From 6479eca14de4d1ad9c04965b2e56a9259bec229f Mon Sep 17 00:00:00 2001
From: Easwaran Raman <eraman@google.com>
Date: Tue, 16 May 2017 21:18:09 +0000
Subject: [PATCH] [Inliner] Do not mix callsite and callee hotness based
 updates.

Update threshold based on callee's hotness only when BFI is not available.
Otherwise use only callsite's hotness. This makes it easier to reason about
hotness related threshold updates.

Differential revision: https://reviews.llvm.org/D33157

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303210 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/InlineCost.cpp                 | 42 +++++++++++++--------
 test/Transforms/Inline/inline-hot-callee.ll | 10 ++---
 2 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index 44c14cb17c2..4702569126c 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/lib/Analysis/InlineCost.cpp
@@ -669,21 +669,33 @@ void CallAnalyzer::updateThreshold(CallSite CS, Function &Callee) {
       Threshold = MaxIfValid(Threshold, Params.HintThreshold);
     if (PSI) {
       BlockFrequencyInfo *CallerBFI = GetBFI ? &((*GetBFI)(*Caller)) : nullptr;
-      if (PSI->isHotCallSite(CS, CallerBFI)) {
-        DEBUG(dbgs() << "Hot callsite.\n");
-        Threshold = Params.HotCallSiteThreshold.getValue();
-      } else if (PSI->isFunctionEntryHot(&Callee)) {
-        DEBUG(dbgs() << "Hot callee.\n");
-        // If callsite hotness can not be determined, we may still know
-        // that the callee is hot and treat it as a weaker hint for threshold
-        // increase.
-        Threshold = MaxIfValid(Threshold, Params.HintThreshold);
-      } else if (PSI->isColdCallSite(CS, CallerBFI)) {
-        DEBUG(dbgs() << "Cold callsite.\n");
-        Threshold = MinIfValid(Threshold, Params.ColdCallSiteThreshold);
-      } else if (PSI->isFunctionEntryCold(&Callee)) {
-        DEBUG(dbgs() << "Cold callee.\n");
-        Threshold = MinIfValid(Threshold, Params.ColdThreshold);
+      // FIXME: After switching to the new passmanager, simplify the logic below
+      // by checking only the callsite hotness/coldness. The check for CallerBFI
+      // exists only because we do not have BFI available with the old PM.
+      //
+      // Use callee's hotness information only if we have no way of determining
+      // callsite's hotness information. Callsite hotness can be determined if
+      // sample profile is used (which adds hotness metadata to calls) or if
+      // caller's BlockFrequencyInfo is available.
+      if (CallerBFI || PSI->hasSampleProfile()) {
+        if (PSI->isHotCallSite(CS, CallerBFI)) {
+          DEBUG(dbgs() << "Hot callsite.\n");
+          Threshold = Params.HotCallSiteThreshold.getValue();
+        } else if (PSI->isColdCallSite(CS, CallerBFI)) {
+          DEBUG(dbgs() << "Cold callsite.\n");
+          Threshold = MinIfValid(Threshold, Params.ColdCallSiteThreshold);
+        }
+      } else {
+        if (PSI->isFunctionEntryHot(&Callee)) {
+          DEBUG(dbgs() << "Hot callee.\n");
+          // If callsite hotness can not be determined, we may still know
+          // that the callee is hot and treat it as a weaker hint for threshold
+          // increase.
+          Threshold = MaxIfValid(Threshold, Params.HintThreshold);
+        } else if (PSI->isFunctionEntryCold(&Callee)) {
+          DEBUG(dbgs() << "Cold callee.\n");
+          Threshold = MinIfValid(Threshold, Params.ColdThreshold);
+        }
       }
     }
   }
diff --git a/test/Transforms/Inline/inline-hot-callee.ll b/test/Transforms/Inline/inline-hot-callee.ll
index da6e52343b2..dad57440063 100644
--- a/test/Transforms/Inline/inline-hot-callee.ll
+++ b/test/Transforms/Inline/inline-hot-callee.ll
@@ -1,10 +1,10 @@
 ; RUN: opt < %s -inline -inline-threshold=0 -inlinehint-threshold=100 -S | FileCheck %s
-; RUN: opt < %s -passes='require<profile-summary>,cgscc(inline)' -inline-threshold=0 -inlinehint-threshold=100 -S | FileCheck %s
 
-; This tests that a hot callee gets the (higher) inlinehint-threshold even without
-; inline hints and gets inlined because the cost is less than inlinehint-threshold.
-; A cold callee with identical body does not get inlined because cost exceeds the
-; inline-threshold
+; This tests that a hot callee gets the (higher) inlinehint-threshold even
+; without inline hints and gets inlined because the cost is less than
+; inlinehint-threshold. A cold callee with identical body does not get inlined
+; because cost exceeds the inline-threshold. This test is relevant only when the
+; old pass manager is used.
 
 define i32 @callee1(i32 %x) !prof !21 {
   %x1 = add i32 %x, 1
-- 
2.40.0