Missing function attributes and data layout information

[DominikAdamski]

Hi,
I noticed that we miss target triple and function attributes when we lower C code to Clang IR and then LLVM IR. Do you know how can I preserve this information?

Example:
C code:
int foo() { return 0; }
When I run command clang -S -emit-llvm test.c -o - I got the following LLVM IR:

source_filename = "test.c"
target datalayout = "e-m:e-p270:32:32-p(...)"
target triple = "x86_64-unknown-linux-gnu"
define dso_local i32 @foo() #0 {
entry:
   ret i32 0
}
attributes #0 = { noinline nounwind optnone uwtable "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse, +sse2,+x87" "tune-cpu"="generic" }

When I run mlir code gen, then I miss information about function attributes and target triple:
bin/clang -fclangir-enable t.c -emit-cir -o - | bin/cir-tool -cir-to-llvm -o - | bin/mlir-translate -mlir-to-llvmir -o -
Output is as follows:

source_filename = "LLVMDialectModule"
;No target triple information
define i32 @foo() {
;some LLMV IR instructions
}
;no function attributes for foo function

[bcardosolopes]

Hello @DominikAdamski. Yes, it's a known issue we're still missing the emission of those, we'll get there at some point - patches are welcome in the meantime :)

[DominikAdamski]

Hi @bcardosolopes,
Thank you for quick response. Function attributes are required not only for pure C code, but also for OpenMP offloading calculations into another target (for example GPU). OpenMP dialect is already part of the llvm-project but it does not support target offloading.

There is a RFC where we are wondering how to implement function attributes. Could you share your point of view about function attributes for OpenMP ( https://discourse.llvm.org/t/rfc-omp-module-and-omp-function-vs-dialect-attributes-to-encode-openmp-properties/67998 ) ? I am sure that proper implementation of function attributes will be beneficial both for CIR and OpenMP folks.

[bcardosolopes]

• Function attributes: attributes could be added either as part of first class cir.func attributes or via the generic extra ones.
• Datalayout: implemented using the MLIR provided dialect, supported for all types we define.