[cir] [Lowering] Handle VaArg #1088
Open
+149,087
−184
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This is currently crashing on Linux only internally, but not on GitHub's CI, disable it temporarily while we investigate.
This is a straightforward adaption of existing CodeGen logic. While I'm here, move block comments inside their blocks, so that they look nicer.
…VM (llvm#810) As title. Add setAlignmentAttr for GlobalOps created from AST. LLVM Lowering should have LLVM GlobalOp's alignment attribute inherited from CIR::GlobalOp. This PR is definitely needed to fix issue llvm#801 (comment), but the issue doesn't have alignment and comdat attribute for CIR Ops to begin with, so I'll keep investigating and fix CIR problem in another PR.
…y cast op (llvm#812) There are two occurrences of `cir.cast(array_to_ptrdecay, ...)` that drop address spaces unexpectedly for its result pointer type. This PR fixes them with the source address space. ```mlir // Before %1 = cir.cast(array_to_ptrdecay, %0 : !cir.ptr<!cir.array<!s32i x 32>, addrspace(offload_local)>), !cir.ptr<!s32i> // After %1 = cir.cast(array_to_ptrdecay, %0 : !cir.ptr<!cir.array<!s32i x 32>, addrspace(offload_local)>), !cir.ptr<!s32i, addrspace(offload_local)> ```
As mentioned at llvm#809 (comment) , this PR adds more simplify transformations for select op: - `cir.select if %0 then x else x` -> `x` - `cir.select if %0 then #true else #false` -> `%0` - `cir.select if %0 then #false else #true` -> `cir.unary not %0`
…p ops (llvm#818) This PR makes simple lowering generate the result type lowering logic and make it suitable for unary fp2int operations and binary fp2fp operations.
…ization (llvm#820) This PR adds initial support for temporary materialization of local temporaries with trivial cleanups. Materialization of global temporaries and local temporaries with non-trivial cleanups is far more trickier that I initially thought and I decide to submit this easy part first.
This is a straightforward adaption from CodeGen. I checked the uses of the Delegating arg that's passed in various places, and it only appears to be used by virtual inheritance, which should be handled by llvm#624.
…on (llvm#813) Currently some bitcasts would silently change the address space of source pointer type, which hides some miscompilations of pointer type in CIR. llvm#812 is an example. The address space in result pointer type is dropped, but the bitcast later keep the type consistency no matter what the result type is. Such bitcast is commonly emitted in CodeGen. CIR bitcasts are lowered to LLVM bitcasts, which also don't allow mismatch between address spaces. This PR adds this verification.
We were previously printing the type alias for `struct S` as `!ty_22S22`
instead of just `!ty_S`. This was because our alias computation for a
StructType did the following:
os << "ty_" << structType.getName()
`structType.getName()` is a `StringAttr`, and writing a `StringAttr` to
an output stream adds double quotes around the actual string [1][2].
These double quotes then get hex-encoded as 22 [3].
We can fix this by writing the actual string value instead. Aliases that
would end in a number will now receive a trailing underscore because of
MLIR's alias sanitization not allowing a trailing digit [4] (which
ironically didn't kick in even though our aliases were always previously
ending with a number, which might be a bug in the sanitization logic).
Aliases containing other special characters (e.g. `::`) will still be
escaped as before. In other words:
```
struct S {};
// before: !ty_22S22 = ...
// after: !ty_S = ...
struct S1 {};
// before: !ty_22S122 = ...
// after: !ty_S1_ = ...
struct std::string {};
// before: !ty_22std3A3Astring22
// after: !ty_std3A3Astring
```
I'm not a big fan of the trailing underscore special-case, but I also
don't want to touch core MLIR logic, and I think the end result is still
nicer than before.
The tests were mechanically updated with the following command run
inside `clang/test/CIR`, and the same commands can be run to update the
tests for any in-flight patches. (These are for GNU sed; for macOS
change the `-i` to `-i ''`.)
find . -type f | xargs sed -i -E -e
's/ty_22([A-Za-z0-9_$]+[0-9])22/ty_\1_/g' -e
's/ty_22([A-Za-z0-9_$]+)22/ty_\1/g'
clang/test/CIR/CodeGen/stmtexpr-init.c needed an additional minor fix to
swap the expected order of two type aliases in the CIR output.
clang/test/CIR/CodeGen/coro-task.cpp needed some surgery because it was
searching for `22` to find the end of a type alias; I changed it to
search for the actual alias instead.
If you run into merge conflicts after this change, you can auto-resolve
them via
smeenai@715f061
[1]
https://github.com/llvm/llvm-project/blob/b3d2d5039b9b8aa10a86c593387f200b15c02aef/mlir/lib/IR/AsmPrinter.cpp#L2295
[2]
https://github.com/llvm/llvm-project/blob/b3d2d5039b9b8aa10a86c593387f200b15c02aef/mlir/lib/IR/AsmPrinter.cpp#L2763
[3]
https://github.com/llvm/llvm-project/blob/b3d2d5039b9b8aa10a86c593387f200b15c02aef/mlir/lib/IR/AsmPrinter.cpp#L1014
[4]
https://github.com/llvm/llvm-project/blob/b3d2d5039b9b8aa10a86c593387f200b15c02aef/mlir/lib/IR/AsmPrinter.cpp#L1154
This PR fixes the lowering for BrCond.
Consider the following code snippet:
```
#include <stdbool.h>
bool test() {
bool x = false;
if (x)
return x;
return x;
}
```
Emitting the CIR to `tmp.cir` using `-fclangir-mem2reg` produces the
following CIR (truncated):
```
!s32i = !cir.int<s, 32>
#fn_attr = #cir<extra({inline = #cir.inline<no>, nothrow = #cir.nothrow, optnone = #cir.optnone})>
module { cir.func no_proto @test() -> !cir.bool extra(#fn_attr) {
%0 = cir.const #cir.int<0> : !s32i
%1 = cir.cast(int_to_bool, %0 : !s32i), !cir.bool
cir.br ^bb1
^bb1: // pred: ^bb0
cir.brcond %1 ^bb2, ^bb3
^bb2: // pred: ^bb1
cir.return %1 : !cir.bool
^bb3: // pred: ^bb1
cir.br ^bb4
^bb4: // pred: ^bb3
cir.return %1 : !cir.bool
}
}
```
Lowering the CIR to LLVM using `cir-opt tmp.cir -cir-to-llvm` fails
with:
```
tmp.cir:5:10: error: failed to legalize operation 'llvm.zext' marked as erased
```
The CIR cast `%1 = cir.cast(int_to_bool, %0 : !s32i)` is lowered to a
CIR comparison with zero, which is then lowered to an `LLVM::ICmpOp` and
`LLVM::ZExtOp`.
In the BrCond lowering, the zext is deleted when `zext->use_empty()`,
but during this phase the lowering for the CIR above is not complete
yet, because the zext will still have usage(s) later.
The current check for when the zext is deleted is error-prone and can be
improved.
To fix this, in addition to checking that the use of the zext is empty,
an additional check that the defining operation for the BrCond in the
CIR (the cast operation in this case) is used exactly once is added.
We haven't been able to find the root cause of llvm#829 just yet, the problem does also not show up under a ASANified build. Add some extra information before we crash, hopefully that might shed some light.
…m#822) Allow from the clang driver the use of lowering from CIR to MLIR standard dialect. Update the test to match the real output when `-fno-clangir-direct-lowering` is used, or with a combination of both `-fclangir-direct-lowering` and `-fno-clangir-direct-lowering`. --------- Co-authored-by: Bruno Cardoso Lopes <[email protected]> Co-authored-by: Shoaib Meenai <[email protected]>
We can now get the cleanup right for other potential throwing ctors, still missing LLVM lowering support.
This PR adds a new transformation that transform suitable ternary operations into select operations. Currently the "suitable" ternary operations are those ternary operations whose both branches satisfy either one of the following criteria: - The branch only contain a single `cir.yield` operation; - The branch contains a `cir.const` followed by a `cir.yield` that yields the constant value produced by the `cir.const`. - ~~The branch contains a `cir.load` followed by a `cir.yield` that yields the value loaded by the `cir.load`. The load operation cannot be volatile and must load from an alloca.~~ These criteria are hardcoded now so that simple C/C++ ternary expressions could be eventually lowered to a `cir.select` operation instead.
This is permitted by the language, and IRGen emits traps for destructors other than the base object destructor. Make CIRGen follow suit.
) The first patch to fix llvm#803 . This PR adds the calling convention attribute to CallOp directly, which is similar to LLVM, rather than adding the information to function type, which mimics Clang AST function type. The syntax of it in CIR assembly is between the function type and extra attributes, as follows: ```mlir %1 = cir.call %fnptr(%a) : (!fnptr, !s32i) -> !s32i cc(spir_kernel) extra(#fn_attr) ``` The verification of direct calls is not included. It will be included in the next patch extending CIRGen & Lowering. --- For every builder method of Call Op, an optional parameter `callingConv` is inserted right before the parameter of extra attribute. However, apart from the parser / printer, this PR does not introduce any functional changes.
… go into entry block
FlattenCFG will soon get the necessary support for lowering to LLVM, this is CIRGen only for now.
…`constructAttributeList` (llvm#831) Similar to llvm#830 , this PR completes the `setCIRFunctionAttributes` part with the call to `constructAttributeList` method, so that func op and call op share the logic of handling these kinds of attributes, which is the design of OG CodeGen. It also includes other refactors. The function `constructAttributeList` now use `mlir::NamedAttrList &` rather than immutable attribute `mlir::DictionaryAttr &` as the inout result parameter, which benefits the additive merging of attributes.
…ith OG (llvm#830) Previously the body of `setExtraAttributesForFunc` corresponds to `SetLLVMFunctionAttributesForDefinition`, but the callsite of it does not reside at the right position. This PR rename it and adjust the calls to it following OG CodeGen. To be specific, `setExtraAttributesForFunc` is called right after the initialization of `FuncOp`. But in OG CodeGen, the list of attributes is constructed by several more functions: `SetLLVMFunctionAttributes` and `SetLLVMFunctionAttributesForDefinition`. This results in diff in attributes of function declarations, which is reflected by the changes of test files. Apart from them, there is no functional change. In other words, the two code path calling `setCIRFunctionAttributesForDefinition` are tested by existing tests: * Caller `buildGlobalFunctionDefinition`: tested by `CIR/CodeGen/function-attrs.cpp`, ... * Caller `codegenCXXStructor`: tested by `CIR/CodeGen/delegating-ctor.cpp`, `defined-pure-virtual-func.cpp`, ...
The parser was looking for extra(...) before the return type while the pretty-printer put it after the return type. This was breaking the LSP-server for example. Change the parser behavior accordingly.
…#836) This PR implements the CIRGen and Lowering part of calling convention attribute of `cir.call`-like operations. Here we have **4 kinds of operations**: (direct or indirect) x (`call` or `try_call`). According to our need and feasibility of constructing a test case, this PR includes: * For CIRGen, only direct `call`. Until now, the only extra calling conventions are SPIR ones, which cannot be set from source code manually using attributes. Meanwhile, OpenCL C *does not allow* function pointers or exceptions, therefore the only case remaining is direct call. * For Lowering, direct and indirect `call`, but not any `try_call`. Although it's possible to write all 4 kinds of calls with calling convention in ClangIR assembly, exceptions is quite hard to write and read. I prefer source-code-level test for it when it's available in the future. For example, possibly C++ `thiscall` with exceptions. * Extra: the verification of calling convention consistency for direct `call` and direct `try_call`. All unsupported cases are guarded by assertions or MLIR diags.
Consider the following code snippet `test.c`:
```
int test(int x) {
static int arr[10] = {0, 1, 0, 0};
return arr[x];
}
```
When lowering from CIR to LLVM using `bin/clang test.c -Xclang -fclangir
-Xclang -emit-llvm -S -o -` It produces:
```
clangir/mlir/lib/IR/BuiltinAttributes.cpp:1015: static mlir::DenseElementsAttr mlir::DenseElementsAttr::get(mlir::ShapedType, llvm::ArrayRef<llvm::APInt>): Assertion `hasSameElementsOrSplat(type, values)' failed.
```
I traced the bug back to `Lowering/LoweringHelpers.cpp` where we fill
trailing zeros, and I believe this PR does it the right way. I have also
added a very simple test for verification.
The main purpose of this PR is to add support for C/C++ attribute
annotate. The PR involves both CIR generation and Lowering Prepare. In
the rest of this description, we first introduce the concept of
attribute annotate, then talk about expectations of LLVM regarding
annotation, after it, we describe how ClangIR handles it in this PR.
Finally, we list trivial differences between LLVM code generated by
clang codegen and ClangIR codegen.
**The concept of attribute annotate. and expected LLVM IR**
the following is C code example of annotation.
say in example.c
`int *b __attribute__((annotate("withargs", "21", 12 )));
int *a __attribute__((annotate("oneargs", "21", )));
int *c __attribute__((annotate("noargs")));
`
here "withargs" is the annotation string, "21" and 12 are arguments for
this annotation named "withargs". LLVM-based compiler is expected keep
these information and build a global variable capturing all annotations
used in the translation unit when emitting into LLVM IR. This global
variable itself is **not** constant, but will be initialized with
constants that are related to annotation representation, e.g. "withargs"
should be literal string variable in IR.
This global variable has a fixed name "llvm.global.annotations", and its
of array of struct type, and should be initialized with a const array of
const structs, each const struct is a representation of an annotation
site, which has 5-field.
[ptr to global var/func annotated, ptr to translation unit string const,
line_no, annotation_name, ptr to arguments const]
annotation name string and args constants, as well as this global var
should be in section "llvm.metadata".
e.g. In the above example,
We shall have following in the generated LLVM IR like the following
```
@b = global ptr null, align 8
@.str = private unnamed_addr constant [9 x i8] c"withargs\00", section "llvm.metadata"
@.str.1 = private unnamed_addr constant [10 x i8] c"example.c\00", section "llvm.metadata"
@.str.2 = private unnamed_addr constant [3 x i8] c"21\00", align 1
@.args = private unnamed_addr constant { ptr, i32 } { ptr @.str.2, i32 12 }, section "llvm.metadata"
@A = global ptr null, align 8
@.str.3 = private unnamed_addr constant [8 x i8] c"oneargs\00", section "llvm.metadata"
@.args.4 = private unnamed_addr constant { ptr } { ptr @.str.2 }, section "llvm.metadata"
@c = global ptr null, align 8
@.str.5 = private unnamed_addr constant [7 x i8] c"noargs\00", section "llvm.metadata"
@llvm.global.annotations = appending global [3 x { ptr, ptr, ptr, i32, ptr }] [{ ptr, ptr, ptr, i32, ptr } { ptr @b, ptr @.str, ptr @.str.1, i32 1, ptr @.args }, { ptr, ptr, ptr, i32, ptr } { ptr @A, ptr @.str.3, ptr @.str.1, i32 2, ptr @.args.4 }, { ptr, ptr, ptr, i32, ptr } { ptr @c, ptr @.str.5, ptr @.str.1, i32 3, ptr null }], section "llvm.metadata"
```
notice that since variable c's annotation has no arg, the last field of
its corresponding annotation entry is a nullptr.
**ClangIR's handling of annotations**
In CIR, we introduce AnnotationAttr to GlobalOp and FuncOp to record its
annotations. That way, we are able to make fast query about annotation
if in future a CIR pass is interested in them.
We leave the work of generating const variables as well as global
annotations' var to LLVM lowering. But at LoweringPrepare we collect all
annotations and create a module attribute "cir.global_annotations" so to
facilitate LLVM lowering.
**Some implementation details and trivial differences between clangir
generated LLVM code and vanilla LLVM code**
1. I suffix names of constants generated for annotation purpose with
".annotation" to avoid redefinition, but clang codegen doesn't do it.
3. clang codegen seems to visit FuncDecls in slightly different orders
than CIR, thus, sometimes the order of elements of the initial value
const array for llvm.global.annotations var is different from clang
generated LLVMIR, it should be trivial, as I don't expect consumer of
this var is assuming a fixed order of collecting annotations.
Otherwise, clang codegen and clangir pretty much generate same LLVM IR
for annotations!
Now that the basic is working, start adding cleanups to be attached to cir.call's instead. This is necessary in order to tie the pieces (landing pads and cleanups) more properly, allowing multiple calls inside cir.try op to be connected with the right cleanup. This is the first piece of a series, tests coming next.
fix llvm#1057 --------- Co-authored-by: Bruno Cardoso Lopes <[email protected]> Co-authored-by: Sirui Mu <[email protected]>
…memory (llvm#1059) This PR covers one more case for return values of struct type, where `memcpy` is emitted.
This PR adds LLVMIR lowering support for `cir.assume`, `cir.assume.aligned`, and `cir.assume.separate_storage`.
In OG CodeGen, string literals has `private` linkage as default (marked by `cir_private` in CIR assembly). But CIR uses `internal`, which is probably an ancient typo. This PR keeps align with it and thus modifies the existing test files.
…bits (llvm#1068) This PR adds a partial support for so-called indirect function arguments for struct types with size > 128 bits for aarch64. #### Couple words about the implementation The hard part is that it's not one-to-one copy from the original codegen, but the code is inspired by it of course. In the original codegen there is no much job is done for the indirect arguments inside the loop in the `EmitFunctionProlog`, and additional alloca is added in the end, in the call for `EmitParamDecl` function. In our case, for the indirect argument (which is a pointer) we replace the original alloca with a new one, and store the pointer in there. And replace all the uses of the old alloca with the load from the new one, i.e. in both cases users works with the pointer to a structure. Also, I added several missed features in the `constructAttributeList` for indirect arguments, but didn't preserve the original code structure, so let me know if I need to do it.
Note that we lack two pieces of support for aliases in LLVM IR dialect globals: the `alias` keyword and function types `void (ptr)`, this needs to be done before we can nail this for good, but it's outside the scope of this commit. The behavior is slightly different under -O1, which will be addressed next.
…m#1073) This PR changes the naming format of string literals from `.str1` to `.str.1`, making it easier to reuse the existing testcases of OG CodeGen.
It's currently polluting the `cir` namespace with very generic symbols like `Integer` and `Memory`, which is pretty confusing. `X86_64ABIInfo` already has `Class` alias for `X86ArgClass`, so we can use that alias to qualify all uses.
Note that there are still missing pieces, which will be incrementally addressed.
Just verified this is actually done by some LLVM optimization, not by the frontend emitting directly, so this is a non-goal now, since CIR can also use LLVM opts to do the same once we have real global alias.
Also verified this does not apply anymore, we match -O0. The only remaing part is to lower to proper LLVM globals once LLVM IR dialect gets the global alias support.
|
Hey, thanks for making progress here.
If other targets use it and x86_64 doesn't, it means x86_64 is doing something special we probably want. If we go with the generic approach the motivations to match OG could wait forever, my take is that, if possible, we should target for de facto approach right away.
IMO the bad experience should force the consumers to implement the OG approach, the incentives to work on the OG-like solution will diminish if we provide a working (non-optimal) path.
I believe it's important to understand the differences first. Why OG x86_64 doesn't use va_arg? I'm assuming there's a good reason for this (sorry, I don't remember anymore). I propose that after #1086 and #1087 land, you create an issue explaining (a) why the status quo isn't robuts (as your mentioned in the previous paragraph), (b) whether/how that can be fixed and (c) re-evaluate whether we should just use va_arg in face of that and what are the steps to move away from it once someone is willing to do the work. The discussion in (c) should help us decide if we should use va_arg for x86_64. How does this sound? |
Sounds good to me. And I'd like to write something down here when I have the context : )
Yeah, understanding the underlying problem is great. And I searched https://discourse.llvm.org/t/rfc-the-future-of-the-va-arg-instruction/45908 it mentions:
While these things,
To make this robust, we need a full X86_64 type classification. And also we need to be able to generate different vector types. And I also want to mark that, |
|
Thanks for pointing me to that discussion again :)
This kinda confirms that we are probably better off not using
My understanding is that this can be done without any fundamental problem in CIR -> CIR, given we add all the bits. Trying to summarize the discussion: are you saying that we should use |
Yes in the end of the day. And in fact, the design of clangir allows us to get rid of va_arg completely. As it is mentioned in the above thread:
Frontend are too early and SelectionDAG are too late then clangir looks in the proper position : )
Yes. And I feel |
bcardosolopes
pushed a commit
that referenced
this pull request
Nov 13, 2024
This is the following of #1100. After #1100, when we want to use LongDouble for VAArg, we will be in trouble due to details in X86_64's ABI and this patch tries to address this. The practical impact the patch is, after this patch, with #1088 and a small following up fix, we can build and run all C's benchmark in SpecCPU 2017. I think it is a milestone.
smeenai
force-pushed
the
main
branch
2 times, most recently
from
4aca8d4
to
a04cf10
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I tried to reopen #865 but github get stucked..
After one month's deep experience with this patch, now I am more confident we need this patch.
For the long term, in the end of the day, we will need this since
va_arginstruction is used in other targets in the traditional CodeGen pipeline. And in fact, theva_arginstruction lowering the default one in the traditional CG pipeline.For the short term, this is still needed given we have non-robust X86 arguments classification today (See #1087). VAArg is pretty common in C codes. Without this, people who want to try clangir in the early days will meet the failures, this is pretty a bad experience.
For the maintaining concerns, since now we have #1086, we can add support more types after we make X86's arguments classification more stable. Like we did in #1087.
And it shows the code generated with
va_argis pretty good and LLVM will emit the error immediately if the LLVM can't handle it well.