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xo-jit: helper functions -> explicit stack frames [wip, not used]

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This commit is contained in:
Roland Conybeare 2024-06-26 13:11:22 -04:00
commit be3e62f75a
1 changed files with 172 additions and 1 deletions
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173
src/jit/MachPipeline.cpp
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@ -700,6 +700,176 @@ namespace xo {
return fn;
} /*codegen_lambda_decl*/
namespace {
/** A function type:
*
* _baseframe* (*) (_baseframe*
**/
llvm::FunctionType *
require_baseframe_unwind_llvm_type(xo::ref::brw<LlvmContext> llvm_cx,
llvm::PointerType * frameptr_llvm_type)
{
std::vector<llvm::Type *> llvm_argtype_v;
llvm_argtype_v.reserve(2);
/* 1st arg is frame pointer */
llvm_argtype_v.push_back(frameptr_llvm_type);
/* 2nd arg is an i32.
* 0 -> unwind.
* 1 -> lift to heap (someday)
*/
llvm_argtype_v.push_back
(llvm::Type::getInt32Ty(llvm_cx->llvm_cx_ref()));
/* return value is frame pointer */
llvm::Type * retval_llvm_type = frameptr_llvm_type;
auto * unwind_llvm_type = llvm::FunctionType::get(retval_llvm_type,
llvm_argtype_v,
false /*!varargs*/);
return unwind_llvm_type;
} /*require_baseframe_unwind_llvm_type*/
/** Each lambda gets its own stack frame definition.
* However all the various frame representations share the same 'baseframe'
* prefix.
*
* _baseframe:
* ^
* |
* +-------+ |
* next_frame [0] | o-------/
* +-------|
* unwind_fn [1] | o-------> frame* (*)(frame*, ctl)
* +-------+
*
* This helper function generates an llvm::Type* for a baseframe.
* It only needs to be invoked once (per LlvmContext, I guess ..)
**/
llvm::StructType *
require_baseframe_llvm_type(xo::ref::brw<LlvmContext> llvm_cx)
{
/* _baseframe: base type for a stack frame */
llvm::StructType * frame_llvm_type
= llvm::StructType::get(llvm_cx->llvm_cx_ref(),
"_baseframe");
/* _baseframe*: pointer to a stack frame */
llvm::PointerType * frameptr_llvm_type
= llvm::PointerType::getUnqual(frame_llvm_type);
/* unwind function = frame[1] */
llvm::FunctionType * unwind_llvm_type
= require_baseframe_unwind_llvm_type(llvm_cx,
frameptr_llvm_type);
/* _baseframe members */
std::vector<llvm::Type *> llvm_membertype_v;
{
llvm_membertype_v.reserve(2);
/* frame[0] = pointer to next frame */
llvm_membertype_v.push_back(frameptr_llvm_type);
/* frame[1] = unwind function */
llvm_membertype_v.push_back(unwind_llvm_type);
}
frame_llvm_type->setBody(frameptr_llvm_type /*frame[0]*/,
unwind_llvm_type /*frame[1]*/);
return frame_llvm_type;
} /*require_baseframe_llvm_type*/
/** need a supporting type for stack frame
* - so we can handle variables with non-trivial dtors
* (e.g. smart pointers)
* - so we can implement nested lexical scoping
* - so we can walk stack for exception handling
* - eventually: so we can eventually implement trampoline
*
* frame representation:
*
* ^
* |
* +-------+ |
* next_frame [0] | o-------/
* +-------|
* unwind_fn [1] | o-------> baseframe* (*)(baseframe*, ctl)
* +-------|
* arg[i] [2+i] | ... |
* +-------+
*
* invoke frame.unwind_fn to dispose of a frame
* - ctl=0 dtor. deal with smart pointers etc.
* - ctl=1 copy. lift frame into heap for lambda capture
*
* every frame is a subtype of _baseframe (ofc llvm doesn't know this).
* See baseframe_llvm_type(), baseframe_unwind_llvm_type() above
*
* editor bait: activation_record_to_llvm_type
**/
llvm::StructType *
frame_to_llvm_type(xo::ref::brw<LlvmContext> llvm_cx,
ref::brw<Lambda> lambda,
llvm::Function * lambda_llvm_fn)
{
constexpr bool c_debug_flag = true;
using xo::scope;
scope log(XO_DEBUG(c_debug_flag));
/* frame type doesn't need a name */
llvm::StructType * frame_llvm_type
= llvm::StructType::get(llvm_cx->llvm_cx_ref());
/* _baseframe */
llvm::StructType * baseframe_llvm_type
= require_baseframe_llvm_type(llvm_cx);
/* _baseframe*: pointer to a generic stack frame */
llvm::PointerType * baseframeptr_llvm_type
= llvm::PointerType::getUnqual(baseframe_llvm_type);
/* _baseframe* (*)(_baseframe*, i32) */
llvm::FunctionType * unwind_llvm_type
= require_baseframe_unwind_llvm_type(llvm_cx,
baseframeptr_llvm_type);
/* llvm_argtype_v:
* - llvm_argtype_v[0] = llvm::Type* for pointer to next_frame
* - llvm_argtype_v[1] = llvm::Type* for unwind_fn
* - llvm_argtype_v[2+i] = llvm::Type* for lambda->fn_arg(i)
*/
std::vector<llvm::Type *> llvm_argtype_v;
{
llvm_argtype_v.reserve(2 + lambda_llvm_fn->arg_size());
/* frame pointer */
llvm_argtype_v.push_back(baseframeptr_llvm_type);
/* unwind function */
llvm_argtype_v.push_back(unwind_llvm_type);
int i_arg = 0;
for (auto & arg : lambda_llvm_fn->args()) {
log && log(xtag("i_arg", i_arg),
xtag("param", std::string(arg.getName())));
llvm_argtype_v.push_back(td_to_llvm_type(llvm_cx,
lambda->fn_arg(i_arg)));
++i_arg;
}
}
frame_llvm_type->setBody(llvm_argtype_v);
return frame_llvm_type;
} /*frame_to_llvm_type*/
} /*namespace*/
llvm::Function *
MachPipeline::codegen_lambda_defn(ref::brw<Lambda> lambda,
llvm::IRBuilder<> & ir_builder)
@ -724,7 +894,6 @@ namespace xo {
return nullptr;
}
/* generate function body */
auto block = llvm::BasicBlock::Create(llvm_cx_->llvm_cx_ref(), "entry", llvm_fn);
@ -733,6 +902,8 @@ namespace xo {
/** Actual parameters will need their own activation record.
* Track its shape here.
*
* Local variables will be formal parameters to a nested lambda;
**/
this->env_stack_.push(activation_record());