[llvm] 669ddd1 - Turn on the new pass manager by default

[Arthur Eubanks via llvm-commits]

Author: Arthur Eubanks
Date: 2021-02-03T14:37:46-08:00
New Revision: 669ddd1e9b1226432b003dbba05b99f8e992285b

URL: https://github.com/llvm/llvm-project/commit/669ddd1e9b1226432b003dbba05b99f8e992285b
DIFF: https://github.com/llvm/llvm-project/commit/669ddd1e9b1226432b003dbba05b99f8e992285b.diff

LOG: Turn on the new pass manager by default

This turns on the new pass manager by default for the optimization pipeline in
Clang and ThinLTO in various LLD backends. This also makes uses of `opt
-instcombine` use the new pass manager (unless specifically opted out).

This does not affect the backend target-dependent codegen pipeline.

If this causes regressions, you can opt out of the new pass manager
either via the -DENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=OFF CMake flag
while building LLVM, or via various compiler flags, e.g.
-flegacy-pass-manager for Clang or -Wl,--lto-legacy-pass-manager for
ELF LLD. Please file bugs for any regressions.

Major differences:
* The inliner works slightly differently
* -O1 does some amount of inlining
* LCSSA and LoopSimplify are run before all loop passes
* Loop unswitching is implemented slightly differently
* A new SpeculateAroundPHIs pass is added to the pipeline

https://lists.llvm.org/pipermail/llvm-dev/2021-January/148098.html

Reviewed By: asbirlea, ychen, MaskRay, echristo

Differential Revision: https://reviews.llvm.org/D95380

Added: 
    

Modified: 
    llvm/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 1affc289e64b..f5298de9f7ca 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -688,8 +688,8 @@ else()
 endif()
 option(LLVM_ENABLE_PLUGINS "Enable plugin support" ${LLVM_ENABLE_PLUGINS_default})
 
-set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER FALSE CACHE BOOL
-  "Enable the experimental new pass manager by default.")
+set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER TRUE CACHE BOOL
+  "Enable the new pass manager by default.")
 
 include(HandleLLVMOptions)