Use profile info to set function section prefix to group hot/cold functions.
Summary:
The original implementation is in r261607, which was reverted in r269726 to accomendate the ProfileSummaryInfo analysis pass. The new implementation:
1. add a new metadata for function section prefix
2. query against ProfileSummaryInfo in CGP to set the correct section prefix for each function
3. output the section prefix set by CGP
Reviewers: davidxl, eraman
Subscribers: vsk, llvm-commits
Differential Revision: https://reviews.llvm.org/D24989
llvm-svn: 284533
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 62bc755..d102ccb 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -19,6 +19,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
@@ -119,6 +120,10 @@
"disable-preheader-prot", cl::Hidden, cl::init(false),
cl::desc("Disable protection against removing loop preheaders"));
+static cl::opt<bool> ProfileGuidedSectionPrefix(
+ "profile-guided-section-prefix", cl::Hidden, cl::init(true),
+ cl::desc("Use profile info to add section prefix for hot/cold functions"));
+
namespace {
typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
typedef PointerIntPair<Type *, 1, bool> TypeIsSExt;
@@ -168,6 +173,7 @@
void getAnalysisUsage(AnalysisUsage &AU) const override {
// FIXME: When we can selectively preserve passes, preserve the domtree.
+ AU.addRequired<ProfileSummaryInfoWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
@@ -205,8 +211,11 @@
}
char CodeGenPrepare::ID = 0;
-INITIALIZE_TM_PASS(CodeGenPrepare, "codegenprepare",
- "Optimize for code generation", false, false)
+INITIALIZE_TM_PASS_BEGIN(CodeGenPrepare, "codegenprepare",
+ "Optimize for code generation", false, false)
+INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
+INITIALIZE_TM_PASS_END(CodeGenPrepare, "codegenprepare",
+ "Optimize for code generation", false, false)
FunctionPass *llvm::createCodeGenPreparePass(const TargetMachine *TM) {
return new CodeGenPrepare(TM);
@@ -231,6 +240,15 @@
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
OptSize = F.optForSize();
+ if (ProfileGuidedSectionPrefix) {
+ ProfileSummaryInfo *PSI =
+ getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
+ if (PSI->isFunctionEntryHot(&F))
+ F.setSectionPrefix(".hot");
+ else if (PSI->isFunctionEntryCold(&F))
+ F.setSectionPrefix(".cold");
+ }
+
/// This optimization identifies DIV instructions that can be
/// profitably bypassed and carried out with a shorter, faster divide.
if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index edaa778..91cee33 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -296,8 +296,12 @@
} else {
Name = getSectionPrefixForGlobal(Kind);
}
- // FIXME: Extend the section prefix to include hotness catagories such as .hot
- // or .unlikely for functions.
+
+ if (const Function *F = dyn_cast<Function>(GV)) {
+ const auto &OptionalPrefix = F->getSectionPrefix();
+ if (OptionalPrefix)
+ Name += *OptionalPrefix;
+ }
if (EmitUniqueSection && UniqueSectionNames) {
Name.push_back('.');