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[PassManager] Improve the interaction between -O2 and ThinLTO. 

Run GDCE slightly later so that we don't have to repeat it
twice when preparing for Thin. Thanks to Mehdi for the suggestion.

llvm-svn: 314999
This commit is contained in:
Davide Italiano 2017-10-05 18:23:25 +00:00
parent 957151bd86
commit c8708e59e8
2 changed files with 14 additions and 16 deletions
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24
llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
View File

@ -508,17 +508,6 @@ void PassManagerBuilder::populateModulePassManager(
// we must insert a no-op module pass to reset the pass manager.
MPM.add(createBarrierNoopPass());
// The inliner performs some kind of dead code elimination as it goes,
// but there are cases that are not really caught by it. We might
// at some point consider teaching the inliner about them, but it
// is OK for now to run GlobalOpt + GlobalDCE in tandem as their
// benefits generally outweight the cost, making the whole pipeline
// faster.
if (RunInliner) {
MPM.add(createGlobalOptimizerPass());
MPM.add(createGlobalDCEPass());
}
if (RunPartialInlining)
MPM.add(createPartialInliningPass());
@ -538,12 +527,21 @@ void PassManagerBuilder::populateModulePassManager(
if (!DisableUnitAtATime)
MPM.add(createReversePostOrderFunctionAttrsPass());
// The inliner performs some kind of dead code elimination as it goes,
// but there are cases that are not really caught by it. We might
// at some point consider teaching the inliner about them, but it
// is OK for now to run GlobalOpt + GlobalDCE in tandem as their
// benefits generally outweight the cost, making the whole pipeline
// faster.
if (RunInliner) {
MPM.add(createGlobalOptimizerPass());
MPM.add(createGlobalDCEPass());
}
// If we are planning to perform ThinLTO later, let's not bloat the code with
// unrolling/vectorization/... now. We'll first run the inliner + CGSCC passes
// during ThinLTO and perform the rest of the optimizations afterward.
if (PrepareForThinLTO) {
// Reduce the size of the IR as much as possible.
MPM.add(createGlobalOptimizerPass());
// Rename anon globals to be able to export them in the summary.
MPM.add(createNameAnonGlobalPass());
return;

6
llvm/test/Other/pass-pipelines.ll
View File

@ -55,15 +55,15 @@
; Next we break out of the main Function passes inside the CGSCC pipeline with
; a barrier pass.
; CHECK-O2: A No-Op Barrier Pass
; Reduce the size of the IR ASAP after the inliner.
; CHECK-O2-NEXT: Global Variable Optimizer
; CHECK-O2: Dead Global Elimination
; 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
; Reduce the size of the IR ASAP after the inliner.
; CHECK-O2-NEXT: Global Variable Optimizer
; CHECK-O2: Dead Global Elimination
; Next is the late function pass pipeline.
; CHECK-O2: FunctionPass Manager
; CHECK-O2-NOT: Manager