llvm dev - Dec 2012 - [LLVMdev] alignment issue, getting corrupt double values

I'm having an issue where a certain set of types and insert/extractvalue
are producing the incorrect values. It appears as though extractvalue
getting my sub-structure is not getting the correct data.

I have these types:

%outer = type { i32, %inner, i1 }
%inner = type { double, i32 }

The trouble is that when I have a value of type %outer then proceed to
extract the components of the contained %inner structure I get corrupt
values. If I don't have the "i1" type in there everything works
fine,
leading me to think it is something to do with alignment. I do the
extraction with code like this:

	%o = call %outer @eval_expr()
	%s = extractvalue %outer %o, 1
	%s1 = extractvalue %inner %s, 0

The %s1 value is not correct (not what was inserted). I think extraction
is the problem and not insertion: in another version I store the value
to a global variable and dump the bytes of the structure, which can then
be properly extracted in C++ code.  The value is produced with this code
(in a separate function):

	%s0 = insertvalue %inner undef, double 1.500000e+00, 0
	%s1 = insertvalue %inner %s0, i32 2, 1
	%s2 = insertvalue %outer undef, i32 1, 0
	%s3 = insertvalue %outer %s2, %inner %s1, 1


I've attached the full sample code which shows the error and where it
happens.

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; /opt/llvm/install/bin/llc types.ll -o types.s && clang -o foo types.s
&& ./foo
%outer = type { i32, %inner, i1 } ; REMOVE the i1 and it works
%inner = type { double, i32 }

define %outer @eval_expr() {
entry:
	%s0 = insertvalue %inner undef, double 1.500000e+00, 0
	%s1 = insertvalue %inner %s0, i32 2, 1
	%s2 = insertvalue %outer undef, i32 1, 0
	%s3 = insertvalue %outer %s2, %inner %s1, 1
	;%s4 = insertvalue %outer %s3, i1 false, 2
	ret %outer %s3
}

define void @main() {
entry:
	%o = call %outer @eval_expr()
	%s = extractvalue %outer %o, 1
	%s1 = extractvalue %inner %s, 0 ;ERROR: this value is 0.0, expected 1.5
	call void @trace_float(double %s1)
	%s2 = extractvalue %inner %s, 1 ;ERROR: this value is 1073217536, expected 2
	call void @trace_integer(i32 %s2)
	ret void
}

; simple tracing functions
@.int_str = private unnamed_addr constant [4 x i8] c"%d\0A\00"
define void @trace_integer( i32 %i ) {
entry:
	%sp = getelementptr [4 x i8]* @.int_str, i32 0, i32 0
	call i32 (i8*, ...)* @printf(i8* %sp, i32 %i)
	ret void
}

@.float_str = private unnamed_addr constant [4 x i8] c"%f\0A\00"
define void @trace_float( double %i ) {
entry:
	%sp = getelementptr [4 x i8]* @.float_str, i32 0, i32 0
	call i32 (i8*, ...)* @printf(i8* %sp, double %i)
	ret void
}

declare i32 @printf(i8*, ...)
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I also saw this issue before.  Llvm seems have trouble returning general
struct values from functions.  One easy workaround is to use packed struct
type.

Hope this helps.

-Peng

On Sunday, December 30, 2012, edA-qa mort-ora-y wrote:
> I'm having an issue where a certain set of types and
insert/extractvalue
> are producing the incorrect values. It appears as though extractvalue
> getting my sub-structure is not getting the correct data.
>
> I have these types:
>
> %outer = type { i32, %inner, i1 }
> %inner = type { double, i32 }
>
> The trouble is that when I have a value of type %outer then proceed to
> extract the components of the contained %inner structure I get corrupt
> values. If I don't have the "i1" type in there everything
works fine,
> leading me to think it is something to do with alignment. I do the
> extraction with code like this:
>
>         %o = call %outer @eval_expr()
>         %s = extractvalue %outer %o, 1
>         %s1 = extractvalue %inner %s, 0
>
> The %s1 value is not correct (not what was inserted). I think extraction
> is the problem and not insertion: in another version I store the value
> to a global variable and dump the bytes of the structure, which can then
> be properly extracted in C++ code.  The value is produced with this code
> (in a separate function):
>
>         %s0 = insertvalue %inner undef, double 1.500000e+00, 0
>         %s1 = insertvalue %inner %s0, i32 2, 1
>         %s2 = insertvalue %outer undef, i32 1, 0
>         %s3 = insertvalue %outer %s2, %inner %s1, 1
>
>
> I've attached the full sample code which shows the error and where it
> happens.
>
> --
> edA-qa mort-ora-y
> -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> Sign: Please digitally sign your emails.
> Encrypt: I'm also happy to receive encrypted mail.
>
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I can confirm that if I generate the value directly (not via a return)
then the expected values are extracted from the structure. So it is
perhaps a return value issue.

On 30/12/12 19:04, Peng Cheng wrote:
> I also saw this issue before.  Llvm seems have trouble returning general
> struct values from functions.  One easy workaround is to use packed
> struct type.
> 
> Hope this helps.
> 
> -Peng
> 
> On Sunday, December 30, 2012, edA-qa mort-ora-y wrote:
> 
>     I'm having an issue where a certain set of types and
insert/extractvalue
>     are producing the incorrect values. It appears as though extractvalue
>     getting my sub-structure is not getting the correct data.
> 
>     I have these types:
> 
>     %outer = type { i32, %inner, i1 }
>     %inner = type { double, i32 }
> 
>     The trouble is that when I have a value of type %outer then proceed to
>     extract the components of the contained %inner structure I get corrupt
>     values. If I don't have the "i1" type in there everything
works fine,
>     leading me to think it is something to do with alignment. I do the
>     extraction with code like this:
> 
>             %o = call %outer @eval_expr()
>             %s = extractvalue %outer %o, 1
>             %s1 = extractvalue %inner %s, 0
> 
>     The %s1 value is not correct (not what was inserted). I think
extraction
>     is the problem and not insertion: in another version I store the value
>     to a global variable and dump the bytes of the structure, which can
then
>     be properly extracted in C++ code.  The value is produced with this
code
>     (in a separate function):
> 
>             %s0 = insertvalue %inner undef, double 1.500000e+00, 0
>             %s1 = insertvalue %inner %s0, i32 2, 1
>             %s2 = insertvalue %outer undef, i32 1, 0
>             %s3 = insertvalue %outer %s2, %inner %s1, 1
> 
> 
>     I've attached the full sample code which shows the error and where
it
>     happens.
> 
>     --
>     edA-qa mort-ora-y
>     -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
>     Sign: Please digitally sign your emails.
>     Encrypt: I'm also happy to receive encrypted mail.
> 

-- 
edA-qa mort-ora-y
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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