[llvm] 6869e6c - [InlineCost] Make cost-benefit decision explicit

[Wenlei He via llvm-commits]

Author: Wenlei He
Date: 2021-03-24T16:10:58-07:00
New Revision: 6869e6c1e7f88d06a5db44e46933843247887040

URL: https://github.com/llvm/llvm-project/commit/6869e6c1e7f88d06a5db44e46933843247887040
DIFF: https://github.com/llvm/llvm-project/commit/6869e6c1e7f88d06a5db44e46933843247887040.diff

LOG: [InlineCost] Make cost-benefit decision explicit

With cost-benefit analysis for inlining, we bypass the cost-threshold by returning inline result from call analyzer early.

However the cost and threshold are still available from call analyzer, and when cost is actually higher than threshold, we incorrect set the reason.

The change makes the decision from cost-benefit analysis explicit. It's mostly NFC, except that it allows the priority-based sample loader inliner used by CSSPGO to use cost-benefit heuristic.

Differential Revision: https://reviews.llvm.org/D99302

Added: 
    

Modified: 
    llvm/lib/Analysis/InlineCost.cpp
    llvm/test/Other/optimization-remarks-auto.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index 393efa8bfc6f8..fd4e1a18817b8 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -489,6 +489,9 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
   // sense that it's not weighted by profile counts at all.
   int ColdSize = 0;
 
+  // Whether inlining is decided by cost-benefit analysis.
+  bool DecidedByCostBenefit = false;
+
   bool SingleBB = true;
 
   unsigned SROACostSavings = 0;
@@ -832,6 +835,7 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
       Threshold -= VectorBonus / 2;
 
     if (auto Result = costBenefitAnalysis()) {
+      DecidedByCostBenefit = true;
       if (Result.getValue())
         return InlineResult::success();
       else
@@ -933,6 +937,7 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
   virtual ~InlineCostCallAnalyzer() {}
   int getThreshold() { return Threshold; }
   int getCost() { return Cost; }
+  bool wasDecidedByCostBenefit() { return DecidedByCostBenefit; }
 };
 } // namespace
 
@@ -2616,6 +2621,16 @@ InlineCost llvm::getInlineCost(
 
   LLVM_DEBUG(CA.dump());
 
+  // Always make cost benefit based decision explicit.
+  // We use always/never here since threshold is not meaningful,
+  // as it's not what drives cost-benefit analysis.
+  if (CA.wasDecidedByCostBenefit()) {
+    if (ShouldInline.isSuccess())
+      return InlineCost::getAlways("benefit over cost");
+    else
+      return InlineCost::getNever("cost over benefit");
+  }
+
   // Check if there was a reason to force inlining or no inlining.
   if (!ShouldInline.isSuccess() && CA.getCost() < CA.getThreshold())
     return InlineCost::getNever(ShouldInline.getFailureReason());

diff  --git a/llvm/test/Other/optimization-remarks-auto.ll b/llvm/test/Other/optimization-remarks-auto.ll
index c534167364952..cdedefce78a83 100644
--- a/llvm/test/Other/optimization-remarks-auto.ll
+++ b/llvm/test/Other/optimization-remarks-auto.ll
@@ -10,14 +10,14 @@
 ; RUN: FileCheck %s -check-prefix=YAML-MISS < %t.yaml
 
 ;; test 'auto' threshold
-; RUN: opt < %s --disable-output --enable-new-pm \
+; RUN: opt < %s --disable-output --enable-new-pm --inline-enable-cost-benefit-analysis=0 \
 ; RUN: --passes='module(print-profile-summary,cgscc(inline))' \
 ; RUN: --pass-remarks-output=%t.hot.yaml --pass-remarks-filter='inline' \
 ; RUN: --pass-remarks-with-hotness --pass-remarks-hotness-threshold=auto 2>&1 | FileCheck %s
 ; RUN: FileCheck %s -check-prefix=YAML-PASS < %t.hot.yaml
 ; RUN: not FileCheck %s -check-prefix=YAML-MISS < %t.hot.yaml
 
-; RUN: opt < %s --disable-output --enable-new-pm \
+; RUN: opt < %s --disable-output --enable-new-pm --inline-enable-cost-benefit-analysis=0  \
 ; RUN: --passes='module(print-profile-summary,cgscc(inline))' \
 ; RUN: --pass-remarks=inline --pass-remarks-missed=inline --pass-remarks-analysis=inline \
 ; RUN: --pass-remarks-with-hotness --pass-remarks-hotness-threshold=auto 2>&1 | FileCheck %s -check-prefix=CHECK-RPASS
@@ -82,4 +82,3 @@ entry:
 !12 = !{i32 10000, i64 100, i32 1}
 !13 = !{i32 999000, i64 100, i32 1}
 !14 = !{i32 999999, i64 1, i32 2}
-