From c8dba682bba9c80654d7a10331f718da9b7b0475 Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson@google.com>
Date: Wed, 24 Oct 2018 18:53:47 +0000
Subject: [hot-cold-split] Name split functions with ".cold" suffix

Summary:
The current default of appending "_"+entry block label to the new
extracted cold function breaks demangling. Change the deliminator from
"_" to "." to enable demangling. Because the header block label will
be empty for release compile code, use "extracted" after the "." when
the label is empty.

Additionally, add a mechanism for the client to pass in an alternate
suffix applied after the ".", and have the hot cold split pass use
"cold."+Count, where the Count is currently 1 but can be used to
uniquely number multiple cold functions split out from the same function
with D53588.

Reviewers: sebpop, hiraditya

Subscribers: llvm-commits, erik.pilkington

Differential Revision: https://reviews.llvm.org/D53534

llvm-svn: 345178
---
 llvm/lib/Transforms/IPO/HotColdSplitting.cpp | 16 +++++++++-------
 llvm/lib/Transforms/Utils/CodeExtractor.cpp  | 16 +++++++++++-----
 2 files changed, 20 insertions(+), 12 deletions(-)

(limited to 'llvm/lib')

diff --git a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
index d3e086e972a..a63cd842241 100644
--- a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -265,7 +265,7 @@ private:
                                     DominatorTree *DT, PostDomTree *PDT);
   Function *extractColdRegion(const SmallVectorImpl<BasicBlock *> &Region,
                               DominatorTree *DT, BlockFrequencyInfo *BFI,
-                              OptimizationRemarkEmitter &ORE);
+                              OptimizationRemarkEmitter &ORE, unsigned Count);
   bool isOutlineCandidate(const SmallVectorImpl<BasicBlock *> &Region,
                           const BasicBlock *Exit) const {
     if (!Exit)
@@ -331,16 +331,18 @@ bool HotColdSplitting::shouldOutlineFrom(const Function &F) const {
   return true;
 }
 
-Function *
-HotColdSplitting::extractColdRegion(const SmallVectorImpl<BasicBlock *> &Region,
-                                    DominatorTree *DT, BlockFrequencyInfo *BFI,
-                                    OptimizationRemarkEmitter &ORE) {
+Function *HotColdSplitting::extractColdRegion(
+    const SmallVectorImpl<BasicBlock *> &Region, DominatorTree *DT,
+    BlockFrequencyInfo *BFI, OptimizationRemarkEmitter &ORE, unsigned Count) {
   assert(!Region.empty());
   LLVM_DEBUG(for (auto *BB : Region)
           llvm::dbgs() << "\nExtracting: " << *BB;);
 
   // TODO: Pass BFI and BPI to update profile information.
-  CodeExtractor CE(Region, DT);
+  CodeExtractor CE(Region, DT, /* AggregateArgs */ false, /* BFI */ nullptr,
+                   /* BPI */ nullptr, /* AllowVarArgs */ false,
+                   /* AllowAlloca */ false,
+                   /* Suffix */ "cold." + std::to_string(Count));
 
   SetVector<Value *> Inputs, Outputs, Sinks;
   CE.findInputsOutputs(Inputs, Outputs, Sinks);
@@ -426,7 +428,7 @@ const Function *HotColdSplitting::outlineColdBlocks(Function &F,
         ++NumColdSESEFound;
         ValidColdRegion.push_back(ExitColdRegion);
         // Candidate for outlining. FIXME: Continue outlining.
-        return extractColdRegion(ValidColdRegion, DT, BFI, ORE);
+        return extractColdRegion(ValidColdRegion, DT, BFI, ORE, /* Count */ 1);
       }
     }
   }
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 27b982578c4..328fe1fac65 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -228,19 +228,21 @@ buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
 CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
                              bool AggregateArgs, BlockFrequencyInfo *BFI,
                              BranchProbabilityInfo *BPI, bool AllowVarArgs,
-                             bool AllowAlloca)
+                             bool AllowAlloca, std::string Suffix)
     : DT(DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
       BPI(BPI), AllowVarArgs(AllowVarArgs),
-      Blocks(buildExtractionBlockSet(BBs, DT, AllowVarArgs, AllowAlloca)) {}
+      Blocks(buildExtractionBlockSet(BBs, DT, AllowVarArgs, AllowAlloca)),
+      Suffix(Suffix) {}
 
 CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs,
                              BlockFrequencyInfo *BFI,
-                             BranchProbabilityInfo *BPI)
+                             BranchProbabilityInfo *BPI, std::string Suffix)
     : DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
       BPI(BPI), AllowVarArgs(false),
       Blocks(buildExtractionBlockSet(L.getBlocks(), &DT,
                                      /* AllowVarArgs */ false,
-                                     /* AllowAlloca */ false)) {}
+                                     /* AllowAlloca */ false)),
+      Suffix(Suffix) {}
 
 /// definedInRegion - Return true if the specified value is defined in the
 /// extracted region.
@@ -669,10 +671,14 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
                   FunctionType::get(RetTy, paramTy,
                                     AllowVarArgs && oldFunction->isVarArg());
 
+  std::string SuffixToUse =
+      Suffix.empty()
+          ? (header->getName().empty() ? "extracted" : header->getName().str())
+          : Suffix;
   // Create the new function
   Function *newFunction = Function::Create(
       funcType, GlobalValue::InternalLinkage, oldFunction->getAddressSpace(),
-      oldFunction->getName() + "_" + header->getName(), M);
+      oldFunction->getName() + "." + SuffixToUse, M);
   // If the old function is no-throw, so is the new one.
   if (oldFunction->doesNotThrow())
     newFunction->setDoesNotThrow();
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