Disable loop unrolling and icp in SamplePGO ThinLTO compile phase
Summary:
loop unrolling and icp will make the sample profile annotation much harder in the backend. So disable these 2 optimization in the ThinLTO compile phase.
Will add a test in cfe in a separate patch.
Reviewers: tejohnson
Reviewed By: tejohnson
Subscribers: mehdi_amini, llvm-commits, Prazek
Differential Revision: https://reviews.llvm.org/D31217
llvm-svn: 298646
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 734f81b..b07b7d1 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -435,6 +435,14 @@
MPM.add(createPGOIndirectCallPromotionLegacyPass(/*InLTO = */ true,
!PGOSampleUse.empty()));
+ // For SamplePGO in ThinLTO compile phase, we do not want to unroll loops
+ // as it will change the CFG too much to make the 2nd profile annotation
+ // in backend more difficult.
+ bool PrepareForThinLTOUsingPGOSampleProfile =
+ PrepareForThinLTO && !PGOSampleUse.empty();
+ if (PrepareForThinLTOUsingPGOSampleProfile)
+ DisableUnrollLoops = true;
+
if (!DisableUnitAtATime) {
// Infer attributes about declarations if possible.
MPM.add(createInferFunctionAttrsLegacyPass());
@@ -453,7 +461,10 @@
MPM.add(createCFGSimplificationPass()); // Clean up after IPCP & DAE
}
- if (!PerformThinLTO) {
+ // For SamplePGO in ThinLTO compile phase, we do not want to do indirect
+ // call promotion as it will change the CFG too much to make the 2nd
+ // profile annotation in backend more difficult.
+ if (!PerformThinLTO && !PrepareForThinLTOUsingPGOSampleProfile) {
/// PGO instrumentation is added during the compile phase for ThinLTO, do
/// not run it a second time
addPGOInstrPasses(MPM);