Move "Eliminate Available Externally" immediately after the inliner

This pass is supposed to reduce the size of the IR for compile time
purpose. We should run it ASAP, except when we prepare for LTO or
ThinLTO, and we want to keep them available for link-time inline.

Differential Revision: http://reviews.llvm.org/D19813

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 268394

diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 71ec8ae..7669895 100644 (file)
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -404,6 +404,19 @@ void PassManagerBuilder::populateModulePassManager(
   // we must insert a no-op module pass to reset the pass manager.
   MPM.add(createBarrierNoopPass());
 
+  if (!DisableUnitAtATime && OptLevel > 1 && !PrepareForLTO &&
+      !PrepareForThinLTO)
+    // 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 (!DisableUnitAtATime)
     MPM.add(createReversePostOrderFunctionAttrsPass());
 
@@ -428,18 +441,6 @@ void PassManagerBuilder::populateModulePassManager(
     MPM.add(createLICMPass());                  // Hoist loop invariants
   }
 
-  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 (PerformThinLTO) {
     // Remove dead fns and globals. Removing unreferenced functions could lead
     // to more opportunities for globalopt.

diff --git a/llvm/test/Other/pass-pipelines.ll b/llvm/test/Other/pass-pipelines.ll
index 5e3e38e..5da31cc 100644 (file)
--- a/llvm/test/Other/pass-pipelines.ll
+++ b/llvm/test/Other/pass-pipelines.ll
@@ -55,7 +55,10 @@
 ; Next we break out of the main Function passes inside the CGSCC pipeline with
 ; a barrier pass.
 ; CHECK-O2: A No-Op Barrier Pass
-; Inferring function attribute should be immediately after the CGSCC pipeline.
+; Reduce the size of the IR ASAP after the inliner.
+; CHECK-O2-NEXT: Eliminate Available Externally
+; Inferring function attribute should be right after the CGSCC pipeline, before
+; any other optimizations/analyses.
 ; CHECK-O2-NEXT: CallGraph
 ; CHECK-O2-NEXT: Deduce function attributes in RPO
 ; CHECK-O2-NOT: Manager