Commit Graph

15 Commits

Author SHA1 Message Date
Peter Collingbourne
bb660fc192 Prologue support
Patch by Ben Gamari!

This redefines the `prefix` attribute introduced previously and
introduces a `prologue` attribute.  There are a two primary usecases
that these attributes aim to serve,

  1. Function prologue sigils

  2. Function hot-patching: Enable the user to insert `nop` operations
     at the beginning of the function which can later be safely replaced
     with a call to some instrumentation facility

  3. Runtime metadata: Allow a compiler to insert data for use by the
     runtime during execution. GHC is one example of a compiler that
     needs this functionality for its tables-next-to-code functionality.

Previously `prefix` served cases (1) and (2) quite well by allowing the user
to introduce arbitrary data at the entrypoint but before the function
body. Case (3), however, was poorly handled by this approach as it
required that prefix data was valid executable code.

Here we redefine the notion of prefix data to instead be data which
occurs immediately before the function entrypoint (i.e. the symbol
address). Since prefix data now occurs before the function entrypoint,
there is no need for the data to be valid code.

The previous notion of prefix data now goes under the name "prologue
data" to emphasize its duality with the function epilogue.

The intention here is to handle cases (1) and (2) with prologue data and
case (3) with prefix data.

References
----------

This idea arose out of discussions[1] with Reid Kleckner in response to a
proposal to introduce the notion of symbol offsets to enable handling of
case (3).

[1] http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073235.html

Test Plan: testsuite

Differential Revision: http://reviews.llvm.org/D6454

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223189 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-03 02:08:38 +00:00
Rafael Espindola
2292996e1a Pass a MemoryBufferRef when we can avoid taking ownership.
The attached patch simplifies a few interfaces that don't need to take
ownership of a buffer.

For example, both parseAssembly and parseBitcodeFile will parse the
entire buffer before returning. There is no need to take ownership.

Using a MemoryBufferRef makes it obvious in the type signature that
there is no ownership transfer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216488 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-26 21:49:01 +00:00
Rafael Espindola
81e49922a8 Return a std::unique_ptr from the IRReader.h functions. NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216466 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-26 17:29:46 +00:00
Rafael Espindola
8c96862847 Modernize raw_fd_ostream's constructor a bit.
Take a StringRef instead of a "const char *".
Take a "std::error_code &" instead of a "std::string &" for error.

A create static method would be even better, but this patch is already a bit too
big.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216393 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-25 18:16:47 +00:00
Duncan P. N. Exon Smith
7838818ad7 IR: Implement uselistorder assembly directives
Implement `uselistorder` and `uselistorder_bb` assembly directives,
which allow the use-list order to be recovered when round-tripping to
assembly.

This is the bulk of PR20515.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216025 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 21:30:15 +00:00
Duncan P. N. Exon Smith
13f5c5896d verify-uselistorder: Force -preserve-bc-use-list-order
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216022 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 21:08:27 +00:00
Rafael Espindola
9b29ff99c0 Modernize the .ll parsing interface.
* Use StringRef instead of std::string&
* Return a std::unique_ptr<Module> instead of taking an optional module to write
  to (was not really used).
* Use current comment style.
* Use current naming convention.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215989 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 16:58:54 +00:00
Duncan P. N. Exon Smith
36c150801a verify-uselistorder: Call verifyModule() and improve output
Call `verifyModule()` after parsing and after every transformation.
Also convert some `DEBUG(dbgs())` to `errs()` to increase visibility
into what's going on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215951 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-18 23:44:14 +00:00
Duncan P. N. Exon Smith
1d3169155b verify-uselistorder: Reverse use-lists at every verification
Updated `verify-uselistorder` to more than double the number of use-list
orders it checks.

  - Every time it verifies an order, it then reverses the order and
    verifies again.

  - It now verifies the initial order, before running any shuffles.

Changed the default to `-num-shuffles=1`, since this is already four
checks, and after r214584 shuffling is guaranteed to make a new order.

This is part of PR5680.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214596 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 23:49:41 +00:00
Duncan P. N. Exon Smith
4277019a75 verify-uselistorder: Add missing static
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214595 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 23:31:13 +00:00
Duncan P. N. Exon Smith
b2b0ad4c75 verify-uselistorder: Move shuffleUseLists() out of lib/IR
`shuffleUseLists()` is only used in `verify-uselistorder`, so move it
there to avoid bloating other executables.  As a drive-by, update some
of the header docs.

This is part of PR5680.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214592 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 23:03:36 +00:00
Duncan P. N. Exon Smith
236c1ac873 verify-uselistorder: Make the verification logic easier to reuse
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214587 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 22:52:06 +00:00
Rafael Espindola
9aa0b5e11e Remove some calls to std::move.
Instead of moving out the data in a ErrorOr<std::unique_ptr<Foo>>, get
a reference to it.

Thanks to David Blaikie for the suggestion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214516 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 14:31:55 +00:00
Duncan P. N. Exon Smith
94f7c7aeaa verify-uselistorder: Change the default -num-shuffles=5
Change the default for `-num-shuffles` to 5 and better document the
algorithm in the header docs of `verify-uselistorder`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214419 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-31 18:46:24 +00:00
Duncan P. N. Exon Smith
89c4197256 Rename llvm-uselistorder => verify-uselistorder
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214318 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-30 17:11:27 +00:00