Following the discussion on cfe-dev, this
moves createEliminateAvailableExternallyPass earlier in the pass pipeline
to save running many ModulePasses on available external functions that are
thrown away anyhow.
Index: lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- lib/Transforms/IPO/PassManagerBuilder.cpp (revision 246535)
+++ lib/Transforms/IPO/PassManagerBuilder.cpp (working copy)
@@ -331,6 +331,19 @@
// we must insert a no-op module pass to reset the pass manager.
MPM.add(createBarrierNoopPass());
+ if (!DisableUnitAtATime && OptLevel > 1 && !PrepareForLTO) {
+ // Remove avail extern fns and globals definitions if we aren't
+ // compiling an object file for later LTO. For LTO we want to preserve
+ // these so they are eligible for inlining at link-time. Note if they
+ // are unreferenced they will be removed by GlobalDCE later, so
+ // this only impacts referenced available externally globals.
+ // Eventually they will be suppressed during codegen, but eliminating
+ // here enables more opportunity for GlobalDCE as it may make
+ // globals referenced by available external functions dead
+ // and saves running remaining passes on the eliminated functions.
+ MPM.add(createEliminateAvailableExternallyPass());
+ }
+
if (EnableNonLTOGlobalsModRef)
// We add a fresh GlobalsModRef run at this point. This is particularly
// useful as the above will have inlined, DCE'ed, and function-attr
@@ -438,17 +451,6 @@
// GlobalOpt already deletes dead functions and globals, at -O2 try a
// late pass of GlobalDCE. It is capable of deleting dead cycles.
if (OptLevel > 1) {
- if (!PrepareForLTO) {
- // Remove avail extern fns and globals definitions if we aren't
- // compiling an object file for later LTO. For LTO we want to preserve
- // these so they are eligible for inlining at link-time. Note if they
- // are unreferenced they will be removed by GlobalDCE below, so
- // this only impacts referenced available externally globals.
- // Eventually they will be suppressed during codegen, but eliminating
- // here enables more opportunity for GlobalDCE as it may make
- // globals referenced by available external functions dead.
- MPM.add(createEliminateAvailableExternallyPass());
- }
MPM.add(createGlobalDCEPass()); // Remove dead fns and globals.
MPM.add(createConstantMergePass()); // Merge dup global constants
}
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