[llvm] Merge sourcelocation in CSEMIRBuilder::getDominatingInstrForID. (PR #90922)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,67 @@
+# This test checks to make sure that when an instruction (%35 in the test) is 
+# moved due to matching a result of a fold of two other instructions
+# (%16, and %17 in the test) in the legalizer, the DILocation of the 
+# instruction that is moved (%35) is updated appropriately.
+
+# RUN: llc %s -O0 --start-before=legalizer --stop-after=legalizer -o - | FileCheck %s 
----------------
arsenm wrote:

Don't need -O0, and this is the same as -run-pass=legalizer 

https://github.com/llvm/llvm-project/pull/90922