[llvm] 1cd1573 - [docs] Make clearer in WritingAnLLVMPass that the legacy PM isn't the default

[Arthur Eubanks via llvm-commits]

Author: Arthur Eubanks
Date: 2021-02-10T15:26:25-08:00
New Revision: 1cd1573f11b835e9b5ce35b01dc9141438f0dd34

URL: https://github.com/llvm/llvm-project/commit/1cd1573f11b835e9b5ce35b01dc9141438f0dd34
DIFF: https://github.com/llvm/llvm-project/commit/1cd1573f11b835e9b5ce35b01dc9141438f0dd34.diff

LOG: [docs] Make clearer in WritingAnLLVMPass that the legacy PM isn't the default

Reviewed By: ychen

Differential Revision: https://reviews.llvm.org/D96452

Added: 
    

Modified: 
    llvm/docs/WritingAnLLVMPass.rst

Removed: 
    


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diff  --git a/llvm/docs/WritingAnLLVMPass.rst b/llvm/docs/WritingAnLLVMPass.rst
index 7a24659e6294..31e0df655a45 100644
--- a/llvm/docs/WritingAnLLVMPass.rst
+++ b/llvm/docs/WritingAnLLVMPass.rst
@@ -34,9 +34,12 @@ We start by showing you how to construct a pass, everything from setting up the
 code, to compiling, loading, and executing it.  After the basics are down, more
 advanced features are discussed.
 
-This document deals with the legacy pass manager. LLVM is transitioning to
-the new pass manager, which has its own way of defining passes. For more
-details, see :doc:`WritingAnLLVMNewPMPass`.
+.. warning::
+  This document deals with the legacy pass manager. LLVM now uses the new
+  pass manager by default, which has its own way of defining passes. For more
+  details, see :doc:`WritingAnLLVMNewPMPass`. To use the legacy pass manager
+  with ``opt``, pass the ``-enable-new-pm=0`` flag to all ``opt``
+  invocations.
 
 Quick Start --- Writing hello world
 ===================================