[LLVMdev] Help with error in pass
Fernando Magno Quintao Pereira
fernando at CS.UCLA.EDU
Sat Jun 24 12:31:01 PDT 2006
Dear LLVM guys,
I've solved my problem with the passes, and compiled my first code
using the new register allocator! Debugging was quite easy, using gdb.
The problem was that I was forgetting to initialize the array that records
the physical registers ever used (MachineFunction::UsedPhysRegs). This is
a very minor thing, but I would suggest asserting that the vector has
been initialized before it is used in functions such as
runOnMachineFunction::X86FloatingPoint.cpp or
PPCRegisterInfo::emitPrologue.
Now I have another question. My register allocator is generating code
like this:
.text
.align 16
.globl main
main:
subl $2, %esp
fnstcw (%esp)
movb $2, 1(%esp)
fldcw (%esp)
xorl %eax, %eax
movl %eax, %eax <----------------------
addl $2, %esp
ret
.size main, .-main
Whereas RegAllocLocal.cpp is producing this one here:
.text
.align 16
.globl main
main:
subl $2, %esp
fnstcw (%esp)
movb $2, 1(%esp)
fldcw (%esp)
xorl %eax, %eax
addl $2, %esp
ret
.size main, .-main
Is it the "Two-Address instruction pass" that is removing that move marked
above?
Thanks a lot,
Fernando
> On Fri, 23 Jun 2006, Fernando Magno Quintao Pereira wrote:
> > I am getting an error with my pass implementation, and I cannot figure
> > it out. Basically, I've implemented part of a register allocation
> > algorithm, but I am having problems to set the passes correctly. For
> > instance, for this program below, the following error message is
> > produced:
>
> It's hard to say without more details, i.e. a stack trace in gdb. What
> pass is it crashing in, for example?
>
> -Chris
>
> > .c ----------------------| .bc ---------------------------------
> > | Live Outs: EAX
> > |
> > #include <stdio.h> | entry (0x8d4c6c0, LLVM BB @0x8d46970):
> > | FNSTCW16m <fi#0>, 1, %NOREG, 0
> > int main() { | MOV8mi <fi#0>, 1, %NOREG, 1, 2
> > return 0; | FLDCW16m <fi#0>, 1, %NOREG, 0
> > } | %reg1024 = MOV32r0
> > | %EAX = MOV32rr %reg1024
> > | RET
> >
> > llc((anonymous namespace)::PrintStackTrace()+0x18)[0x88cfa30]
> > llc((anonymous namespace)::SignalHandler(int)+0x107)[0x88cfcc1]
> > /lib/tls/libc.so.6[0x239f48]
> > llc(llvm::MachineFunctionPass::runOnFunction(llvm::Function&)+0x28)[0x8400638]
> > llc(llvm::FunctionPassManagerT::runPass(llvm::FunctionPass*,
> > llvm::Function*)+0x1b)[0x8857349]
> > llc(llvm::PassManagerT<llvm::FTraits>::runPasses(llvm::Function*,
> > std::map<llvm::Pass*, std::vector<llvm::Pass*, std::allocator<llvm::Pass*>
> >> , std::less<llvm::Pass*>, std::allocator<std::pair<llvm::Pass* const,
> > std::vector<llvm::Pass*, std::allocator<llvm::Pass*> > > >
> >> &)+0x11c)[0x8858bca]
> > llc(llvm::PassManagerT<llvm::FTraits>::runOnUnit(llvm::Function*)+0x16f)[0x885865f]
> > llc(llvm::FunctionPassManagerT::runOnFunction(llvm::Function&)+0x22)[0x8858e84]
> > llc(llvm::FunctionPass::runOnModule(llvm::Module&)+0xa6)[0x8854bd2]
> > llc(llvm::ModulePassManager::runPass(llvm::ModulePass*,
> > llvm::Module*)+0x1b)[0x8857541]
> > llc(llvm::PassManagerT<llvm::MTraits>::runPasses(llvm::Module*,
> > std::map<llvm::Pass*, std::vector<llvm::Pass*, std::allocator<llvm::Pass*>
> >> , std::less<llvm::Pass*>, std::allocator<std::pair<llvm::Pass* const,
> > std::vector<llvm::Pass*, std::allocator<llvm::Pass*> > > >
> >> &)+0x11c)[0x88596cc]
> > llc(llvm::PassManagerT<llvm::MTraits>::runOnUnit(llvm::Module*)+0x16f)[0x8859161]
> > llc(llvm::ModulePassManager::runOnModule(llvm::Module&)+0x22)[0x8853bea]
> > llc(llvm::PassManager::run(llvm::Module&)+0x1f)[0x8853f81]
> > llc(main+0xee2)[0x83d36ea]
> > /lib/tls/libc.so.6(__libc_start_main+0xe4)[0x227ad4]
> > llc[0x83d2779]
> > Segmentation fault (core dumped)
> > ------------------------------------------------------------------------------
> >
> > My allocator is assigning EAX to %reg1024, and this is exactly what any of
> > the LLVM built-in allocators do. The list of passes that I am invoking is
> > as follows:
> >
> > Pass Arguments: -verify -loopsimplify -loop-reduce -lowergc -lowerinvoke
> > -unreachableblockelim
> > Target Data Layout
> > Debug Information
> > Module Pass Manager
> > Function Pass Manager
> > Immediate Dominators Construction
> > ET Forest Construction
> > Module Verifier
> > -- Module Verifier
> > Natural Loop Construction
> > Dominator Set Construction
> > Dominator Tree Construction
> > -- Immediate Dominators Construction
> > Canonicalize natural loops
> > -- Dominator Set Construction
> > -- Dominator Tree Construction
> > Scalar Evolution Analysis
> > Loop Strength Reduction
> > -- ET Forest Construction
> > -- Scalar Evolution Analysis
> > -- Canonicalize natural loops
> > -- Loop Strength Reduction
> > -- Natural Loop Construction
> > Lower GC intrinsics, for GCless code generators
> > -- Lower GC intrinsics, for GCless code generators
> > Lower invoke and unwind, for unwindless code generators
> > -- Lower invoke and unwind, for unwindless code generators
> > Remove unreachable blocks from the CFG
> > -- Remove unreachable blocks from the CFG
> > X86 DAG->DAG Instruction Selection
> > -- X86 DAG->DAG Instruction Selection
> > **************** Due to my register allocator *******************
> > Immediate Dominators Construction
> > ET Forest Construction
> > -- Immediate Dominators Construction
> > Natural Loop Construction
> > -- ET Forest Construction
> > Virtual to def/use mapping - Fernando.
> > -- Natural Loop Construction
> > Edge liveness analyses - Fernando.
> > Register allocation via coloring of chordal graphs.
> > -- Register allocation via coloring of chordal graphs.
> > -- Virtual to def/use mapping - Fernando.
> > -- Edge liveness analyses - Fernando.
> > *****************************************************************
> > Live Variable Analysis
> > X86 FP Stackifier
> > -- X86 FP Stackifier
> > -- Live Variable Analysis
> > Prolog/Epilog Insertion & Frame Finalization
> > -- Prolog/Epilog Insertion & Frame Finalization
> > X86 AT&T-Style Assembly Printer
> > -- X86 AT&T-Style Assembly Printer
> > Machine Code Deleter
> > -- Machine Code Deleter
> >
> > Could some one tell me what is(are) the most likely reason(s) for this
> > error? I would really appreciate any help,
> >
> > Thanks a lot,
> >
> > Fernando
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>
> -Chris
>
> --
> http://nondot.org/sabre/
> http://llvm.org/
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