similar to: [LLVMdev] fastcc, tail calls, and gcc

On Thu, Feb 12, 2009 at 5:34 PM, Jeff Kuskin <jk500500 at yahoo.com> wrote: > Two related questions. > (2) Why does the x86-64 JIT backend generate a "ret $0x8" instruction > to return from a fastcc function that is (a) marked as fastcc > (CallingConv::Fast); but (b) takes no arguments and returns 'void'? fastcc generated code ends with this: > c20800

Jeff Kuskin wrote: > Correct? If not, how do I call a LLVM JIT-generated fastcc function > from a function statically compiled by GCC? Well, you can always generate a little wrapper function with C calling convention which just calls the fastcc function. -- Dr. Albert Gr"af Dept. of Music-Informatics, University of Mainz, Germany Email: Dr.Graef at t-online.de, ag at

Albert Graef wrote: > Jeff Kuskin wrote: >> Correct? If not, how do I call a LLVM JIT-generated fastcc function >> from a function statically compiled by GCC? > > Well, you can always generate a little wrapper function with C calling > convention which just calls the fastcc function. > I use the fastcall convention all the time. LLVM-jitted code calling GCC-compile

On Oct 5, 2007, at 2:42 AM, Arnold Schwaighofer wrote: > Hi Evan, > I incoporated the changes you request but to the following i have got > a question: > >> Also, moving the option >> there will allow us to change fastcc ABI (callee popping arguments) >> only when this option is on. See Chris' email: > > I am not to sure on that. because that would make

Hi Evan, I incoporated the changes you request but to the following i have got a question: > Also, moving the option > there will allow us to change fastcc ABI (callee popping arguments) > only when this option is on. See Chris' email: I am not to sure on that. because that would make modules compiled with the flag on incompatible with ones compiled without the flag off as

On Feb 12, 2009, at 3:23 PM, Albert Graef wrote: > Jeff Kuskin wrote: >> Correct? If not, how do I call a LLVM JIT-generated fastcc function >> from a function statically compiled by GCC? > > Well, you can always generate a little wrapper function with C calling > convention which just calls the fastcc function. You can do a quick bit of assembly code to make sure that

On 24 Sep 2007, at 09:18, Evan Cheng wrote: > +; RUN: llvm-as < %s | llc -march=x86 -mattr=+sse2 -stats -info- > output-file - | grep asm-printer | grep 9 > +; change preceeding line form ... | grep 8 to ..| grep 9 since > +; with new fastcc has std call semantics causing a stack adjustment > +; after the function call > > Not sure if I understand this. Can you illustrate

For marking a call site as a tail call you have to call void setTailCall(bool isTC = true) on the CallInst. The calling convention of the function needs to be CallingConv::Fast (currently only fastcc calls are optimized) and the call has to be in tail position of course. To enable tail call optimization in an embedded vm i guess you would include llvm/Target/TargetOptions.h and set the static

On Sep 24, 2007, at 2:25 AM, Arnold Schwaighofer wrote: > > On 24 Sep 2007, at 09:18, Evan Cheng wrote: >> +; RUN: llvm-as < %s | llc -march=x86 -mattr=+sse2 -stats -info- >> output-file - | grep asm-printer | grep 9 >> +; change preceeding line form ... | grep 8 to ..| grep 9 since >> +; with new fastcc has std call semantics causing a stack adjustment >>

> > FastCC use to be caller pops arguments so there was no stack > > adjustment after the > > call to qux. Now FastCC has callee pops arguments on return semantics > > so the > > x86 backend inserts a stack adjustment after the call. > > > > _array: > > subl $12, %esp > > movss LCPI1_0, %xmm0 > > mulss

Comments: CheckDAGForTailCallsAndFixThem - 1. for (SelectionDAG::allnodes_iterator BE = DAG.allnodes_begin(), + BI = prior(DAG.allnodes_end()); BI != BE; BI--) { Please use pre-decrement instead of post-decrement. 2. The function is slower than it should be. You are scanning all the nodes in the DAG twice. You should just examine DAG.getRoot() to make determine whether it's a

On Oct 5, 2007, at 10:41 AM, Evan Cheng wrote: > > On Oct 5, 2007, at 2:42 AM, Arnold Schwaighofer wrote: > >> Hi Evan, >> I incoporated the changes you request but to the following i have got >> a question: >> >>> Also, moving the option >>> there will allow us to change fastcc ABI (callee popping arguments) >>> only when this option is

Hi Arnold, This is a very good first step! Thanks! Comments below. Evan Index: test/CodeGen/X86/constant-pool-remat-0.ll =================================================================== --- test/CodeGen/X86/constant-pool-remat-0.ll (revision 42247) +++ test/CodeGen/X86/constant-pool-remat-0.ll (working copy) @@ -1,8 +1,10 @@ ; RUN: llvm-as < %s | llc -march=x86-64 | grep LCPI | count 3 ;

Okay so i implemented an(other :) initial version for X86-32 backend, this time based on TOT: It is not very generic at the moment. Only functions with callingconv::fastcc and the tail call attribute will be optimized. Maybe the next step should be to integrate the code into the other calling convention lowering. Here is what i have at the moment: If callingconv::fastcc is used the

Hi Arnold and Anton, Sorry I have been ignoring your emails on this topic. It's an important task and I really need sometime to think about it (and talk to Chris about it!) But this has been an especially hectic week. I am also going to vacation soon so I am not sure when I would get around to it. If Chris has time, I am sure he has lots to say on this topic. :-) Otherwise, please

Hello, Arnold. Only quick comments, I'll try to make a full review a little bit later. > 0.)a fast calling convention (maybe use the current > CallingConv::Fast, or create a CallingConv::TailCall) > 1.) lowering of formal arguments > like for example x86_LowerCCCArguments in stdcall mode > we need to make sure that later mentioned CALL_CLOBBERED_REG is >

Hi Evan, first off thanks to you and Chris for taking time. On 6 Sep 2007, at 00:57, Evan Cheng wrote: > We'd like to see tail call optimization to be similar to the target > independent lowering of ISD::CALL nodes. These are auto-generated > from ???CallingConv.td files. Some target specific details such as > function address register (ECX in your example) should be coded in

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On Fri, 5 Oct 2007, Arnold Schwaighofer wrote: >> to me like llvm-gcc honors that. Certainly it should. > > This would imply one fastcc abi (callee pops args on return) to rule > them all? > That is only if fastcall translates to llvm fastcc of course. fastcall != fastcc. fastcall is a well defined convention on x86 that has very specific ABI requirements. fastcc, on the

On 5 Oct 2007, at 20:00, Dale Johannesen wrote: >>> I am not to sure on that. because that would make modules compiled >>> with the flag on incompatible with ones compiled without the flag >>> off >>> as stack behaviour would mismatch. >>> It would be no problem to make the behaviour dependent on the -tail- >>> call-opt flag. i am not sure