Hi Duncan,
Some nit picks.
1. Please don't use "Chain" for stand for function static chain. It
confuses backend guys like me. :-) "Chain" stands for control flow
dependency in the backend.
2. Purely a stylistic thing:
+SDOperand X86TargetLowering::LowerTRAMPOLINE(SDOperand Op,
+ SelectionDAG &DAG) {
+ SDOperand Root = Op.getOperand(0);
+ SDOperand Trmp = Op.getOperand(1); // trampoline
+ SDOperand FPtr = Op.getOperand(2); // nested function
+ SDOperand SChn = Op.getOperand(3); // static chain
+
+ SrcValueSDNode *TrmpSV = cast<SrcValueSDNode>(Op.getOperand(4));
+
+ if (Subtarget->is64Bit()) {
+ return SDOperand(); // not yet supported
+ } else {
If you move the check is64Bit() to the beginning of function, there
is no need to nest the part that actually do the work in the "else"
clause.
3. In X86TargetLowering::LowerTRAMPOLINE():
+ case CallingConv::X86_StdCall: {
+ Move = 0xb9; // Pass chain in ECX
I assume this is the ModR/M byte? Can you refactor ModRMByte() from
X86CodeEmitter.cpp (probably also getX86RegNum) and use that to
calculate this instead? Also, isn't the static chain register
described in X86CallingConv.td? Magic number is confusing. :-)
Looks great otherwise. Thanks!
Evan
On Jul 26, 2007, at 7:56 AM, Duncan Sands wrote:
> These patches add support for taking pointers to nested
> functions (a gcc extension). This is done by building
> and executing a small code stub on the stack, known as
> a trampoline. The LLVM part adds two new intrinsics,
> llvm.init.trampoline and llvm.adjust.trampoline. The
> adjust intrinsic is implemented for all architectures
> that are supported in gcc, while the init intrinsic is
> only implemented for X86. Furthermore, trampolines can
> interact badly with stack protection mechanisms which
> don't much like execution of code on the stack. GCC
> does various tricks to tell the OS that the trampoline
> is kosher. I didn't implement any of those tricks yet,
> because it works without them on my machine :)
>
> Enjoy!
>
> Duncan.
> <tramp.diff>
> <tramp-gcc.diff>
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