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[CIR][Lowering] Deprecate attributes for LLVM zero-initialization #221

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Aug 21, 2023
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[CIR][Lowering] Deprecate attributes for LLVM zero-initialization #221

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b3f11b1
[CIR][Lowering] Deprecate attributes for LLVM zero-initialization
sitio-couto Aug 7, 2023
8351924
Update on "[CIR][Lowering] Deprecate attributes for LLVM zero-initial…
sitio-couto Aug 7, 2023
dd88a7c
Update on "[CIR][Lowering] Deprecate attributes for LLVM zero-initial…
sitio-couto Aug 21, 2023
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14 changes: 6 additions & 8 deletions clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1267,14 +1267,12 @@ class CIRGlobalOpLowering
return mlir::success();
} else if (isa<mlir::cir::ZeroAttr, mlir::cir::NullAttr>(init.value())) {
// TODO(cir): once LLVM's dialect has a proper zeroinitializer attribute
// this should be updated. For now, we tag the LLVM global with a cir.zero
// attribute that is later replaced with a zeroinitializer. Null pointers
// also use this path for simplicity, as we would otherwise require a
// region-based initialization for the global op.
auto llvmGlobalOp = rewriter.replaceOpWithNewOp<mlir::LLVM::GlobalOp>(
op, llvmType, isConst, linkage, symbol, nullptr);
auto cirZeroAttr = mlir::cir::ZeroAttr::get(getContext(), llvmType);
llvmGlobalOp->setAttr("cir.initial_value", cirZeroAttr);
// this should be updated. For now, we use a custom op to initialize
// globals to zero.
setupRegionInitializedLLVMGlobalOp(op, rewriter);
auto value =
lowerCirAttrAsValue(init.value(), loc, rewriter, typeConverter);
rewriter.create<mlir::LLVM::ReturnOp>(loc, value);
return mlir::success();
} else if (const auto structAttr =
init.value().dyn_cast<mlir::cir::ConstStructAttr>()) {
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11 changes: 0 additions & 11 deletions clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVMIR.cpp
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Expand Up @@ -40,17 +40,6 @@ class CIRDialectLLVMIRTranslationInterface
amendOperation(mlir::Operation *op, mlir::NamedAttribute attribute,
mlir::LLVM::ModuleTranslation &moduleTranslation) const final {

// Translate CIR's zero attribute to LLVM's zero initializer.
if (isa<mlir::cir::ZeroAttr>(attribute.getValue())) {
if (llvm::isa<mlir::LLVM::GlobalOp>(op)) {
auto *globalVal = llvm::cast<llvm::GlobalVariable>(
moduleTranslation.lookupGlobal(op));
globalVal->setInitializer(
llvm::Constant::getNullValue(globalVal->getValueType()));
} else
return op->emitError("#cir.zero not supported");
}

// Translate CIR's extra function attributes to LLVM's function attributes.
auto func = dyn_cast<mlir::LLVM::LLVMFuncOp>(op);
if (!func)
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11 changes: 11 additions & 0 deletions clang/test/CIR/Lowering/globals.cir
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Expand Up @@ -11,6 +11,7 @@
!u64i = !cir.int<u, 64>
!u8i = !cir.int<u, 8>
!ty_22struct2EA22 = !cir.struct<"struct.A", !s32i, !cir.array<!cir.array<!s32i x 2> x 2>, #cir.recdecl.ast>
!ty_22struct2EBar22 = !cir.struct<"struct.Bar", !s32i, !s8i, #cir.recdecl.ast>

module {
cir.global external @a = #cir.int<3> : !s32i
Expand Down Expand Up @@ -134,4 +135,14 @@ module {
// MLIR: llvm.mlir.global external @zeroInitFlt(dense<0.000000e+00> : tensor<2xf32>) {addr_space = 0 : i32} : !llvm.array<2 x f32>
cir.global "private" internal @staticVar = #cir.int<0> : !s32i
// MLIR: llvm.mlir.global internal @staticVar(0 : i32) {addr_space = 0 : i32} : i32
cir.global external @nullPtr = #cir.null : !cir.ptr<!s32i>
// MLIR: llvm.mlir.global external @nullPtr()
// MLIR: %0 = llvm.mlir.null : !llvm.ptr<i32>
// MLIR: llvm.return %0 : !llvm.ptr<i32>
// MLIR: }
cir.global external @zeroStruct = #cir.zero : !ty_22struct2EBar22
// MLIR: llvm.mlir.global external @zeroStruct()
// MLIR: %0 = cir.llvmir.zeroinit : !llvm.struct<"struct.Bar", (i32, i8)>
// MLIR: llvm.return %0 : !llvm.struct<"struct.Bar", (i32, i8)>
// MLIR: }
}
14 changes: 10 additions & 4 deletions clang/test/CIR/Translation/zeroinitializer.cir
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Expand Up @@ -2,12 +2,18 @@
// RUN: FileCheck --input-file=%t.ll %s

module {
// Should lower #cir.zero on structs to a zeroinitializer.
llvm.mlir.global external @bar() {addr_space = 0 : i32, cir.initial_value = #cir.zero : !llvm.struct<"struct.S", (i8, i32)>} : !llvm.struct<"struct.S", (i8, i32)>
// Should zero-initialize global structs initialized with cir.llvmir.zeroinit.
llvm.mlir.global external @bar() {addr_space = 0 : i32} : !llvm.struct<"struct.S", (i8, i32)> {
%0 = cir.llvmir.zeroinit : !llvm.struct<"struct.S", (i8, i32)>
llvm.return %0 : !llvm.struct<"struct.S", (i8, i32)>
}
// CHECK: @bar = global %struct.S zeroinitializer

// Should lower #cir.null on pointers to a null initializer.
llvm.mlir.global external @ptr() {addr_space = 0 : i32, cir.initial_value = #cir.zero : !llvm.ptr<i32>} : !llvm.ptr<i32>
// Should null-initialize global pointer initialized with cir.llvmir.zeroinit.
llvm.mlir.global external @ptr() {addr_space = 0 : i32} : !llvm.ptr<i32> {
%0 = cir.llvmir.zeroinit : !llvm.ptr<i32>
llvm.return %0 : !llvm.ptr<i32>
}
// CHECK: @ptr = global ptr null

// Should lower aggregates types with elements initialized with cir.llvmir.zeroinit.
Expand Down