Commit Graph

7 Commits

Author SHA1 Message Date
Eric Christopher cee313d288 Revert "Temporarily Revert "Add basic loop fusion pass.""
The reversion apparently deleted the test/Transforms directory.

Will be re-reverting again.

llvm-svn: 358552
2019-04-17 04:52:47 +00:00
Eric Christopher a863435128 Temporarily Revert "Add basic loop fusion pass."
As it's causing some bot failures (and per request from kbarton).

This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.

llvm-svn: 358546
2019-04-17 02:12:23 +00:00
Peter Collingbourne 001052a067 WholeProgramDevirt: Create bitcast to i8* at each virtual call site.
We can't reuse the llvm.assume instruction's bitcast because it may not
dominate every user of the vtable pointer.

Differential Revision: https://reviews.llvm.org/D36994

llvm-svn: 311491
2017-08-22 21:41:19 +00:00
Peter Collingbourne 184773d81f WholeProgramDevirt: For VCP use a 32-bit ConstantInt for the byte offset.
A future change will cause this byte offset to be inttoptr'd and then exported
via an absolute symbol. On the importing end we will expect the symbol to be
in range [0,2^32) so that it will fit into a 32-bit relocation. The problem
is that on 64-bit architectures if the offset is negative it will not be in
the correct range once we inttoptr it.

This change causes us to use a 32-bit integer so that it can be inttoptr'd
(which zero extends) into the correct range.

Differential Revision: https://reviews.llvm.org/D30016

llvm-svn: 295487
2017-02-17 19:43:45 +00:00
Peter Collingbourne 0312f614b1 IR: Introduce llvm.type.checked.load intrinsic.
This intrinsic safely loads a function pointer from a virtual table pointer
using type metadata. This intrinsic is used to implement control flow integrity
in conjunction with virtual call optimization. The virtual call optimization
pass will optimize away llvm.type.checked.load intrinsics associated with
devirtualized calls, thereby removing the type check in cases where it is
not needed to enforce the control flow integrity constraint.

This patch also introduces the capability to copy type metadata between
global variables, and teaches the virtual call optimization pass to do so.

Differential Revision: http://reviews.llvm.org/D21121

llvm-svn: 273756
2016-06-25 00:23:04 +00:00
Peter Collingbourne 7efd750607 IR: New representation for CFI and virtual call optimization pass metadata.
The bitset metadata currently used in LLVM has a few problems:

1. It has the wrong name. The name "bitset" refers to an implementation
   detail of one use of the metadata (i.e. its original use case, CFI).
   This makes it harder to understand, as the name makes no sense in the
   context of virtual call optimization.

2. It is represented using a global named metadata node, rather than
   being directly associated with a global. This makes it harder to
   manipulate the metadata when rebuilding global variables, summarise it
   as part of ThinLTO and drop unused metadata when associated globals are
   dropped. For this reason, CFI does not currently work correctly when
   both CFI and vcall opt are enabled, as vcall opt needs to rebuild vtable
   globals, and fails to associate metadata with the rebuilt globals. As I
   understand it, the same problem could also affect ASan, which rebuilds
   globals with a red zone.

This patch solves both of those problems in the following way:

1. Rename the metadata to "type metadata". This new name reflects how
   the metadata is currently being used (i.e. to represent type information
   for CFI and vtable opt). The new name is reflected in the name for the
   associated intrinsic (llvm.type.test) and pass (LowerTypeTests).

2. Attach metadata directly to the globals that it pertains to, rather
   than using the "llvm.bitsets" global metadata node as we are doing now.
   This is done using the newly introduced capability to attach
   metadata to global variables (r271348 and r271358).

See also: http://lists.llvm.org/pipermail/llvm-dev/2016-June/100462.html

Differential Revision: http://reviews.llvm.org/D21053

llvm-svn: 273729
2016-06-24 21:21:32 +00:00
Peter Collingbourne df49d1bbb2 WholeProgramDevirt: introduce.
This pass implements whole program optimization of virtual calls in cases
where we know (via bitset information) that the list of callees is fixed. This
includes the following:

- Single implementation devirtualization: if a virtual call has a single
  possible callee, replace all calls with a direct call to that callee.

- Virtual constant propagation: if the virtual function's return type is an
  integer <=64 bits and all possible callees are readnone, for each class and
  each list of constant arguments: evaluate the function, store the return
  value alongside the virtual table, and rewrite each virtual call as a load
  from the virtual table.

- Uniform return value optimization: if the conditions for virtual constant
  propagation hold and each function returns the same constant value, replace
  each virtual call with that constant.

- Unique return value optimization for i1 return values: if the conditions
  for virtual constant propagation hold and a single vtable's function
  returns 0, or a single vtable's function returns 1, replace each virtual
  call with a comparison of the vptr against that vtable's address.

Differential Revision: http://reviews.llvm.org/D16795

llvm-svn: 260312
2016-02-09 22:50:34 +00:00