[MLIR][LLVMIR] Add support for empty global ctor/dtor lists #128969
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@llvm/pr-subscribers-mlir-llvm Author: Bruno Cardoso Lopes (bcardosolopes) ChangesFull diff: https://github.com/llvm/llvm-project/pull/128969.diff 5 Files Affected:
diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index 8445e609c2244..edaacb883f0c2 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -1071,32 +1071,39 @@ LogicalResult
ModuleImport::convertGlobalCtorsAndDtors(llvm::GlobalVariable *globalVar) {
if (!globalVar->hasInitializer() || !globalVar->hasAppendingLinkage())
return failure();
- auto *initializer =
- dyn_cast<llvm::ConstantArray>(globalVar->getInitializer());
- if (!initializer)
+ llvm::Constant *initializer = globalVar->getInitializer();
+
+ bool knownInit = isa<llvm::ConstantArray>(initializer) ||
+ isa<llvm::ConstantAggregateZero>(initializer);
+ if (!knownInit)
return failure();
SmallVector<Attribute> funcs;
SmallVector<int32_t> priorities;
- for (llvm::Value *operand : initializer->operands()) {
- auto *aggregate = dyn_cast<llvm::ConstantAggregate>(operand);
- if (!aggregate || aggregate->getNumOperands() != 3)
- return failure();
+ if (auto caInit = dyn_cast<llvm::ConstantArray>(initializer)) {
+ for (llvm::Value *operand : initializer->operands()) {
+ auto *aggregate = dyn_cast<llvm::ConstantAggregate>(operand);
+ if (!aggregate || aggregate->getNumOperands() != 3)
+ return failure();
- auto *priority = dyn_cast<llvm::ConstantInt>(aggregate->getOperand(0));
- auto *func = dyn_cast<llvm::Function>(aggregate->getOperand(1));
- auto *data = dyn_cast<llvm::Constant>(aggregate->getOperand(2));
- if (!priority || !func || !data)
- return failure();
+ auto *priority = dyn_cast<llvm::ConstantInt>(aggregate->getOperand(0));
+ auto *func = dyn_cast<llvm::Function>(aggregate->getOperand(1));
+ auto *data = dyn_cast<llvm::Constant>(aggregate->getOperand(2));
+ if (!priority || !func || !data)
+ return failure();
- // GlobalCtorsOps and GlobalDtorsOps do not support non-null data fields.
- if (!data->isNullValue())
- return failure();
+ // GlobalCtorsOps and GlobalDtorsOps do not support non-null data fields.
+ if (!data->isNullValue())
+ return failure();
- funcs.push_back(FlatSymbolRefAttr::get(context, func->getName()));
- priorities.push_back(priority->getValue().getZExtValue());
+ funcs.push_back(FlatSymbolRefAttr::get(context, func->getName()));
+ priorities.push_back(priority->getValue().getZExtValue());
+ }
}
+ // Note: no action needed for ConstantAggregateZero, which implies empty
+ // ctor/dtor lists.
+
// Insert the global after the last one or at the start of the module.
OpBuilder::InsertionGuard guard = setGlobalInsertionPoint();
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 5cd841ee2df91..c6bfb9566a4e1 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -1258,16 +1258,37 @@ LogicalResult ModuleTranslation::convertGlobalsAndAliases() {
auto dtorOp = dyn_cast<GlobalDtorsOp>(op);
if (!ctorOp && !dtorOp)
continue;
- auto range = ctorOp ? llvm::zip(ctorOp.getCtors(), ctorOp.getPriorities())
- : llvm::zip(dtorOp.getDtors(), dtorOp.getPriorities());
- auto appendGlobalFn =
- ctorOp ? llvm::appendToGlobalCtors : llvm::appendToGlobalDtors;
- for (auto symbolAndPriority : range) {
- llvm::Function *f = lookupFunction(
- cast<FlatSymbolRefAttr>(std::get<0>(symbolAndPriority)).getValue());
- appendGlobalFn(*llvmModule, f,
- cast<IntegerAttr>(std::get<1>(symbolAndPriority)).getInt(),
- /*Data=*/nullptr);
+
+ // The empty / zero initialized version of llvm.global_(c|d)tors cannot be
+ // handled by appendGlobalFn logic below, which just ignores empty (c|d)tor
+ // lists. Make sure it gets emitted.
+ if ((ctorOp && ctorOp.getCtors().empty()) ||
+ (dtorOp && dtorOp.getDtors().empty())) {
+ llvm::IRBuilder<llvm::TargetFolder> builder(
+ llvmModule->getContext(),
+ llvm::TargetFolder(llvmModule->getDataLayout()));
+ llvm::Type *eltTy = llvm::StructType::get(
+ builder.getInt32Ty(), builder.getPtrTy(), builder.getPtrTy());
+ llvm::ArrayType *at = llvm::ArrayType::get(eltTy, 0);
+ llvm::Constant *zeroInit = llvm::Constant::getNullValue(at);
+ (void)new llvm::GlobalVariable(
+ *llvmModule, zeroInit->getType(), false,
+ llvm::GlobalValue::AppendingLinkage, zeroInit,
+ ctorOp ? "llvm.global_ctors" : "llvm.global_dtors");
+ } else {
+ auto range = ctorOp
+ ? llvm::zip(ctorOp.getCtors(), ctorOp.getPriorities())
+ : llvm::zip(dtorOp.getDtors(), dtorOp.getPriorities());
+ auto appendGlobalFn =
+ ctorOp ? llvm::appendToGlobalCtors : llvm::appendToGlobalDtors;
+ for (auto symbolAndPriority : range) {
+ llvm::Function *f = lookupFunction(
+ cast<FlatSymbolRefAttr>(std::get<0>(symbolAndPriority)).getValue());
+ appendGlobalFn(
+ *llvmModule, f,
+ cast<IntegerAttr>(std::get<1>(symbolAndPriority)).getInt(),
+ /*Data=*/nullptr);
+ }
}
}
diff --git a/mlir/test/Dialect/LLVMIR/global.mlir b/mlir/test/Dialect/LLVMIR/global.mlir
index 79d1cafabfbed..bd3584de9a405 100644
--- a/mlir/test/Dialect/LLVMIR/global.mlir
+++ b/mlir/test/Dialect/LLVMIR/global.mlir
@@ -233,6 +233,14 @@ llvm.mlir.global_ctors { ctors = [@ctor], priorities = [0 : i32]}
// -----
+// CHECK: llvm.mlir.global_ctors {ctors = [], priorities = []}
+llvm.mlir.global_ctors {ctors = [], priorities = []}
+
+// CHECK: llvm.mlir.global_dtors {dtors = [], priorities = []}
+llvm.mlir.global_dtors {dtors = [], priorities = []}
+
+// -----
+
llvm.func @dtor() {
llvm.return
}
diff --git a/mlir/test/Target/LLVMIR/Import/global-variables.ll b/mlir/test/Target/LLVMIR/Import/global-variables.ll
index fbeda4cd42af8..b809c93d772f5 100644
--- a/mlir/test/Target/LLVMIR/Import/global-variables.ll
+++ b/mlir/test/Target/LLVMIR/Import/global-variables.ll
@@ -256,6 +256,14 @@ define void @bar() {
; // -----
+; CHECK: llvm.mlir.global_ctors {ctors = [], priorities = []}
+@llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+
+; CHECK: llvm.mlir.global_dtors {dtors = [], priorities = []}
+@llvm.global_dtors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+
+; // -----
+
; Visibility attribute.
; CHECK: llvm.mlir.global external hidden constant @hidden("string")
diff --git a/mlir/test/Target/LLVMIR/llvmir.mlir b/mlir/test/Target/LLVMIR/llvmir.mlir
index 7f9a3ba79d724..db2e08742dbca 100644
--- a/mlir/test/Target/LLVMIR/llvmir.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir.mlir
@@ -1859,6 +1859,14 @@ llvm.func @foo() {
// -----
+// CHECK: @llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+llvm.mlir.global_ctors {ctors = [], priorities = []}
+
+// CHECK: @llvm.global_dtors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+llvm.mlir.global_dtors {dtors = [], priorities = []}
+
+// -----
+
// CHECK: @llvm.global_dtors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 0, ptr @foo, ptr null }]
llvm.mlir.global_dtors { dtors = [@foo], priorities = [0 : i32]}
|
|
@llvm/pr-subscribers-mlir Author: Bruno Cardoso Lopes (bcardosolopes) ChangesFull diff: https://github.com/llvm/llvm-project/pull/128969.diff 5 Files Affected:
diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index 8445e609c2244..edaacb883f0c2 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -1071,32 +1071,39 @@ LogicalResult
ModuleImport::convertGlobalCtorsAndDtors(llvm::GlobalVariable *globalVar) {
if (!globalVar->hasInitializer() || !globalVar->hasAppendingLinkage())
return failure();
- auto *initializer =
- dyn_cast<llvm::ConstantArray>(globalVar->getInitializer());
- if (!initializer)
+ llvm::Constant *initializer = globalVar->getInitializer();
+
+ bool knownInit = isa<llvm::ConstantArray>(initializer) ||
+ isa<llvm::ConstantAggregateZero>(initializer);
+ if (!knownInit)
return failure();
SmallVector<Attribute> funcs;
SmallVector<int32_t> priorities;
- for (llvm::Value *operand : initializer->operands()) {
- auto *aggregate = dyn_cast<llvm::ConstantAggregate>(operand);
- if (!aggregate || aggregate->getNumOperands() != 3)
- return failure();
+ if (auto caInit = dyn_cast<llvm::ConstantArray>(initializer)) {
+ for (llvm::Value *operand : initializer->operands()) {
+ auto *aggregate = dyn_cast<llvm::ConstantAggregate>(operand);
+ if (!aggregate || aggregate->getNumOperands() != 3)
+ return failure();
- auto *priority = dyn_cast<llvm::ConstantInt>(aggregate->getOperand(0));
- auto *func = dyn_cast<llvm::Function>(aggregate->getOperand(1));
- auto *data = dyn_cast<llvm::Constant>(aggregate->getOperand(2));
- if (!priority || !func || !data)
- return failure();
+ auto *priority = dyn_cast<llvm::ConstantInt>(aggregate->getOperand(0));
+ auto *func = dyn_cast<llvm::Function>(aggregate->getOperand(1));
+ auto *data = dyn_cast<llvm::Constant>(aggregate->getOperand(2));
+ if (!priority || !func || !data)
+ return failure();
- // GlobalCtorsOps and GlobalDtorsOps do not support non-null data fields.
- if (!data->isNullValue())
- return failure();
+ // GlobalCtorsOps and GlobalDtorsOps do not support non-null data fields.
+ if (!data->isNullValue())
+ return failure();
- funcs.push_back(FlatSymbolRefAttr::get(context, func->getName()));
- priorities.push_back(priority->getValue().getZExtValue());
+ funcs.push_back(FlatSymbolRefAttr::get(context, func->getName()));
+ priorities.push_back(priority->getValue().getZExtValue());
+ }
}
+ // Note: no action needed for ConstantAggregateZero, which implies empty
+ // ctor/dtor lists.
+
// Insert the global after the last one or at the start of the module.
OpBuilder::InsertionGuard guard = setGlobalInsertionPoint();
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 5cd841ee2df91..c6bfb9566a4e1 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -1258,16 +1258,37 @@ LogicalResult ModuleTranslation::convertGlobalsAndAliases() {
auto dtorOp = dyn_cast<GlobalDtorsOp>(op);
if (!ctorOp && !dtorOp)
continue;
- auto range = ctorOp ? llvm::zip(ctorOp.getCtors(), ctorOp.getPriorities())
- : llvm::zip(dtorOp.getDtors(), dtorOp.getPriorities());
- auto appendGlobalFn =
- ctorOp ? llvm::appendToGlobalCtors : llvm::appendToGlobalDtors;
- for (auto symbolAndPriority : range) {
- llvm::Function *f = lookupFunction(
- cast<FlatSymbolRefAttr>(std::get<0>(symbolAndPriority)).getValue());
- appendGlobalFn(*llvmModule, f,
- cast<IntegerAttr>(std::get<1>(symbolAndPriority)).getInt(),
- /*Data=*/nullptr);
+
+ // The empty / zero initialized version of llvm.global_(c|d)tors cannot be
+ // handled by appendGlobalFn logic below, which just ignores empty (c|d)tor
+ // lists. Make sure it gets emitted.
+ if ((ctorOp && ctorOp.getCtors().empty()) ||
+ (dtorOp && dtorOp.getDtors().empty())) {
+ llvm::IRBuilder<llvm::TargetFolder> builder(
+ llvmModule->getContext(),
+ llvm::TargetFolder(llvmModule->getDataLayout()));
+ llvm::Type *eltTy = llvm::StructType::get(
+ builder.getInt32Ty(), builder.getPtrTy(), builder.getPtrTy());
+ llvm::ArrayType *at = llvm::ArrayType::get(eltTy, 0);
+ llvm::Constant *zeroInit = llvm::Constant::getNullValue(at);
+ (void)new llvm::GlobalVariable(
+ *llvmModule, zeroInit->getType(), false,
+ llvm::GlobalValue::AppendingLinkage, zeroInit,
+ ctorOp ? "llvm.global_ctors" : "llvm.global_dtors");
+ } else {
+ auto range = ctorOp
+ ? llvm::zip(ctorOp.getCtors(), ctorOp.getPriorities())
+ : llvm::zip(dtorOp.getDtors(), dtorOp.getPriorities());
+ auto appendGlobalFn =
+ ctorOp ? llvm::appendToGlobalCtors : llvm::appendToGlobalDtors;
+ for (auto symbolAndPriority : range) {
+ llvm::Function *f = lookupFunction(
+ cast<FlatSymbolRefAttr>(std::get<0>(symbolAndPriority)).getValue());
+ appendGlobalFn(
+ *llvmModule, f,
+ cast<IntegerAttr>(std::get<1>(symbolAndPriority)).getInt(),
+ /*Data=*/nullptr);
+ }
}
}
diff --git a/mlir/test/Dialect/LLVMIR/global.mlir b/mlir/test/Dialect/LLVMIR/global.mlir
index 79d1cafabfbed..bd3584de9a405 100644
--- a/mlir/test/Dialect/LLVMIR/global.mlir
+++ b/mlir/test/Dialect/LLVMIR/global.mlir
@@ -233,6 +233,14 @@ llvm.mlir.global_ctors { ctors = [@ctor], priorities = [0 : i32]}
// -----
+// CHECK: llvm.mlir.global_ctors {ctors = [], priorities = []}
+llvm.mlir.global_ctors {ctors = [], priorities = []}
+
+// CHECK: llvm.mlir.global_dtors {dtors = [], priorities = []}
+llvm.mlir.global_dtors {dtors = [], priorities = []}
+
+// -----
+
llvm.func @dtor() {
llvm.return
}
diff --git a/mlir/test/Target/LLVMIR/Import/global-variables.ll b/mlir/test/Target/LLVMIR/Import/global-variables.ll
index fbeda4cd42af8..b809c93d772f5 100644
--- a/mlir/test/Target/LLVMIR/Import/global-variables.ll
+++ b/mlir/test/Target/LLVMIR/Import/global-variables.ll
@@ -256,6 +256,14 @@ define void @bar() {
; // -----
+; CHECK: llvm.mlir.global_ctors {ctors = [], priorities = []}
+@llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+
+; CHECK: llvm.mlir.global_dtors {dtors = [], priorities = []}
+@llvm.global_dtors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+
+; // -----
+
; Visibility attribute.
; CHECK: llvm.mlir.global external hidden constant @hidden("string")
diff --git a/mlir/test/Target/LLVMIR/llvmir.mlir b/mlir/test/Target/LLVMIR/llvmir.mlir
index 7f9a3ba79d724..db2e08742dbca 100644
--- a/mlir/test/Target/LLVMIR/llvmir.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir.mlir
@@ -1859,6 +1859,14 @@ llvm.func @foo() {
// -----
+// CHECK: @llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+llvm.mlir.global_ctors {ctors = [], priorities = []}
+
+// CHECK: @llvm.global_dtors = appending global [0 x { i32, ptr, ptr }] zeroinitializer
+llvm.mlir.global_dtors {dtors = [], priorities = []}
+
+// -----
+
// CHECK: @llvm.global_dtors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 0, ptr @foo, ptr null }]
llvm.mlir.global_dtors { dtors = [@foo], priorities = [0 : i32]}
|
|
Can you expand on why we should not just drop empty decls? |
Dinistro
reviewed
Feb 27, 2025
LLVM IR emitted in our C++ codebase contains If you think this should be represented differently (i.e. not by empty lists), please let me know what approach you'd like to see. |
FWIW, |
gysit
approved these changes
Feb 27, 2025
|
@Dinistro let me know your thoughts! |
Dinistro
approved these changes
Feb 28, 2025
cheezeburglar
pushed a commit
to cheezeburglar/llvm-project
that referenced
this pull request
Feb 28, 2025
) LLVM IR emitted in from C++ may contain `@llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer`. Before this PR, if we try to roundtrip code like this from the importer, we'll end up with nothing in place. Note that `llvm::appendToGlobalCtors` ignores empty lists and this PR uses the same approach as `llvm-as`, which doesn't use the utilities from `llvm/lib/Transforms/Utils/ModuleUtils.cpp` in order to build this - it calls into creating a global variable from scratch.
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LLVM IR emitted in from C++ may contain
@llvm.global_ctors = appending global [0 x { i32, ptr, ptr }] zeroinitializer. Before this PR, if we try to roundtrip code like this from the importer, we'll end up with nothing in place.Note that
llvm::appendToGlobalCtorsignores empty lists and this PR uses the same approach asllvm-as, which doesn't use the utilities fromllvm/lib/Transforms/Utils/ModuleUtils.cppin order to build this - it calls into creating a global variable from scratch.