[llvm] 57412c3 - [GlobalISel] Update the documentation of abd. (#164594)

[via llvm-commits]

Author: David Green
Date: 2025-10-22T13:20:26+01:00
New Revision: 57412c3485c5614348015f37ce69be0f378fcad9

URL: https://github.com/llvm/llvm-project/commit/57412c3485c5614348015f37ce69be0f378fcad9
DIFF: https://github.com/llvm/llvm-project/commit/57412c3485c5614348015f37ce69be0f378fcad9.diff

LOG: [GlobalISel] Update the documentation of abd. (#164594)

The abd nodes do not perform the same as abs(x-y), although they are
often mistaken to do so. They extend into a larger bit size before
performing the sub / abs and so produce different results. Update the
description of the instruction to avoid misunderstandings.

Added: 
    

Modified: 
    llvm/docs/GlobalISel/GenericOpcode.rst

Removed: 
    


################################################################################
diff  --git a/llvm/docs/GlobalISel/GenericOpcode.rst b/llvm/docs/GlobalISel/GenericOpcode.rst
index b055327466739..661a11537cf57 100644
--- a/llvm/docs/GlobalISel/GenericOpcode.rst
+++ b/llvm/docs/GlobalISel/GenericOpcode.rst
@@ -504,7 +504,7 @@ undefined.
 G_ABDS, G_ABDU
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Compute the absolute 
diff erence (signed and unsigned), e.g. abs(x-y).
+Compute the absolute 
diff erence (signed and unsigned), e.g. trunc(abs(ext(x)-ext(y)).
 
 .. code-block:: none