[CIR] Upstream new SetBitfieldOp for handling C and C++ struct bitfields #147609
There are no files selected for viewing
| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
|
@@ -1669,6 +1669,94 @@ def GetGlobalOp : CIR_Op<"get_global", | |
| }]; | ||
| } | ||
|
|
||
| //===----------------------------------------------------------------------===// | ||
| // SetBitfieldOp | ||
| //===----------------------------------------------------------------------===// | ||
|
|
||
| def SetBitfieldOp : CIR_Op<"set_bitfield"> { | ||
| let summary = "Set the value of a bitfield member"; | ||
| let description = [{ | ||
| The `cir.set_bitfield` operation provides a store-like access to | ||
| a bit field of a record. | ||
|
|
||
| A bitfield info attribute must be provided to describe the location of | ||
| the bitfield within the memory referenced by the $addr argument. | ||
| The $src argument is inserted at the appropriate place in the memory and | ||
| the value that was stored. Returns a value being stored. | ||
|
|
||
| A unit attribute `volatile` can be used to indicate a volatile store of the | ||
| bitfield. | ||
| ```mlir | ||
| cir.set_bitfield(#bfi, %0 : !cir.ptr<!u32i>, %1 : !s32i) {is_volatile} | ||
| -> !s32i | ||
| ``` | ||
|
|
||
| Example. | ||
| Suppose we have a struct with multiple bitfields stored in | ||
| different storages. The `cir.set_bitfield` operation sets the value | ||
| of the bitfield. | ||
| ```C++ | ||
| typedef struct { | ||
| int a : 4; | ||
| int b : 27; | ||
| int c : 17; | ||
| int d : 2; | ||
| int e : 15; | ||
| } S; | ||
|
|
||
| void store_bitfield(S& s) { | ||
| s.e = 3; | ||
| } | ||
| ``` | ||
|
|
||
| ```mlir | ||
| // 'e' is in the storage with the index 1 | ||
| !record_type = !cir.record<struct "S" packed padded {!u64i, !u16i, | ||
| !cir.array<!u8i x 2>} #cir.record.decl.ast> | ||
| #bfi_e = #cir.bitfield_info<name = "e", storage_type = !u16i, size = 15, | ||
| offset = 0, is_signed = true> | ||
|
|
||
| %1 = cir.const #cir.int<3> : !s32i | ||
| %2 = cir.load %0 : !cir.ptr<!cir.ptr<!record_type>>, !cir.ptr<!record_type> | ||
| %3 = cir.get_member %2[1] {name = "e"} : !cir.ptr<!record_type> | ||
| -> !cir.ptr<!u16i> | ||
| %4 = cir.set_bitfield(#bfi_e, %3 : !cir.ptr<!u16i>, %1 : !s32i) -> !s32i | ||
|
Member
There was a problem hiding this comment. Perhaps we should introduce this one without the parens for args? See https://llvm.github.io/clangir/Dialect/cir-style-guide.html
Contributor
Author
There was a problem hiding this comment. Should it be written like this, with a comma after the attribute? cir.set_bitfield #bfi_e, %3, %1 : (!cir.ptr<!u16i>, !s32i) -> !s32iOr without the comma? cir.set_bitfield #bfi_e %3, %1 : (!cir.ptr<!u16i>, !s32i) -> !s32iAnd should we also update |
||
| ``` | ||
| }]; | ||
|
|
||
| let arguments = (ins | ||
| Arg<CIR_PointerType, "the address to store the value", [MemWrite]>:$addr, | ||
| CIR_AnyType:$src, | ||
| BitfieldInfoAttr:$bitfield_info, | ||
| UnitAttr:$is_volatile | ||
| ); | ||
|
|
||
| let results = (outs CIR_IntType:$result); | ||
|
Contributor
There was a problem hiding this comment. Is the result of this operation ever used? If so, where?
Contributor
Author
There was a problem hiding this comment. Yes, I noticed that too the return value from the function llvm-project/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp Lines 955 to 961 in 071e302 llvm-project/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp Lines 977 to 980 in 071e302
Contributor
Author
There was a problem hiding this comment. It is also used in the incubator: In the incubator, the result was passed as the
Contributor
There was a problem hiding this comment. I see that you're right. Can you add a test case where the return value is used? This looks like it does that in C (though not in C++):
Contributor
Author
There was a problem hiding this comment. Ok, it would also be used in the case of a unary operation when it is upstream. void unOp(S* s) {
s->c++;
} |
||
|
|
||
| let assemblyFormat = [{ `(`$bitfield_info`,` $addr`:`qualified(type($addr))`,` | ||
| $src`:`type($src) `)` attr-dict `->` type($result) }]; | ||
|
|
||
| let builders = [ | ||
| OpBuilder<(ins "mlir::Type":$type, | ||
| "mlir::Value":$addr, | ||
| "mlir::Type":$storage_type, | ||
| "mlir::Value":$src, | ||
| "llvm::StringRef":$name, | ||
| "unsigned":$size, | ||
| "unsigned":$offset, | ||
| "bool":$is_signed, | ||
| "bool":$is_volatile | ||
| ), | ||
| [{ | ||
| BitfieldInfoAttr info = | ||
| BitfieldInfoAttr::get($_builder.getContext(), | ||
| name, storage_type, | ||
| size, offset, is_signed); | ||
| build($_builder, $_state, type, addr, src, info, is_volatile); | ||
| }]> | ||
| ]; | ||
| } | ||
|
|
||
| //===----------------------------------------------------------------------===// | ||
| // GetBitfieldOp | ||
| //===----------------------------------------------------------------------===// | ||
|
|
||
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
Done