[llvm] [SelectOptimize] Enable by default; add no-PGO density heuristic; fix… (PR #200691)

[Craig Topper via llvm-commits]

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@@ -7730,9 +7730,12 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
   if (DisableSelectToBranch)
     return false;
 
-  // If the SelectOptimize pass is enabled, selects have already been optimized.
-  if (!getCGPassBuilderOption().DisableSelectOptimize)
-    return false;
+  // SelectOptimize (IR-level) and CodeGenPrepare use complementary heuristics:
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topperc wrote:

I don't think we need a comment to describe why code was removed. If someone wants to add it back, they would need to justify it.

https://github.com/llvm/llvm-project/pull/200691