[LLVMdev] TargetExternalSymbol and TargetGlobalAddress
sabre at nondot.org
Tue Oct 17 11:30:32 PDT 2006
On Mon, 16 Oct 2006, [UTF-8] Rafael Esp?ndola wrote:
> I have noticed that TargetGlobalAddress is generated for "source code"
> functions and TargetExternalSymbol is generated for builtins like
> __lshrdi3. What is the difference between TargetExternalSymbol and
The only real difference is that one exists in the LLVM code and one
doesn't. :) In particular, TargetExternalSymbol's are limited to being
defined in some other module, but TargetGlobalAddress can be defined in
the current module.
TargetExternalSymbol is a somewhat ugly solution to handle things like
"__lshrdi3" or "malloc", which don't necessarily exist in the LLVM .bc
file. Previously we would add new prototypes to represent these things to
the LLVM module, but we aim to have the code generator not modify the
LLVM module at all.
In my opinion, a better overall design would be to have the lowering phase
totally eliminate LLVM GlobalValue references, making everything in the
code generator be a reference to a lowered name. This would simplify
several pieces of code, particularly the x86 backend.
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