[PATCH] D31202: Clang change: Do not inline hot callsites for samplepgo in thinlto compile phase.

[Dehao Chen via Phabricator via cfe-commits]

danielcdh created this revision.
Herald added subscribers: Prazek, mehdi_amini.

Because SamplePGO passes will be invoked twice in ThinLTO build: once at compile phase, the other at backend. We want to make sure the IR at the 2nd phase matches the hot part in pro
file, thus we do not want to inline hot callsites in the first phase.


https://reviews.llvm.org/D31202

Files:
  lib/CodeGen/BackendUtil.cpp
  test/CodeGen/Inputs/pgo-sample-thinlto-summary.prof
  test/CodeGen/pgo-sample-thinlto-summary.c


Index: test/CodeGen/pgo-sample-thinlto-summary.c
===================================================================
--- /dev/null
+++ test/CodeGen/pgo-sample-thinlto-summary.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=INLINE
+// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=NOINLINE
+// Checks if hot call is inlined by normal compile, but not inlined by
+// thinlto compile.
+
+int baz(int);
+int g;
+
+void foo(int n) {
+  for (int i = 0; i < n; i++)
+    g += baz(i);
+}
+
+// INLINE-NOT: call{{.*}}foo
+// NOINLINE: call{{.*}}foo
+void bar(int n) {
+  for (int i = 0; i < n; i++)
+    foo(i);
+}
Index: test/CodeGen/Inputs/pgo-sample-thinlto-summary.prof
===================================================================
--- /dev/null
+++ test/CodeGen/Inputs/pgo-sample-thinlto-summary.prof
@@ -0,0 +1,2 @@
+bar:100:100
+ 2: 2000 foo:2000
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -318,8 +318,13 @@
                                      !CodeGenOpts.DisableLifetimeMarkers);
     PMBuilder.Inliner = createAlwaysInlinerLegacyPass(InsertLifetimeIntrinsics);
   } else {
+    // We do not want to inline hot callsites for SamplePGO module-summary build
+    // because profile annotation will happen again in ThinLTO backend, and we
+    // want the IR of the hot path to match the profile.
     PMBuilder.Inliner = createFunctionInliningPass(
-        CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize);
+        CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize,
+        (!CodeGenOpts.SampleProfileFile.empty() &&
+         CodeGenOpts.EmitSummaryIndex));
   }
 
   PMBuilder.OptLevel = CodeGenOpts.OptimizationLevel;


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