Izaron marked an inline comment as done.
Izaron added a comment.
In D144334#4142490 <https://reviews.llvm.org/D144334#4142490>, @erichkeane
wrote:
> Just deliberately not support a part of C++2b. Implementers have veto'ed
> features in the past exactly that way.
That's sad. Let's at least write some warning on the `cxx_status.html` like "we
aren't gonna implement it".
================
Comment at: clang/lib/CodeGen/CGStmt.cpp:723-727
+ case attr::Assume: {
+ llvm::Value *ArgValue = EmitScalarExpr(cast<AssumeAttr>(A)->getCond());
+ llvm::Function *FnAssume = CGM.getIntrinsic(llvm::Intrinsic::assume);
+ Builder.CreateCall(FnAssume, ArgValue);
+ break;
----------------
cor3ntin wrote:
> I'm not familiar with codegen. what makes the expression non-evaluated here?
The LLVM docs says it: https://llvm.org/docs/LangRef.html#llvm-assume-intrinsic
> No code is generated for this intrinsic, and instructions that contribute
> only to the provided condition are not used for code generation
The `ArgValue` and `FnAssume` are the instructions to be discarded according to
this sentence.
I guess they do it via dead code elimination (at any optimization level).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D144334/new/
https://reviews.llvm.org/D144334
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