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Tim Renouf abd85fb1f5 [AMDGPU] Reworked SIFixWWMLiveness 
Summary:
I encountered some problems with SIFixWWMLiveness when WWM is in a loop:

1. It sometimes gave invalid MIR where there is some control flow path
   to the new implicit use of a register on EXIT_WWM that does not pass
   through any def.

2. There were lots of false positives of registers that needed to have
   an implicit use added to EXIT_WWM.

3. Adding an implicit use to EXIT_WWM (and adding an implicit def just
   before the WWM code, which I tried in order to fix (1)) caused lots
   of the values to be spilled and reloaded unnecessarily.

This commit is a rework of SIFixWWMLiveness, with the following changes:

1. Instead of considering any register with a def that can reach the WWM
   code and a def that can be reached from the WWM code, it now
   considers three specific cases that need to be handled.

2. A register that needs liveness over WWM to be synthesized now has it
   done by adding itself as an implicit use to defs other than the
   dominant one.

Also added the following fixmes:

FIXME: We should detect whether a register in one of the above
categories is already live at the WWM code before deciding to add the
implicit uses to synthesize its liveness.

FIXME: I believe this whole scheme may be flawed due to the possibility
of the register allocator doing live interval splitting.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D46756

Change-Id: Ie7fba0ede0378849181df3f1a9a7a39ed1a94a94
llvm-svn: 338783
 		2018-08-02 23:31:32 +00:00
clang [analyzer] Detect pointers escaped after ReturnStmt execution in MallocChecker. 2018-08-02 23:02:08 +00:00
clang-tools-extra Reland "[clang-doc] Refactoring mapper to map by scope" 2018-08-02 20:10:17 +00:00
compiler-rt [libFuzzer] Initial implementation of weighted mutation leveraging during runtime. 2018-08-02 22:30:03 +00:00
debuginfo-tests [DWARF] Change a test to ensure the creation of a __debug_ranges section. 2018-07-31 19:37:29 +00:00
libclc atom: Use volatile pointers for cl_khr_{global,local}_int32_{base,extended}_atomics 2018-06-21 19:27:39 +00:00
libcxx Implement P1023: constexpr comparison operators for std::array 2018-08-02 02:11:06 +00:00
libcxxabi [itanium demangler] Support dot suffixes on block invocation functions 2018-08-02 17:45:01 +00:00
libunwind Bump version number to 8.0.0svn 2018-08-01 15:22:27 +00:00
lld Set IsUsedInRegularObj in a consistent manor between COFF, ELF and wasm. NFC 2018-08-02 20:39:19 +00:00
lldb [lldb] Remove unused variable. 2018-08-02 21:45:05 +00:00
llgo Update copyright year to 2018. 2018-06-18 12:22:17 +00:00
llvm [AMDGPU] Reworked SIFixWWMLiveness 2018-08-02 23:31:32 +00:00
openmp [OpenMP] Fix doacross testing for gcc 2018-08-02 19:13:07 +00:00
parallel-libs Update copyright year to 2018. 2018-06-18 12:22:17 +00:00
polly [JSONExporter] Print instead of ignoring parser error. 2018-08-02 00:11:14 +00:00
README.md
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README.md

Low Level Virtual Machine (LLVM)

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.