[PATCH] D136774: [Outliner] Add an option to only enable outlining of patterns above a certain threshold

[Nathan Lanza via Phabricator via llvm-commits]

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Outlining isn't always a win when the saved instruction count is >= 1.
The overhead of representing a new function in the binary depends on
exception metadata and alignment. So parameterize this for local tuning.


https://reviews.llvm.org/D136774

Files:
  llvm/lib/CodeGen/MachineOutliner.cpp


Index: llvm/lib/CodeGen/MachineOutliner.cpp
===================================================================
--- llvm/lib/CodeGen/MachineOutliner.cpp
+++ llvm/lib/CodeGen/MachineOutliner.cpp
@@ -113,6 +113,10 @@
     cl::desc(
         "Number of times to rerun the outliner after the initial outline"));
 
+static cl::opt<unsigned> OutlinerBenefitThreshold(
+    "outliner-benefit-threshold", cl::init(1), cl::Hidden,
+    cl::desc("The minimum size before an outlining candidate is accpeted"));
+
 namespace {
 
 /// Maps \p MachineInstrs to unsigned integers and stores the mappings.
@@ -597,7 +601,7 @@
       continue;
 
     // Is it better to outline this candidate than not?
-    if (OF.getBenefit() < 1) {
+    if (OF.getBenefit() < OutlinerBenefitThreshold) {
       emitNotOutliningCheaperRemark(StringLen, CandidatesForRepeatedSeq, OF);
       continue;
     }
@@ -771,7 +775,7 @@
     });
 
     // If we made it unbeneficial to outline this function, skip it.
-    if (OF.getBenefit() < 1)
+    if (OF.getBenefit() < OutlinerBenefitThreshold)
       continue;
 
     // It's beneficial. Create the function and outline its sequence's


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