[llvm] 7f24e57 - [MLInliner] Don't inline call sites in unreachable basic blocks

[Mircea Trofin via llvm-commits]

Author: Mircea Trofin
Date: 2022-06-16T09:14:22-07:00
New Revision: 7f24e574d434eb54675abb452b7e673302e7bd3d

URL: https://github.com/llvm/llvm-project/commit/7f24e574d434eb54675abb452b7e673302e7bd3d
DIFF: https://github.com/llvm/llvm-project/commit/7f24e574d434eb54675abb452b7e673302e7bd3d.diff

LOG: [MLInliner] Don't inline call sites in unreachable basic blocks

This requires DominatorTree be updated, which we do in the ml inliner
case, but not in the default case, and the cost of doing so is
noticeable to compile time for the latter[1]. So the patch only affects
the ML inliner.

[1] https://llvm-compile-time-tracker.com/compare.php?from=9fc0aa45e3312944431ba7e1ca0cec99c613992b&to=7af461b1ce0d9138211ef5f883f35d5b9ddf47be&stat=wall-time

Differential Revision: https://reviews.llvm.org/D127899

Added: 
    llvm/test/Transforms/Inline/ML/skip-unreachable.ll

Modified: 
    llvm/include/llvm/Analysis/MLInlineAdvisor.h
    llvm/lib/Analysis/MLInlineAdvisor.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Analysis/MLInlineAdvisor.h b/llvm/include/llvm/Analysis/MLInlineAdvisor.h
index 290726e652acd..00e8d7d7dd4de 100644
--- a/llvm/include/llvm/Analysis/MLInlineAdvisor.h
+++ b/llvm/include/llvm/Analysis/MLInlineAdvisor.h
@@ -65,7 +65,8 @@ class MLInlineAdvisor : public InlineAdvisor {
 
 private:
   int64_t getModuleIRSize() const;
-
+  std::unique_ptr<InlineAdvice>
+  getSkipAdviceIfUnreachableCallsite(CallBase &CB);
   void print(raw_ostream &OS) const override;
 
   mutable DenseMap<const Function *, FunctionPropertiesInfo> FPICache;

diff  --git a/llvm/lib/Analysis/MLInlineAdvisor.cpp b/llvm/lib/Analysis/MLInlineAdvisor.cpp
index edc8eac31b7eb..1a7cdc38471bb 100644
--- a/llvm/lib/Analysis/MLInlineAdvisor.cpp
+++ b/llvm/lib/Analysis/MLInlineAdvisor.cpp
@@ -277,6 +277,9 @@ FunctionPropertiesInfo &MLInlineAdvisor::getCachedFPI(Function &F) const {
 }
 
 std::unique_ptr<InlineAdvice> MLInlineAdvisor::getAdviceImpl(CallBase &CB) {
+  if (auto Skip = getSkipAdviceIfUnreachableCallsite(CB))
+    return Skip;
+
   auto &Caller = *CB.getCaller();
   auto &Callee = *CB.getCalledFunction();
 
@@ -376,9 +379,19 @@ MLInlineAdvisor::getAdviceFromModel(CallBase &CB,
       this, CB, ORE, static_cast<bool>(ModelRunner->evaluate<int64_t>()));
 }
 
+std::unique_ptr<InlineAdvice>
+MLInlineAdvisor::getSkipAdviceIfUnreachableCallsite(CallBase &CB) {
+  if (!FAM.getResult<DominatorTreeAnalysis>(*CB.getCaller())
+           .isReachableFromEntry(CB.getParent()))
+    return std::make_unique<InlineAdvice>(this, CB, getCallerORE(CB), false);
+  return nullptr;
+}
+
 std::unique_ptr<InlineAdvice> MLInlineAdvisor::getMandatoryAdvice(CallBase &CB,
                                                                   bool Advice) {
   // Make sure we track inlinings in all cases - mandatory or not.
+  if (auto Skip = getSkipAdviceIfUnreachableCallsite(CB))
+    return Skip;
   if (Advice && !ForceStop)
     return getMandatoryAdviceImpl(CB);
 

diff  --git a/llvm/test/Transforms/Inline/ML/skip-unreachable.ll b/llvm/test/Transforms/Inline/ML/skip-unreachable.ll
new file mode 100644
index 0000000000000..47a75c3ad898b
--- /dev/null
+++ b/llvm/test/Transforms/Inline/ML/skip-unreachable.ll
@@ -0,0 +1,46 @@
+; Test skipping inlining when the callsite is unreachable (for both mandatory
+; and non-mandatory cases)
+; REQUIRES: llvm_inliner_model_autogenerated
+; RUN: opt -passes=inliner-ml-advisor-release -S < %s | FileCheck %s --check-prefix=CHECK
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-grtev4-linux-gnu"
+
+; Mandatory case
+define i32 @f1() {
+entry:
+  br label %exit
+some_bb:  ; unreachable - has no predecessors
+  %r = call i32 @f2()
+  br label %exit
+exit:
+  ret i32 1
+}
+
+define i32 @f2() #0 {
+  ret i32 2
+}
+
+; Non-mandatory case
+define i32 @f3() {
+entry:
+  br label %exit
+some_bb:  ; unreachable - has no predecessors
+  %r = call i32 @f4()
+  br label %exit
+exit:
+  ret i32 1
+}
+
+define i32 @f4() {
+  ret i32 2
+}
+
+attributes #0 = { alwaysinline }
+
+; CHECK-LABEL: @f1
+; CHECK-LABEL: some_bb
+; CHECK-NEXT: call i32 @f2
+; CHECK-LABEL: @f3
+; CHECK-LABEL: some_bb
+; CHECK-NEXT: call i32 @f4