[PATCH] D24940: [thinlto] Add cold-callsite import heuristic

[Mehdi AMINI via llvm-commits]

mehdi_amini added a comment.

> Not tunned up heuristic, but with this small heuristic there is about +0.10% improvement on SPEC 2006


This is not clear to me: I would expect only a compile time impact on this, why is there a perf improvement?


================
Comment at: lib/Transforms/IPO/FunctionImport.cpp:60
@@ +59,3 @@
+    ImportColdMultiplier("import-cold-multiplier", cl::init(0), cl::Hidden,
+                         cl::value_desc("N"), cl::ZeroOrMore,
+                         cl::desc("Multiply the `import-instr-limit` threshold for "
----------------
ZeroOrMore? Why isn't the default fine?

================
Comment at: lib/Transforms/IPO/FunctionImport.cpp:301
@@ +300,3 @@
+                   ? ImportColdMultiplier
+                   : 1);
+
----------------
Too many nested ternary operator IMO (I think more than one hurt readability in general).


https://reviews.llvm.org/D24940