[LLVMdev] Seeing a crash with ConstantFP::get

[Chuck Rose III]

Hola Dale,

 

I spent some time walking through what's going on with a friend of mine
from VStudio.  Category is given 2 bits in the APFloat class definition.
It's sign extending the enum value for the comparisons when it loads it
out of the class, so the 2 becomes a -2 and the comparison fails.  He
sent me a piece of code which I might be able to use to force the issue.
I'll update when I try that out. 

 

Thanks,

Chuck.

 

________________________________

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
On Behalf Of Chuck Rose III
Sent: Wednesday, September 05, 2007 2:51 PM
To: LLVM Developers Mailing List
Subject: Re: [LLVMdev] Seeing a crash with ConstantFP::get

 

It's in debug.  I'm having a look at the assembler it's producing right
now and it's definitely a little odd for what should be a simple
assignment in zeroSignificand. 

 

________________________________

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
On Behalf Of Dale Johannesen
Sent: Wednesday, September 05, 2007 2:39 PM
To: LLVM Developers Mailing List
Subject: Re: [LLVMdev] Seeing a crash with ConstantFP::get

 

 

On Sep 5, 2007, at 2:21 PM, Chuck Rose III wrote:

 

Hola LLVMers,

 

I'm getting a crash when using ConstantFP::get.

 

I can repro it by adding one line to the Fibonacci example program:

 

int main(int argc, char **argv) {

  int n = argc > 1 ? atol(argv[1]) : 24;

 

  // Create some module to put our function into it.

  Module *M = new Module("test");

 

  // We are about to create the "fib" function:

  Function *FibF = CreateFibFunction(M);

 

// add the following line

  Constant* C = ConstantFP::get(Type::FloatTy,0.0);

 

 

Can someone verify this?  This is on the PC side of my system which I
build with the VStudio files.  I don't know if the Mac side sees this as
well, but I'll try and verify.  Seems really odd to have something this
basic crash me.  It came up because the JITter will call ConstantFP::get
with the GenericValue arguments passed it, but the above repro is a lot
simpler and is independent of the JITter.

 

My call stack looks like this:

 

            in here it fails this:  assert(category == fcNormal ||
category == fcNaN);

            Fibonacci.exe!llvm::APFloat::significandParts()  Line 360 +
0x39 bytes    C++

            Fibonacci.exe!llvm::APFloat::zeroSignificand()  Line 387 +
0x15 bytes     C++

I've been working in this area and probably introduced this, but I don't
see how:  zeroSignificand() sets 'category' to fcNormal before calling
significandParts, so I don't see how that assert could be triggered.
The call stack looks normal for that source line.  It doesn't appear on
the Mac.   Could your compiler be misoptimizing the code?

	            Fibonacci.exe!llvm::APFloat::APFloat(const
llvm::fltSemantics & ourSemantics={...}, unsigned __int64 value=1)  Line
307       C++

	            Fibonacci.exe!`anonymous
namespace'::DenseMapAPFloatKeyInfo::getEmptyKey()  Line 277 + 0x11 bytes
C++

	            Fibonacci.exe!llvm::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo>::getEmptyKey()  Line 236 + 0x9
bytes          C++

	            Fibonacci.exe!llvm::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo>::init(unsigned int
InitBuckets=64)  Line 295 + 0x9 bytes         C++

	            Fibonacci.exe!llvm::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo>::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo>(unsigned int NumInitBuckets=64)
Line 68      C++

	
Fibonacci.exe!llvm::ManagedStatic<llvm::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo> >::LazyInit()  Line 72 + 0x24
bytes     C++

	
Fibonacci.exe!llvm::ManagedStatic<llvm::DenseMap<`anonymous
namespace'::DenseMapAPFloatKeyInfo::KeyTy,llvm::ConstantFP
*,A0x5b1fa632::DenseMapAPFloatKeyInfo> >::operator*()  Line 55  C++

	            Fibonacci.exe!llvm::ConstantFP::get(const llvm::Type
* Ty=0x01b352d8, double V=0.00000000000000000)  Line 299 + 0xe bytes
C++

	            Fibonacci.exe!main(int argc=1, char * *
argv=0x01b35060)  Line 99 + 0x13 bytes  C++

	            Fibonacci.exe!__tmainCRTStartup()  Line 586 + 0x19
bytes         C

	            Fibonacci.exe!mainCRTStartup()  Line 403          C

	 

	Thanks,

	Chuck.

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