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Diffstat (limited to 'llvm/docs')
| -rw-r--r-- | llvm/docs/LangRef.rst | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index b1a92dc0ebd..cafc208ba8d 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -1509,6 +1509,46 @@ operand bundles do not capture their operands except during deoptimization, in which case control will not be returned to the compiled frame. +The inliner knows how to inline through calls that have deoptimization +operand bundles. Just like inlining through a normal call site +involves composing the normal and exceptional continuations, inlining +through a call site with a deoptimization operand bundle needs to +appropriately compose the "safe" deoptimization continuation. The +inliner does this by prepending the parent's deoptimization +continuation to every deoptimization continuation in the inlined body. +E.g. inlining ``@f`` into ``@g`` in the following example + +.. code-block:: llvm + + define void @f() { + call void @x() ;; no deopt state + call void @y() [ "deopt"(i32 10) ] + call void @y() [ "deopt"(i32 10), "unknown"(i8* null) ] + ret void + } + + define void @g() { + call void @f() [ "deopt"(i32 20) ] + ret void + } + +will result in + +.. code-block:: llvm + + define void @g() { + call void @x() ;; still no deopt state + call void @y() [ "deopt"(i32 20, i32 10) ] + call void @y() [ "deopt"(i32 20, i32 10), "unknown"(i8* null) ] + ret void + } + +It is the frontend's responsibility to structure or encode the +deoptimization state in a way that syntactically prepending the +caller's deoptimization state to the callee's deoptimization state is +semantically equivalent to composing the caller's deoptimization +continuation after the callee's deoptimization continuation. + .. _moduleasm: Module-Level Inline Assembly |
