[PATCH] D120584: [NewPM][Inliner] Mark inlined calls to functions in same SCC as callee as noinline

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks created this revision.
Herald added subscribers: ormris, hiraditya.
Herald added a reviewer: ctetreau.
aeubanks requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

When processing the list of calls created by inlining, check each call
to see if the new call's callee is in the same SCC as the original
callee's. If so, mark the call as noinline.

This is an alternative to D98481 <https://reviews.llvm.org/D98481>, which forbids inlining functions in a
non-trivial SCC at all. This allows us to do one level of inlining, plus
inlining of any other calls to functions outside the SCC.

Hopefully fixes PR45253.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D120584

Files:
  llvm/lib/Transforms/IPO/Inliner.cpp
  llvm/test/Transforms/Inline/mut-rec-scc.ll


Index: llvm/test/Transforms/Inline/mut-rec-scc.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Inline/mut-rec-scc.ll
@@ -0,0 +1,68 @@
+; RUN: opt -S -passes='cgscc(inline,instcombine)' < %s | FileCheck %s
+
+; We use call to a dummy function to avoid inlining test1 into test2 or vice
+; versa, such that we aren't left with a trivial cycle, as trivial cycles are
+; special-cased to never be inlined.
+; However, InstCombine will eliminate these calls after inlining, and thus
+; make the functions eligible for inlining in their callers.
+declare void @dummy() readnone nounwind willreturn
+
+define void @test1() {
+; CHECK-LABEL: define void @test1(
+; CHECK-NEXT:    call void @test2()
+; CHECK-NEXT:    call void @test2()
+; CHECK-NEXT:    ret void
+;
+  call void @test2()
+  call void @test2()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  ret void
+}
+
+define void @test2() {
+; CHECK-LABEL: define void @test2(
+; CHECK-NEXT:    call void @test1()
+; CHECK-NEXT:    call void @test1()
+; CHECK-NEXT:    ret void
+;
+  call void @test1()
+  call void @test1()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  call void @dummy()
+  ret void
+}
+
+; We should inline the @test2 calls and mark the inlined @test1 calls as noinline
+define void @test3() {
+; CHECK-LABEL: define void @test3(
+; CHECK-NEXT:    call void @test1() #[[NOINLINE:[0-9]+]]
+; CHECK-NEXT:    call void @test1() #[[NOINLINE]]
+; CHECK-NEXT:    call void @test1() #[[NOINLINE]]
+; CHECK-NEXT:    call void @test1() #[[NOINLINE]]
+; CHECK-NEXT:    ret void
+;
+  call void @test2()
+  call void @test2()
+  ret void
+}
+
+; CHECK: [[NOINLINE]] = { noinline }
\ No newline at end of file
Index: llvm/lib/Transforms/IPO/Inliner.cpp
===================================================================
--- llvm/lib/Transforms/IPO/Inliner.cpp
+++ llvm/lib/Transforms/IPO/Inliner.cpp
@@ -935,9 +935,15 @@
             if (tryPromoteCall(*ICB))
               NewCallee = ICB->getCalledFunction();
           }
-          if (NewCallee)
-            if (!NewCallee->isDeclaration())
+          if (NewCallee) {
+            if (!NewCallee->isDeclaration()) {
               Calls->push({ICB, NewHistoryID});
+              if (CG.lookupSCC(CG.get(Callee)) ==
+                  CG.lookupSCC(CG.get(*NewCallee))) {
+                ICB->addFnAttr(Attribute::NoInline);
+              }
+            }
+          }
         }
       }
 


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