On Jun 9, 2012, at 7:00 AM, Pekka Enberg wrote:
>
> Right. Looking at your "splay" backend
>
> static value_t emit_gep(builder_t builder, struct pseudo *src,
> unsigned int offset, struct pseudo *dst)
> {
> type_t charp = LLVMPointerType(LLVMInt8Type(), 0);
> value_t base = LLVMBuildPointerCast(builder, emit_pseudo(src), charp, "");
> value_t idx = LLVMConstInt(LLVMIntType(bits_in_pointer), offset, 0);
> value_t gep = LLVMBuildGEP(builder, base, &idx, 1, "");
> type_t type = LLVMPointerType(emit_type(dst->ctype), 0);
>
> return LLVMBuildPointerCast(builder, gep, type, "");
> }
>
> after which OP_LOAD translation becomes as simple as
>
> case OP_LOAD:
> return LLVMBuildLoad(builder, emit_gep(builder, insn->src,
> insn->offset, insn->target), "");
>
> Jeff, I guess we should do this for output_load() and output_store()
> in sparse-llvm.c as well?
Maybe we can do this for "pointer + integer" as well, using getelementptr
with offset computed by sparse (converting the pointer to char* first).
Unlike inttoptr/ptrtotint, this shouldn't disable LLVM's alias analysis.
I will give it a try later.
- xi
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