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cranelift: Remove EBB references from docs (#6235)

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* Remove ebb references from compare-llvm.md

* Remove EBB references from ir.md

* Remove EBB references from testing.md

* Fix grammar

* Clean up discussion of conditionals terminating BBs

* Remove a reference to boolean types
This commit is contained in:
Trevor Elliott
2023-04-18 16:01:45 -07:00
committed by GitHub
parent 51ed20ab4d
commit c17a3d89f7
3 changed files with 43 additions and 76 deletions
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cranelift/docs/compare-llvm.md
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@@ -125,20 +125,13 @@ the [cranelift-module](https://docs.rs/cranelift-module/) crate. It provides
facilities for working with modules, which can contain multiple functions as
well as data objects, and it links them together.
An LLVM IR function is a graph of *basic blocks*. A Cranelift IR function is a
graph of *extended basic blocks* that may contain internal branch instructions.
The main difference is that an LLVM conditional branch instruction has two
target basic blocks---a true and a false edge. A Cranelift branch instruction
only has a single target and falls through to the next instruction when its
condition is false. The Cranelift representation is closer to how machine code
works; LLVM's representation is more abstract.
LLVM uses
[phi instructions](https://llvm.org/docs/LangRef.html#phi-instruction)
in its SSA representation. Cranelift passes arguments to EBBs instead. The two
representations are equivalent, but the EBB arguments are better suited to
handle EBBs that may contain multiple branches to the same destination block
with different arguments. Passing arguments to an EBB looks a lot like passing
Both LLVM and Cranelift use a graph of *basic blocks* as their IR for functions.
However, LLVM uses
[phi instructions](https://llvm.org/docs/LangRef.html#phi-instruction) in its
SSA representation while Cranelift passes arguments to BBs instead. The two
representations are equivalent, but the BB arguments are better suited to handle
BBs that may contain multiple branches to the same destination block with
different arguments. Passing arguments to a BB looks a lot like passing
arguments to a function call, and the register allocator treats them very
similarly. Arguments are assigned to registers or stack locations.