diff options
| author | bors <bors@rust-lang.org> | 2025-07-21 19:48:22 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2025-07-21 19:48:22 +0000 |
| commit | 9748d87dc70a9a6725c5dbd76ce29d04752b4f90 (patch) | |
| tree | 4cffbc92abe5995b0348e464ffe6a256f973e653 /compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs | |
| parent | 3f9f20f71dd945fe7d044e274094a53c90788269 (diff) | |
| parent | 6628a4afb5d08555f09878a48f0c4179e7582aa2 (diff) | |
| download | rust-9748d87dc70a9a6725c5dbd76ce29d04752b4f90.tar.gz rust-9748d87dc70a9a6725c5dbd76ce29d04752b4f90.zip | |
Auto merge of #144269 - jieyouxu:rollup-137ysl2, r=jieyouxu
Rollup of 14 pull requests Successful merges: - rust-lang/rust#142097 (gpu offload host code generation) - rust-lang/rust#143430 (Lower extra lifetimes before normal generic params.) - rust-lang/rust#143768 (Constify Try, From, TryFrom and relevant traits) - rust-lang/rust#143816 (Implement `check` for compiletest and RA using tool macro) - rust-lang/rust#143985 (rustc_public: de-StableMIR-ize) - rust-lang/rust#144027 (clippy: make tests work in stage 1) - rust-lang/rust#144080 (Mitigate `#[align]` name resolution ambiguity regression with a rename) - rust-lang/rust#144176 (Add approval blocking labels for new bors) - rust-lang/rust#144187 (fix handling of base address for TypeId allocations) - rust-lang/rust#144212 (Remove the ptr_unique lang item) - rust-lang/rust#144243 (Subtree update of `rust-analyzer`) - rust-lang/rust#144246 (Don't use another main test file as auxiliary) - rust-lang/rust#144251 (rustc-dev-guide subtree update) - rust-lang/rust#144254 (opt-dist: make `artifact-dir` an absolute path for `opt-dist local`) r? `@ghost` `@rustbot` modify labels: rollup
Diffstat (limited to 'compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs | 439 |
1 files changed, 439 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs b/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs new file mode 100644 index 00000000000..1280ab1442a --- /dev/null +++ b/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs @@ -0,0 +1,439 @@ +use std::ffi::CString; + +use llvm::Linkage::*; +use rustc_abi::Align; +use rustc_codegen_ssa::back::write::CodegenContext; +use rustc_codegen_ssa::traits::BaseTypeCodegenMethods; + +use crate::builder::SBuilder; +use crate::common::AsCCharPtr; +use crate::llvm::AttributePlace::Function; +use crate::llvm::{self, Linkage, Type, Value}; +use crate::{LlvmCodegenBackend, SimpleCx, attributes}; + +pub(crate) fn handle_gpu_code<'ll>( + _cgcx: &CodegenContext<LlvmCodegenBackend>, + cx: &'ll SimpleCx<'_>, +) { + // The offload memory transfer type for each kernel + let mut o_types = vec![]; + let mut kernels = vec![]; + let offload_entry_ty = add_tgt_offload_entry(&cx); + for num in 0..9 { + let kernel = cx.get_function(&format!("kernel_{num}")); + if let Some(kernel) = kernel { + o_types.push(gen_define_handling(&cx, kernel, offload_entry_ty, num)); + kernels.push(kernel); + } + } + + gen_call_handling(&cx, &kernels, &o_types); +} + +// What is our @1 here? A magic global, used in our data_{begin/update/end}_mapper: +// @0 = private unnamed_addr constant [23 x i8] c";unknown;unknown;0;0;;\00", align 1 +// @1 = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 22, ptr @0 }, align 8 +fn generate_at_one<'ll>(cx: &'ll SimpleCx<'_>) -> &'ll llvm::Value { + // @0 = private unnamed_addr constant [23 x i8] c";unknown;unknown;0;0;;\00", align 1 + let unknown_txt = ";unknown;unknown;0;0;;"; + let c_entry_name = CString::new(unknown_txt).unwrap(); + let c_val = c_entry_name.as_bytes_with_nul(); + let initializer = crate::common::bytes_in_context(cx.llcx, c_val); + let at_zero = add_unnamed_global(&cx, &"", initializer, PrivateLinkage); + llvm::set_alignment(at_zero, Align::ONE); + + // @1 = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 22, ptr @0 }, align 8 + let struct_ident_ty = cx.type_named_struct("struct.ident_t"); + let struct_elems = vec![ + cx.get_const_i32(0), + cx.get_const_i32(2), + cx.get_const_i32(0), + cx.get_const_i32(22), + at_zero, + ]; + let struct_elems_ty: Vec<_> = struct_elems.iter().map(|&x| cx.val_ty(x)).collect(); + let initializer = crate::common::named_struct(struct_ident_ty, &struct_elems); + cx.set_struct_body(struct_ident_ty, &struct_elems_ty, false); + let at_one = add_unnamed_global(&cx, &"", initializer, PrivateLinkage); + llvm::set_alignment(at_one, Align::EIGHT); + at_one +} + +pub(crate) fn add_tgt_offload_entry<'ll>(cx: &'ll SimpleCx<'_>) -> &'ll llvm::Type { + let offload_entry_ty = cx.type_named_struct("struct.__tgt_offload_entry"); + let tptr = cx.type_ptr(); + let ti64 = cx.type_i64(); + let ti32 = cx.type_i32(); + let ti16 = cx.type_i16(); + // For each kernel to run on the gpu, we will later generate one entry of this type. + // copied from LLVM + // typedef struct { + // uint64_t Reserved; + // uint16_t Version; + // uint16_t Kind; + // uint32_t Flags; Flags associated with the entry (see Target Region Entry Flags) + // void *Address; Address of global symbol within device image (function or global) + // char *SymbolName; + // uint64_t Size; Size of the entry info (0 if it is a function) + // uint64_t Data; + // void *AuxAddr; + // } __tgt_offload_entry; + let entry_elements = vec![ti64, ti16, ti16, ti32, tptr, tptr, ti64, ti64, tptr]; + cx.set_struct_body(offload_entry_ty, &entry_elements, false); + offload_entry_ty +} + +fn gen_tgt_kernel_global<'ll>(cx: &'ll SimpleCx<'_>) { + let kernel_arguments_ty = cx.type_named_struct("struct.__tgt_kernel_arguments"); + let tptr = cx.type_ptr(); + let ti64 = cx.type_i64(); + let ti32 = cx.type_i32(); + let tarr = cx.type_array(ti32, 3); + + // Taken from the LLVM APITypes.h declaration: + //struct KernelArgsTy { + // uint32_t Version = 0; // Version of this struct for ABI compatibility. + // uint32_t NumArgs = 0; // Number of arguments in each input pointer. + // void **ArgBasePtrs = + // nullptr; // Base pointer of each argument (e.g. a struct). + // void **ArgPtrs = nullptr; // Pointer to the argument data. + // int64_t *ArgSizes = nullptr; // Size of the argument data in bytes. + // int64_t *ArgTypes = nullptr; // Type of the data (e.g. to / from). + // void **ArgNames = nullptr; // Name of the data for debugging, possibly null. + // void **ArgMappers = nullptr; // User-defined mappers, possibly null. + // uint64_t Tripcount = + // 0; // Tripcount for the teams / distribute loop, 0 otherwise. + // struct { + // uint64_t NoWait : 1; // Was this kernel spawned with a `nowait` clause. + // uint64_t IsCUDA : 1; // Was this kernel spawned via CUDA. + // uint64_t Unused : 62; + // } Flags = {0, 0, 0}; + // // The number of teams (for x,y,z dimension). + // uint32_t NumTeams[3] = {0, 0, 0}; + // // The number of threads (for x,y,z dimension). + // uint32_t ThreadLimit[3] = {0, 0, 0}; + // uint32_t DynCGroupMem = 0; // Amount of dynamic cgroup memory requested. + //}; + let kernel_elements = + vec![ti32, ti32, tptr, tptr, tptr, tptr, tptr, tptr, ti64, ti64, tarr, tarr, ti32]; + + cx.set_struct_body(kernel_arguments_ty, &kernel_elements, false); + // For now we don't handle kernels, so for now we just add a global dummy + // to make sure that the __tgt_offload_entry is defined and handled correctly. + cx.declare_global("my_struct_global2", kernel_arguments_ty); +} + +fn gen_tgt_data_mappers<'ll>( + cx: &'ll SimpleCx<'_>, +) -> (&'ll llvm::Value, &'ll llvm::Value, &'ll llvm::Value, &'ll llvm::Type) { + let tptr = cx.type_ptr(); + let ti64 = cx.type_i64(); + let ti32 = cx.type_i32(); + + let args = vec![tptr, ti64, ti32, tptr, tptr, tptr, tptr, tptr, tptr]; + let mapper_fn_ty = cx.type_func(&args, cx.type_void()); + let mapper_begin = "__tgt_target_data_begin_mapper"; + let mapper_update = "__tgt_target_data_update_mapper"; + let mapper_end = "__tgt_target_data_end_mapper"; + let begin_mapper_decl = declare_offload_fn(&cx, mapper_begin, mapper_fn_ty); + let update_mapper_decl = declare_offload_fn(&cx, mapper_update, mapper_fn_ty); + let end_mapper_decl = declare_offload_fn(&cx, mapper_end, mapper_fn_ty); + + let nounwind = llvm::AttributeKind::NoUnwind.create_attr(cx.llcx); + attributes::apply_to_llfn(begin_mapper_decl, Function, &[nounwind]); + attributes::apply_to_llfn(update_mapper_decl, Function, &[nounwind]); + attributes::apply_to_llfn(end_mapper_decl, Function, &[nounwind]); + + (begin_mapper_decl, update_mapper_decl, end_mapper_decl, mapper_fn_ty) +} + +fn add_priv_unnamed_arr<'ll>(cx: &SimpleCx<'ll>, name: &str, vals: &[u64]) -> &'ll llvm::Value { + let ti64 = cx.type_i64(); + let mut size_val = Vec::with_capacity(vals.len()); + for &val in vals { + size_val.push(cx.get_const_i64(val)); + } + let initializer = cx.const_array(ti64, &size_val); + add_unnamed_global(cx, name, initializer, PrivateLinkage) +} + +pub(crate) fn add_unnamed_global<'ll>( + cx: &SimpleCx<'ll>, + name: &str, + initializer: &'ll llvm::Value, + l: Linkage, +) -> &'ll llvm::Value { + let llglobal = add_global(cx, name, initializer, l); + llvm::LLVMSetUnnamedAddress(llglobal, llvm::UnnamedAddr::Global); + llglobal +} + +pub(crate) fn add_global<'ll>( + cx: &SimpleCx<'ll>, + name: &str, + initializer: &'ll llvm::Value, + l: Linkage, +) -> &'ll llvm::Value { + let c_name = CString::new(name).unwrap(); + let llglobal: &'ll llvm::Value = llvm::add_global(cx.llmod, cx.val_ty(initializer), &c_name); + llvm::set_global_constant(llglobal, true); + llvm::set_linkage(llglobal, l); + llvm::set_initializer(llglobal, initializer); + llglobal +} + +fn gen_define_handling<'ll>( + cx: &'ll SimpleCx<'_>, + kernel: &'ll llvm::Value, + offload_entry_ty: &'ll llvm::Type, + num: i64, +) -> &'ll llvm::Value { + let types = cx.func_params_types(cx.get_type_of_global(kernel)); + // It seems like non-pointer values are automatically mapped. So here, we focus on pointer (or + // reference) types. + let num_ptr_types = types + .iter() + .map(|&x| matches!(cx.type_kind(x), rustc_codegen_ssa::common::TypeKind::Pointer)) + .count(); + + // We do not know their size anymore at this level, so hardcode a placeholder. + // A follow-up pr will track these from the frontend, where we still have Rust types. + // Then, we will be able to figure out that e.g. `&[f32;256]` will result in 4*256 bytes. + // I decided that 1024 bytes is a great placeholder value for now. + add_priv_unnamed_arr(&cx, &format!(".offload_sizes.{num}"), &vec![1024; num_ptr_types]); + // Here we figure out whether something needs to be copied to the gpu (=1), from the gpu (=2), + // or both to and from the gpu (=3). Other values shouldn't affect us for now. + // A non-mutable reference or pointer will be 1, an array that's not read, but fully overwritten + // will be 2. For now, everything is 3, until we have our frontend set up. + let o_types = + add_priv_unnamed_arr(&cx, &format!(".offload_maptypes.{num}"), &vec![3; num_ptr_types]); + // Next: For each function, generate these three entries. A weak constant, + // the llvm.rodata entry name, and the omp_offloading_entries value + + let name = format!(".kernel_{num}.region_id"); + let initializer = cx.get_const_i8(0); + let region_id = add_unnamed_global(&cx, &name, initializer, WeakAnyLinkage); + + let c_entry_name = CString::new(format!("kernel_{num}")).unwrap(); + let c_val = c_entry_name.as_bytes_with_nul(); + let offload_entry_name = format!(".offloading.entry_name.{num}"); + + let initializer = crate::common::bytes_in_context(cx.llcx, c_val); + let llglobal = add_unnamed_global(&cx, &offload_entry_name, initializer, InternalLinkage); + llvm::set_alignment(llglobal, Align::ONE); + llvm::set_section(llglobal, c".llvm.rodata.offloading"); + + // Not actively used yet, for calling real kernels + let name = format!(".offloading.entry.kernel_{num}"); + + // See the __tgt_offload_entry documentation above. + let reserved = cx.get_const_i64(0); + let version = cx.get_const_i16(1); + let kind = cx.get_const_i16(1); + let flags = cx.get_const_i32(0); + let size = cx.get_const_i64(0); + let data = cx.get_const_i64(0); + let aux_addr = cx.const_null(cx.type_ptr()); + let elems = vec![reserved, version, kind, flags, region_id, llglobal, size, data, aux_addr]; + + let initializer = crate::common::named_struct(offload_entry_ty, &elems); + let c_name = CString::new(name).unwrap(); + let llglobal = llvm::add_global(cx.llmod, offload_entry_ty, &c_name); + llvm::set_global_constant(llglobal, true); + llvm::set_linkage(llglobal, WeakAnyLinkage); + llvm::set_initializer(llglobal, initializer); + llvm::set_alignment(llglobal, Align::ONE); + let c_section_name = CString::new(".omp_offloading_entries").unwrap(); + llvm::set_section(llglobal, &c_section_name); + o_types +} + +fn declare_offload_fn<'ll>( + cx: &'ll SimpleCx<'_>, + name: &str, + ty: &'ll llvm::Type, +) -> &'ll llvm::Value { + crate::declare::declare_simple_fn( + cx, + name, + llvm::CallConv::CCallConv, + llvm::UnnamedAddr::No, + llvm::Visibility::Default, + ty, + ) +} + +// For each kernel *call*, we now use some of our previous declared globals to move data to and from +// the gpu. We don't have a proper frontend yet, so we assume that every call to a kernel function +// from main is intended to run on the GPU. For now, we only handle the data transfer part of it. +// If two consecutive kernels use the same memory, we still move it to the host and back to the gpu. +// Since in our frontend users (by default) don't have to specify data transfer, this is something +// we should optimize in the future! We also assume that everything should be copied back and forth, +// but sometimes we can directly zero-allocate on the device and only move back, or if something is +// immutable, we might only copy it to the device, but not back. +// +// Current steps: +// 0. Alloca some variables for the following steps +// 1. set insert point before kernel call. +// 2. generate all the GEPS and stores, to be used in 3) +// 3. generate __tgt_target_data_begin calls to move data to the GPU +// +// unchanged: keep kernel call. Later move the kernel to the GPU +// +// 4. set insert point after kernel call. +// 5. generate all the GEPS and stores, to be used in 6) +// 6. generate __tgt_target_data_end calls to move data from the GPU +fn gen_call_handling<'ll>( + cx: &'ll SimpleCx<'_>, + _kernels: &[&'ll llvm::Value], + o_types: &[&'ll llvm::Value], +) { + // %struct.__tgt_bin_desc = type { i32, ptr, ptr, ptr } + let tptr = cx.type_ptr(); + let ti32 = cx.type_i32(); + let tgt_bin_desc_ty = vec![ti32, tptr, tptr, tptr]; + let tgt_bin_desc = cx.type_named_struct("struct.__tgt_bin_desc"); + cx.set_struct_body(tgt_bin_desc, &tgt_bin_desc_ty, false); + + gen_tgt_kernel_global(&cx); + let (begin_mapper_decl, _, end_mapper_decl, fn_ty) = gen_tgt_data_mappers(&cx); + + let main_fn = cx.get_function("main"); + let Some(main_fn) = main_fn else { return }; + let kernel_name = "kernel_1"; + let call = unsafe { + llvm::LLVMRustGetFunctionCall(main_fn, kernel_name.as_c_char_ptr(), kernel_name.len()) + }; + let Some(kernel_call) = call else { + return; + }; + let kernel_call_bb = unsafe { llvm::LLVMGetInstructionParent(kernel_call) }; + let called = unsafe { llvm::LLVMGetCalledValue(kernel_call).unwrap() }; + let mut builder = SBuilder::build(cx, kernel_call_bb); + + let types = cx.func_params_types(cx.get_type_of_global(called)); + let num_args = types.len() as u64; + + // Step 0) + // %struct.__tgt_bin_desc = type { i32, ptr, ptr, ptr } + // %6 = alloca %struct.__tgt_bin_desc, align 8 + unsafe { llvm::LLVMRustPositionBuilderPastAllocas(builder.llbuilder, main_fn) }; + + let tgt_bin_desc_alloca = builder.direct_alloca(tgt_bin_desc, Align::EIGHT, "EmptyDesc"); + + let ty = cx.type_array(cx.type_ptr(), num_args); + // Baseptr are just the input pointer to the kernel, stored in a local alloca + let a1 = builder.direct_alloca(ty, Align::EIGHT, ".offload_baseptrs"); + // Ptrs are the result of a gep into the baseptr, at least for our trivial types. + let a2 = builder.direct_alloca(ty, Align::EIGHT, ".offload_ptrs"); + // These represent the sizes in bytes, e.g. the entry for `&[f64; 16]` will be 8*16. + let ty2 = cx.type_array(cx.type_i64(), num_args); + let a4 = builder.direct_alloca(ty2, Align::EIGHT, ".offload_sizes"); + // Now we allocate once per function param, a copy to be passed to one of our maps. + let mut vals = vec![]; + let mut geps = vec![]; + let i32_0 = cx.get_const_i32(0); + for (index, in_ty) in types.iter().enumerate() { + // get function arg, store it into the alloca, and read it. + let p = llvm::get_param(called, index as u32); + let name = llvm::get_value_name(p); + let name = str::from_utf8(&name).unwrap(); + let arg_name = format!("{name}.addr"); + let alloca = builder.direct_alloca(in_ty, Align::EIGHT, &arg_name); + + builder.store(p, alloca, Align::EIGHT); + let val = builder.load(in_ty, alloca, Align::EIGHT); + let gep = builder.inbounds_gep(cx.type_f32(), val, &[i32_0]); + vals.push(val); + geps.push(gep); + } + + // Step 1) + unsafe { llvm::LLVMRustPositionBefore(builder.llbuilder, kernel_call) }; + builder.memset(tgt_bin_desc_alloca, cx.get_const_i8(0), cx.get_const_i64(32), Align::EIGHT); + + let mapper_fn_ty = cx.type_func(&[cx.type_ptr()], cx.type_void()); + let register_lib_decl = declare_offload_fn(&cx, "__tgt_register_lib", mapper_fn_ty); + let unregister_lib_decl = declare_offload_fn(&cx, "__tgt_unregister_lib", mapper_fn_ty); + let init_ty = cx.type_func(&[], cx.type_void()); + let init_rtls_decl = declare_offload_fn(cx, "__tgt_init_all_rtls", init_ty); + + // call void @__tgt_register_lib(ptr noundef %6) + builder.call(mapper_fn_ty, register_lib_decl, &[tgt_bin_desc_alloca], None); + // call void @__tgt_init_all_rtls() + builder.call(init_ty, init_rtls_decl, &[], None); + + for i in 0..num_args { + let idx = cx.get_const_i32(i); + let gep1 = builder.inbounds_gep(ty, a1, &[i32_0, idx]); + builder.store(vals[i as usize], gep1, Align::EIGHT); + let gep2 = builder.inbounds_gep(ty, a2, &[i32_0, idx]); + builder.store(geps[i as usize], gep2, Align::EIGHT); + let gep3 = builder.inbounds_gep(ty2, a4, &[i32_0, idx]); + // As mentioned above, we don't use Rust type information yet. So for now we will just + // assume that we have 1024 bytes, 256 f32 values. + // FIXME(offload): write an offload frontend and handle arbitrary types. + builder.store(cx.get_const_i64(1024), gep3, Align::EIGHT); + } + + // For now we have a very simplistic indexing scheme into our + // offload_{baseptrs,ptrs,sizes}. We will probably improve this along with our gpu frontend pr. + fn get_geps<'a, 'll>( + builder: &mut SBuilder<'a, 'll>, + cx: &'ll SimpleCx<'ll>, + ty: &'ll Type, + ty2: &'ll Type, + a1: &'ll Value, + a2: &'ll Value, + a4: &'ll Value, + ) -> (&'ll Value, &'ll Value, &'ll Value) { + let i32_0 = cx.get_const_i32(0); + + let gep1 = builder.inbounds_gep(ty, a1, &[i32_0, i32_0]); + let gep2 = builder.inbounds_gep(ty, a2, &[i32_0, i32_0]); + let gep3 = builder.inbounds_gep(ty2, a4, &[i32_0, i32_0]); + (gep1, gep2, gep3) + } + + fn generate_mapper_call<'a, 'll>( + builder: &mut SBuilder<'a, 'll>, + cx: &'ll SimpleCx<'ll>, + geps: (&'ll Value, &'ll Value, &'ll Value), + o_type: &'ll Value, + fn_to_call: &'ll Value, + fn_ty: &'ll Type, + num_args: u64, + s_ident_t: &'ll Value, + ) { + let nullptr = cx.const_null(cx.type_ptr()); + let i64_max = cx.get_const_i64(u64::MAX); + let num_args = cx.get_const_i32(num_args); + let args = + vec![s_ident_t, i64_max, num_args, geps.0, geps.1, geps.2, o_type, nullptr, nullptr]; + builder.call(fn_ty, fn_to_call, &args, None); + } + + // Step 2) + let s_ident_t = generate_at_one(&cx); + let o = o_types[0]; + let geps = get_geps(&mut builder, &cx, ty, ty2, a1, a2, a4); + generate_mapper_call(&mut builder, &cx, geps, o, begin_mapper_decl, fn_ty, num_args, s_ident_t); + + // Step 3) + // Here we will add code for the actual kernel launches in a follow-up PR. + // FIXME(offload): launch kernels + + // Step 4) + unsafe { llvm::LLVMRustPositionAfter(builder.llbuilder, kernel_call) }; + + let geps = get_geps(&mut builder, &cx, ty, ty2, a1, a2, a4); + generate_mapper_call(&mut builder, &cx, geps, o, end_mapper_decl, fn_ty, num_args, s_ident_t); + + builder.call(mapper_fn_ty, unregister_lib_decl, &[tgt_bin_desc_alloca], None); + + // With this we generated the following begin and end mappers. We could easily generate the + // update mapper in an update. + // call void @__tgt_target_data_begin_mapper(ptr @1, i64 -1, i32 3, ptr %27, ptr %28, ptr %29, ptr @.offload_maptypes, ptr null, ptr null) + // call void @__tgt_target_data_update_mapper(ptr @1, i64 -1, i32 2, ptr %46, ptr %47, ptr %48, ptr @.offload_maptypes.1, ptr null, ptr null) + // call void @__tgt_target_data_end_mapper(ptr @1, i64 -1, i32 3, ptr %49, ptr %50, ptr %51, ptr @.offload_maptypes, ptr null, ptr null) +} |
