MLIR_DIALECT_LLVMIR_TRANSFORMS_LEGALIZE_FOR_EXPORT_H
+
+#include <memory>
+
+namespace mlir {
+class Operation;
+class Pass;
+
+namespace LLVM {
+
+/// Make argument-taking successors of each block distinct. PHI nodes in LLVM
+/// IR use the predecessor ID to identify which value to take. They do not
+/// support
diff erent values coming from the same predecessor. If a block has
+/// another block as a successor more than once with
diff erent values, insert
+/// a new dummy block for LLVM PHI nodes to tell the sources apart.
+void ensureDistinctSuccessors(Operation *op);
+
+/// Creates a pass that legalizes the LLVM dialect operations so that they can
+/// be translated to LLVM IR.
+std::unique_ptr<Pass> createLegalizeForExportPass();
+
+} // namespace LLVM
+} // namespace mlir
+
+#endif // MLIR_DIALECT_LLVMIR_TRANSFORMS_LEGALIZE_FOR_EXPORT_H
diff --git a/mlir/include/mlir/InitAllPasses.h b/mlir/include/mlir/InitAllPasses.h
index 009cc7309cff..9db334a76b64 100644
--- a/mlir/include/mlir/InitAllPasses.h
+++ b/mlir/include/mlir/InitAllPasses.h
@@ -26,6 +26,7 @@
#include "mlir/Conversion/StandardToSPIRV/ConvertStandardToSPIRVPass.h"
#include "mlir/Dialect/FxpMathOps/Passes.h"
#include "mlir/Dialect/GPU/Passes.h"
+#include "mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h"
#include "mlir/Dialect/Linalg/Passes.h"
#include "mlir/Dialect/LoopOps/Passes.h"
#include "mlir/Dialect/QuantOps/Passes.h"
@@ -107,6 +108,9 @@ inline void registerAllPasses() {
createConvertLinalgToAffineLoopsPass();
createConvertLinalgToLLVMPass();
+ // LLVM
+ LLVM::createLegalizeForExportPass();
+
// LoopOps
createParallelLoopFusionPass();
createParallelLoopSpecializationPass();
diff --git a/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h b/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
index d7cd0d2186ae..f6b299dbd1ae 100644
--- a/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
+++ b/mlir/include/mlir/Target/LLVMIR/ModuleTranslation.h
@@ -15,6 +15,7 @@
#define MLIR_TARGET_LLVMIR_MODULETRANSLATION_H
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h"
#include "mlir/IR/Block.h"
#include "mlir/IR/Module.h"
#include "mlir/IR/Value.h"
@@ -57,6 +58,8 @@ class ModuleTranslation {
if (!llvmModule)
return nullptr;
+ LLVM::ensureDistinctSuccessors(m);
+
T translator(m, std::move(llvmModule));
if (failed(translator.convertGlobals()))
return nullptr;
diff --git a/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp b/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
index c7c479bf6779..3e99eb598dfc 100644
--- a/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
+++ b/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
@@ -2785,49 +2785,6 @@ struct AtomicCmpXchgOpLowering : public LoadStoreOpLowering<AtomicRMWOp> {
} // namespace
-static void ensureDistinctSuccessors(Block &bb) {
- Operation *terminator = bb.getTerminator();
- if (terminator->getNumSuccessors() < 2)
- return;
-
- // Find repeated successors with arguments.
- llvm::SmallDenseMap<Block *, SmallVector<int, 4>> successorPositions;
- for (int i = 0, e = terminator->getNumSuccessors(); i < e; ++i) {
- Block *successor = terminator->getSuccessor(i);
- // Blocks with no arguments are safe even if they appear multiple times
- // because they don't need PHI nodes.
- if (successor->getNumArguments() == 0)
- continue;
- successorPositions[successor].push_back(i);
- }
-
- // If a successor appears for the second or more time in the terminator,
- // create a new dummy block that unconditionally branches to the original
- // destination, and retarget the terminator to branch to this new block.
- // There is no need to pass arguments to the dummy block because it will be
- // dominated by the original block and can therefore use any values defined in
- // the original block.
- OpBuilder builder(terminator->getContext());
- for (const auto &successor : successorPositions) {
- // Start from the second occurrence of a block in the successor list.
- for (int position : llvm::drop_begin(successor.second, 1)) {
- Block *dummyBlock = builder.createBlock(bb.getParent());
- terminator->setSuccessor(dummyBlock, position);
- dummyBlock->addArguments(successor.first->getArgumentTypes());
- builder.create<BranchOp>(terminator->getLoc(), successor.first,
- dummyBlock->getArguments());
- }
- }
-}
-
-void mlir::LLVM::ensureDistinctSuccessors(ModuleOp m) {
- for (auto f : m.getOps<FuncOp>()) {
- for (auto &bb : f.getBlocks()) {
- ::ensureDistinctSuccessors(bb);
- }
- }
-}
-
/// Collect a set of patterns to convert from the Standard dialect to LLVM.
void mlir::populateStdToLLVMNonMemoryConversionPatterns(
LLVMTypeConverter &converter, OwningRewritePatternList &patterns) {
@@ -3024,7 +2981,6 @@ struct LLVMLoweringPass : public ModulePass<LLVMLoweringPass> {
}
ModuleOp m = getModule();
- LLVM::ensureDistinctSuccessors(m);
LLVMTypeConverterCustomization customs;
customs.funcArgConverter = useBarePtrCallConv ? barePtrFuncArgTypeConverter
diff --git a/mlir/lib/Dialect/LLVMIR/CMakeLists.txt b/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
index fb94a220835c..2e53d29f768d 100644
--- a/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
+++ b/mlir/lib/Dialect/LLVMIR/CMakeLists.txt
@@ -1,3 +1,5 @@
+add_subdirectory(Transforms)
+
add_mlir_dialect_library(MLIRLLVMIR
IR/LLVMDialect.cpp
diff --git a/mlir/lib/Dialect/LLVMIR/Transforms/CMakeLists.txt b/mlir/lib/Dialect/LLVMIR/Transforms/CMakeLists.txt
new file mode 100644
index 000000000000..6b37b060de6c
--- /dev/null
+++ b/mlir/lib/Dialect/LLVMIR/Transforms/CMakeLists.txt
@@ -0,0 +1,10 @@
+add_mlir_dialect_library(MLIRLLVMIRTransforms
+ LegalizeForExport.cpp
+ )
+
+target_link_libraries(MLIRLLVMIRTransforms
+ PUBLIC
+ MLIRIR
+ MLIRLLVMIR
+ MLIRPass
+ )
diff --git a/mlir/lib/Dialect/LLVMIR/Transforms/LegalizeForExport.cpp b/mlir/lib/Dialect/LLVMIR/Transforms/LegalizeForExport.cpp
new file mode 100644
index 000000000000..fce4045f1aa3
--- /dev/null
+++ b/mlir/lib/Dialect/LLVMIR/Transforms/LegalizeForExport.cpp
@@ -0,0 +1,73 @@
+//===- LegalizeForExport.cpp - Prepare for translation to LLVM IR ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/IR/Block.h"
+#include "mlir/IR/Builders.h"
+#include "mlir/IR/Module.h"
+#include "mlir/Pass/Pass.h"
+
+using namespace mlir;
+
+static void ensureDistinctSuccessors(Block &bb) {
+ auto *terminator = bb.getTerminator();
+
+ // Find repeated successors with arguments.
+ llvm::SmallDenseMap<Block *, SmallVector<int, 4>> successorPositions;
+ for (int i = 0, e = terminator->getNumSuccessors(); i < e; ++i) {
+ Block *successor = terminator->getSuccessor(i);
+ // Blocks with no arguments are safe even if they appear multiple times
+ // because they don't need PHI nodes.
+ if (successor->getNumArguments() == 0)
+ continue;
+ successorPositions[successor].push_back(i);
+ }
+
+ // If a successor appears for the second or more time in the terminator,
+ // create a new dummy block that unconditionally branches to the original
+ // destination, and retarget the terminator to branch to this new block.
+ // There is no need to pass arguments to the dummy block because it will be
+ // dominated by the original block and can therefore use any values defined in
+ // the original block.
+ OpBuilder builder(terminator->getContext());
+ for (const auto &successor : successorPositions) {
+ // Start from the second occurrence of a block in the successor list.
+ for (int position : llvm::drop_begin(successor.second, 1)) {
+ Block *dummyBlock = builder.createBlock(bb.getParent());
+ terminator->setSuccessor(dummyBlock, position);
+ dummyBlock->addArguments(successor.first->getArgumentTypes());
+ builder.create<LLVM::BrOp>(terminator->getLoc(),
+ dummyBlock->getArguments(), successor.first);
+ }
+ }
+}
+
+void mlir::LLVM::ensureDistinctSuccessors(Operation *op) {
+ op->walk([](LLVMFuncOp f) {
+ for (auto &bb : f.getBlocks()) {
+ ::ensureDistinctSuccessors(bb);
+ }
+ });
+}
+
+namespace {
+struct LegalizeForExportPass : public OperationPass<LegalizeForExportPass> {
+ void runOnOperation() override {
+ LLVM::ensureDistinctSuccessors(getOperation());
+ }
+};
+} // end namespace
+
+std::unique_ptr<Pass> LLVM::createLegalizeForExportPass() {
+ return std::make_unique<LegalizeForExportPass>();
+}
+
+static PassRegistration<LegalizeForExportPass>
+ pass("llvm-legalize-for-export",
+ "Legalize LLVM dialect to be convertible to LLVM IR");
diff --git a/mlir/lib/Target/CMakeLists.txt b/mlir/lib/Target/CMakeLists.txt
index f51b46b4da1a..b68bfa8d3cf2 100644
--- a/mlir/lib/Target/CMakeLists.txt
+++ b/mlir/lib/Target/CMakeLists.txt
@@ -10,6 +10,7 @@ add_mlir_library(MLIRTargetLLVMIRModuleTranslation
target_link_libraries(MLIRTargetLLVMIRModuleTranslation
PUBLIC
MLIRLLVMIR
+ MLIRLLVMIRTransforms
LLVMCore
LLVMIRReader
LLVMSupport
diff --git a/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir b/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
index 6406a547bef5..699ea31836a5 100644
--- a/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
+++ b/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
@@ -554,19 +554,6 @@ func @dfs_block_order(%arg0: i32) -> (i32) {
// CHECK-NEXT: llvm.br ^bb1
br ^bb1
}
-// CHECK-LABEL: func @cond_br_same_target(%arg0: !llvm.i1, %arg1: !llvm.i32, %arg2: !llvm.i32)
-func @cond_br_same_target(%arg0: i1, %arg1: i32, %arg2 : i32) -> (i32) {
-// CHECK-NEXT: llvm.cond_br %arg0, ^[[origBlock:bb[0-9]+]](%arg1 : !llvm.i32), ^[[dummyBlock:bb[0-9]+]](%arg2 : !llvm.i32)
- cond_br %arg0, ^bb1(%arg1 : i32), ^bb1(%arg2 : i32)
-
-// CHECK: ^[[origBlock]](%[[BLOCKARG1:.*]]: !llvm.i32):
-// CHECK-NEXT: llvm.return %[[BLOCKARG1]] : !llvm.i32
-^bb1(%0 : i32):
- return %0 : i32
-
-// CHECK: ^[[dummyBlock]](%[[BLOCKARG2:.*]]: !llvm.i32):
-// CHECK-NEXT: llvm.br ^[[origBlock]](%[[BLOCKARG2]] : !llvm.i32)
-}
// CHECK-LABEL: func @fcmp(%arg0: !llvm.float, %arg1: !llvm.float) {
func @fcmp(f32, f32) -> () {
diff --git a/mlir/test/Dialect/LLVMIR/legalize-for-export.mlir b/mlir/test/Dialect/LLVMIR/legalize-for-export.mlir
new file mode 100644
index 000000000000..f695f2c362f8
--- /dev/null
+++ b/mlir/test/Dialect/LLVMIR/legalize-for-export.mlir
@@ -0,0 +1,31 @@
+// RUN: mlir-opt -llvm-legalize-for-export %s | FileCheck %s
+
+// Verifies that duplicate successor with
diff erent arguments are deduplicated
+// by introducing a new block that forwards its arguments to the original
+// successor through an unconditional branch.
+// CHECK-LABEL: @repeated_successor_
diff erent_args
+llvm.func @repeated_successor_
diff erent_args(%arg0: !llvm.i1, %arg1: !llvm.i32, %arg2: !llvm.i32) {
+ // CHECK: llvm.cond_br %{{.*}}, ^[[BB1:.*]]({{.*}}), ^[[BB2:.*]]({{.*}})
+ llvm.cond_br %arg0, ^bb1(%arg1: !llvm.i32), ^bb1(%arg2: !llvm.i32)
+
+// CHECK: ^[[BB1]]({{.*}}):
+^bb1(%arg3: !llvm.i32):
+ llvm.return
+
+// CHECK: ^[[BB2]](%[[ARG:.*]]: !llvm.i32):
+// CHECK: llvm.br ^[[BB1]](%[[ARG]] : !llvm.i32)
+}
+
+// Verifies that duplicate successors without arguments do not lead to the
+// introduction of new blocks during legalization.
+// CHECK-LABEL: @repeated_successor_no_args
+llvm.func @repeated_successor_no_args(%arg0: !llvm.i1) {
+ // CHECK: llvm.cond_br
+ llvm.cond_br %arg0, ^bb1, ^bb1
+
+// CHECK: ^{{.*}}:
+^bb1:
+ llvm.return
+
+// CHECK-NOT: ^{{.*}}:
+}
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