[LLVMdev] [RFC] Stripping unusable intrinsics

Hal Finkel hfinkel at anl.gov
Wed Dec 10 16:04:15 PST 2014


How much do you save by doing this?


----- Original Message -----
> From: "Chris Bieneman" <beanz at apple.com>
> To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Sent: Wednesday, December 10, 2014 5:53:31 PM
> Subject: [LLVMdev] [RFC] Stripping unusable intrinsics
> llvm-dev,
> In my ongoing saga to improve LLVM for embedded use, we would like to
> support stripping out unused intrinsics based on the LLVM targets
> actually being built.
> I’ve attached two patches.
> The first is a new flag for tablegen to take a list of targets. If
> passed tablegen will only emit intrinsics that either have empty
> target prefixes, or target prefixes matching one of the targets in
> the list. If the flag is not passed the behavior is unchanged. This
> patch can land today (subject to review).
> The second patch is a WIP, and adds support to the CMake build system
> for using the new tablegen flag, and for generating a new
> llvm/Config/llvm-targets.h header which contains defines for each
> target specified with LLVM_TARGETS_TO_BUILD.
> This new header will allow us to #ifdef code using target-specific
> intrinsics outside the targets, thus allowing us to strip out all
> the unused intrinsics.
> -Chris
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Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory

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