[llvm] r303210 - [Inliner] Do not mix callsite and callee hotness based updates.

[Easwaran Raman via llvm-commits]

Author: eraman
Date: Tue May 16 16:18:09 2017
New Revision: 303210

URL: http://llvm.org/viewvc/llvm-project?rev=303210&view=rev
Log:
[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

Modified:
    llvm/trunk/lib/Analysis/InlineCost.cpp
    llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll

Modified: llvm/trunk/lib/Analysis/InlineCost.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InlineCost.cpp?rev=303210&r1=303209&r2=303210&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InlineCost.cpp (original)
+++ llvm/trunk/lib/Analysis/InlineCost.cpp Tue May 16 16:18:09 2017
@@ -669,21 +669,33 @@ void CallAnalyzer::updateThreshold(CallS
       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);
+        }
       }
     }
   }

Modified: llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll?rev=303210&r1=303209&r2=303210&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll (original)
+++ llvm/trunk/test/Transforms/Inline/inline-hot-callee.ll Tue May 16 16:18:09 2017
@@ -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