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Philip Reames 288a95fc8c Seperate volatility and atomicity/ordering in SelectionDAG 
At the moment, we mark every atomic memory access as being also volatile. This is unnecessarily conservative and prohibits many legal transforms (DCE, folding, etc..).

This patch removes MOVolatile from the MachineMemOperands of atomic, but not volatile, instructions. This should be strictly NFC after a series of previous patches which have gone in to ensure backend code is conservative about handling of isAtomic MMOs. Once it's in and baked for a bit, we'll start working through removing unnecessary bailouts one by one. We applied this same strategy to the middle end a few years ago, with good success.

To make sure this patch itself is NFC, it is build on top of a series of other patches which adjust code to (for the moment) be as conservative for an atomic access as for a volatile access and build up a test corpus (mostly in test/CodeGen/X86/atomics-unordered.ll)..

Previously landed

    D57593 Fix a bug in the definition of isUnordered on MachineMemOperand
    D57596 [CodeGen] Be conservative about atomic accesses as for volatile
    D57802 Be conservative about unordered accesses for the moment
    rL353959: [Tests] First batch of cornercase tests for unordered atomics.
    rL353966: [Tests] RMW folding tests w/unordered atomic operations.
    rL353972: [Tests] More unordered atomic lowering tests.
    rL353989: [SelectionDAG] Inline a single use helper function, and remove last non-MMO interface
    rL354740: [Hexagon, SystemZ] Be super conservative about atomics
    rL354800: [Lanai] Be super conservative about atomics
    rL354845: [ARM] Be super conservative about atomics

Attention Out of Tree Backend Owners: This patch may break you. If it does, you can use the TLI getMMOFlags hook to restore the MOVolatile to any instruction you need to. (See llvm-dev thread titled "PSA: Changes to how atomics are handled in backends" started Feb 27, 2019.)

Differential Revision: https://reviews.llvm.org/D57601

llvm-svn: 355025
 		2019-02-27 20:20:08 +00:00
clang Add triples to the test I committed in r355012 to fix windows bots. 2019-02-27 18:59:52 +00:00
clang-tools-extra [clang-tidy] Add the abseil-time-subtraction check 2019-02-27 20:08:50 +00:00
compiler-rt [NFC][Sanitizer] Hard-code fast/slow unwinder at call site 2019-02-27 20:01:04 +00:00
debuginfo-tests Set config.lit_tools_dir, which is needed by lit.llvm.initialize. 2018-11-06 21:54:27 +00:00
libclc Adjust documentation for git migration. 2019-01-29 16:37:27 +00:00
libcxx [libc++] Add is_nothrow_convertible from P0758R1 2019-02-27 17:57:38 +00:00
libcxxabi [libcxxabi][CMake] Drop unused HandleOutOfTreeLLVM include 2019-02-18 20:58:06 +00:00
libunwind [CMake] Don't cache LLVM_MAIN_SRC_DIR 2019-02-13 07:09:26 +00:00
lld [DebugInfo] add SectionedAddress to DebugInfo interfaces. 2019-02-27 13:17:36 +00:00
lldb [Reproducer] Make 'reproducer generate' a NOOP during replay. 2019-02-27 17:47:06 +00:00
llgo Adjust documentation for git migration. 2019-01-29 16:37:27 +00:00
llvm Seperate volatility and atomicity/ordering in SelectionDAG 2019-02-27 20:20:08 +00:00
openmp [OpenMP] Fix check-openmp after r354553 2019-02-21 12:00:57 +00:00
parallel-libs Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
polly [opaque pointer types] Update calls to CreateCall to pass the function 2019-02-08 19:30:46 +00:00
pstl [pstl] Remove some warnings when compiling with a recent Clang 2019-02-15 17:30:35 +00:00
.arcconfig Update monorepo .arcconfig with new project callsign. 2019-01-31 14:34:59 +00:00
.clang-format Add .clang-tidy and .clang-format files to the toplevel of the 2019-01-29 16:43:16 +00:00
.clang-tidy Disable tidy checks with too many hits 2019-02-01 11:20:13 +00:00
README.md
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README.md

The LLVM Compiler Infrastructure

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