Re: gs_group_1 crashing on 13beta2/s390x

Hi,

On 2020-10-15 17:12:54 -0700, Andres Freund wrote:
> On 2020-10-15 15:37:01 -0700, Andres Freund wrote:
> It's a bug that was fixed in LLVM 4, but too late to be backported to
> 3.9.
> 
> The easiest seems to be to just use a wrapper function that does the
> necessary pre-checks. Something like the below (in llvmjit_wrap.cpp).
> 
> Since the wrapper still needs to call into
> LLVMGetAttributeCountAtIndexPG, it seems easier to just use the seperate
> function name, rather than #define'ing LLVMGetAttributeCountAtIndex() to
> the PG version?
> 
> /*
>  * Like LLVM's LLVMGetAttributeCountAtIndex(), works around a bug in LLVM 3.9.
>  *
>  * In LLVM <= 3.9, LLVMGetAttributeCountAtIndex() segfaults if there are no
>  * attributes at an index (fixed in LLVM commit ce9bb1097dc2).
>  */
> unsigned
> LLVMGetAttributeCountAtIndexPG(LLVMValueRef F, uint32 Idx)
> {
> 	/*
> 	 * This is more expensive, so only do when using a problematic LLVM
> 	 * version.
> 	 */
> #if LLVM_VERSION_MAJOR < 4
> 	if (!llvm::unwrap<llvm::Function>(F)->getAttributes().hasAttributes(Idx))
> 		return 0;
> #endif
> 
> 	/*
> 	 * There is no nice public API to determine the count nicely, so just
> 	 * always fall back to LLVM's C API.
> 	 */
> 	return LLVMGetAttributeCountAtIndex(F, Idx);
> }

Seems to have calmed the buildfarm, without negative consequences so far.

Greetings,

Andres Freund