global register variables not supported

[llvmbot]

Bugzilla Link	2522
Resolution	WORKSFORME
Resolved on	May 04, 2012 06:41
Version	2.3
OS	Windows XP
Blocks	llvm/llvm-bugzilla-archive#4068
Reporter	LLVM Bugzilla Contributor
CC	@asl,@edwintorok

Extended Description

While attempting to compile a C file generated by GHC. llvm-gcc chocked with the error message "sorry, unimplemented: LLVM cannot register variable 'R1'." and requested I report a bug.

The GHC version was ghc-6.8.3.

From the root of the GHC installation the path to the header llvm-gcc was parsing is "include/Regs.h" and the error occured at line 220.

David

[asl]

Please attach reproducible testcase

[lattner]

GHC probably depends on the GNU extension to pin global variables to physregs. This is not fully supported by llvm-gcc at this time. Please do include a testcase though.

[llvmbot]

haskell source and makefile to repeat issue
llvm-gcc output does say the feature is not implemented. It also requests I submit a bug report which is why I have.

I checked this out a little further today, and GHC does allow me to work around the register issue by defining 'NO_REGS'.

[llvmbot]

Forgot to mention. The makefile requires a variable.

'GHC_HOME=path/to/ghc-6.8.3/installation'

[asl]

Preprocessed .c source
Please next time include .c source, not haskell :)

[lattner]

This is basically:

register StgUnion R1 asm("%" "esi");

where StgUnion is a big and scary thing. Putting a union in a register is vaguely wierd, but I can see why you'd want to do it. :)

[edwintorok]

This is also an issue if you try to build a 32-bit Linux kernel (ARCH=i386):
/home/edwin/builds/linux-2.6/arch/x86/include/asm/thread_info.h:179:24: error: global register variables are not supported
register unsigned long current_stack_pointer asm("esp") __used;
^

[llvmbot]

Edwin's example works for me with dragonegg. The preprocessed source for the
original example is rejected by recent versions of gcc.

[edwintorok]

mentioned in issue llvm/llvm-bugzilla-archive#4068