On Mon, Mar 6, 2017 at 8:43 AM, Luc Van Oostenryck
<luc.vanoostenryck@xxxxxxxxx> wrote:
>
> With an example:
> == C code ==
> void *foo(int *p) { return p + 5; }
>
> == linearized code ==
> foo:
> .L0:
> <entry-point>
> add.64 %r2 <- %arg1, $20
> cast.64 %r3 <- (64) %r2
> ret.64 %r3
This is correct.
> == LLVM code from sparse-llvm ==
>
> define i8* @foo(i32* %ARG1) {
> L0:
> %0 = getelementptr i32, i32* %ARG1, inttoptr (i64 20 to i32*)
> %R3 = bitcast i32* %0 to i8*
This is garbage, I'm afraid.
When sparse does the "add 20 to pointer", it adds the *byte offset* 20
to the pointer. The LLVM module should not use "getelementptr" for
this, because it's not element #20, it's the element at offset 20.
I think you're supposed to either use "uglygep" with the base pointer
cast to a simple address-unit pointer (ie unsigned char).
Or not use GEP at all.
Linus
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