[PGO] Fix handling of cold entry count for instrumented PGO
Summary:
In r277849, getEntryCount was changed to return None when the entry
count was 0, specifically for SamplePGO where it means no samples were
recorded. However, for instrumentation PGO a 0 entry count should be
returned directly, since it does mean that the function was completely
cold. Otherwise we end up treating these functions conservatively
in isFunctionEntryCold() and isColdBB().
Instead, for SamplePGO use -1 when there are no samples, and change
getEntryCount to return None when the value is -1.
Reviewers: danielcdh, davidxl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41307
llvm-svn: 321018
diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index f0e781b..7086c2e 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -1583,7 +1583,10 @@
}
bool SampleProfileLoader::runOnFunction(Function &F, ModuleAnalysisManager *AM) {
- F.setEntryCount(0);
+ // Initialize the entry count to -1, which will be treated conservatively
+ // by getEntryCount as the same as unknown (None). If we have samples this
+ // will be overwritten in emitAnnotations.
+ F.setEntryCount(-1);
std::unique_ptr<OptimizationRemarkEmitter> OwnedORE;
if (AM) {
auto &FAM =