[SampleFDO] handle ProfileSampleAccurate when initializing function entry count
ProfileSampleAccurate is used to indicate the profile has exact match to the
code to be optimized.
Previously ProfileSampleAccurate is handled in ProfileSummaryInfo::isColdCallSite
and ProfileSummaryInfo::isColdBlock. A better solution is to initialize function
entry count to 0 when ProfileSampleAccurate is true, so we don't have to handle
ProfileSampleAccurate in multiple places.
Differential Revision: https://reviews.llvm.org/D55660
llvm-svn: 349088
diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index 37f1ea4..06a1ce8 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -123,6 +123,12 @@
cl::desc("Use this option to turn off/on warnings about function with "
"samples but without debug information to use those samples. "));
+static cl::opt<bool> ProfileSampleAccurate(
+ "profile-sample-accurate", cl::Hidden, cl::init(false),
+ cl::desc("If the sample profile is accurate, we will mark all un-sampled "
+ "callsite and function as having 0 samples. Otherwise, treat "
+ "un-sampled callsites and functions conservatively as unknown. "));
+
namespace {
using BlockWeightMap = DenseMap<const BasicBlock *, uint64_t>;
@@ -1604,10 +1610,18 @@
}
bool SampleProfileLoader::runOnFunction(Function &F, ModuleAnalysisManager *AM) {
- // 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(ProfileCount(-1, Function::PCT_Real));
+ // By default the entry count is initialized to -1, which will be treated
+ // conservatively by getEntryCount as the same as unknown (None). This is
+ // to avoid newly added code to be treated as cold. If we have samples
+ // this will be overwritten in emitAnnotations.
+ // If ProfileSampleAccurate is true or F has profile-sample-accurate
+ // attribute, initialize the entry count to 0 so callsites or functions
+ // unsampled will be treated as cold.
+ uint64_t initialEntryCount =
+ (ProfileSampleAccurate || F.hasFnAttribute("profile-sample-accurate"))
+ ? 0
+ : -1;
+ F.setEntryCount(ProfileCount(initialEntryCount, Function::PCT_Real));
std::unique_ptr<OptimizationRemarkEmitter> OwnedORE;
if (AM) {
auto &FAM =