Re: [PATCH] sparse, llvm: Fix 'void' return type code generation

[Jeff Garzik <jgarzik@pobox.com>]

On 08/19/2012 05:28 AM, Pekka Enberg wrote:
> Jonathan Neuschäfer reports:
>
>    A simple function like this will compile to the following llvm
>    bitcode:
>
>          /* C */
>          void func(void) {
>                  return;
>          }
>
>          /* LLVM */
>          define i8 @func() {
>          L0:
>            ret void
>          }
>
>    The return type of the function and the type in the return instruction
>    don't match.
>
>    I found this inconsistency by running LLVM's bitcode validation on the
>    bitcode produced by sparse-llvm.
>
> Move 'void *' special-casing from sym_basetype_type() to sym_ptr_type()
> to fix the issue.
>
> Reported by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> Cc: Christopher Li <sparse@chrisli.org>
> Cc: Jeff Garzik <jgarzik@redhat.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Pekka Enberg <penberg@kernel.org>
> ---
>   sparse-llvm.c                         |   12 ++++++++++--
>   validation/backend/void-return-type.c |   13 +++++++++++++
>   2 files changed, 23 insertions(+), 2 deletions(-)
>   create mode 100644 validation/backend/void-return-type.c
>
> diff --git a/sparse-llvm.c b/sparse-llvm.c
> index e02e212..213d42d 100644
> --- a/sparse-llvm.c
> +++ b/sparse-llvm.c
> @@ -150,7 +150,13 @@ static LLVMTypeRef sym_union_type(LLVMModuleRef module, struct symbol *sym)
>
>   static LLVMTypeRef sym_ptr_type(LLVMModuleRef module, struct symbol *sym)
>   {
> -	LLVMTypeRef type = symbol_type(module, sym->ctype.base_type);
> +	LLVMTypeRef type;
> +
> +	/* 'void *' is treated like 'char *' */
> +	if (is_void_type(sym->ctype.base_type))
> +		type = LLVMInt8Type();
> +	else
> +		type = symbol_type(module, sym->ctype.base_type);
>
>   	return LLVMPointerType(type, 0);
>   }
> @@ -176,10 +182,12 @@ static LLVMTypeRef sym_basetype_type(struct symbol *sym)
>   		}
>   	} else {
>   		switch (sym->bit_size) {
> +		case -1:
> +			ret = LLVMVoidType();
> +			break;
>   		case 1:
>   			ret = LLVMInt1Type();
>   			break;
> -		case -1:	/* 'void *' is treated like 'char *' */
>   		case 8:
>   			ret = LLVMInt8Type();
>   			break;
> diff --git a/validation/backend/void-return-type.c b/validation/backend/void-return-type.c
> new file mode 100644
> index 0000000..b282fde
> --- /dev/null
> +++ b/validation/backend/void-return-type.c
> @@ -0,0 +1,13 @@
> +static void foo(void)
> +{
> +}
> +
> +static void *bar(void *p)
> +{
> +	return p;
> +}
> +

ACK the code...  would prefer that the first testcase included a 
"return;" just to be certain we get that right.

	Jeff




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