Add function entry counts from sample profiles.

This patch uses the new function profile metadata "function_entry_count"
to annotate entry counts from sample profiles.

In a sampling profile, the total samples collected at the function entry
are an approximation for the number of times that function was invoked.

llvm-svn: 237265

3 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/SampleProfile.cpp b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
index 594a7beb2e3..3480cd49912 100644
--- a/llvm/lib/Transforms/Scalar/SampleProfile.cpp
+++ b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
@@ -580,6 +580,10 @@ void SampleProfileLoader::propagateWeights(Function &F) {
   bool Changed = true;
   unsigned i = 0;
 
+  // Add an entry count to the function using the samples gathered
+  // at the function entry.
+  F.setEntryCount(Samples->getHeadSamples());
+
   // Before propagation starts, build, for each block, a list of
   // unique predecessors and successors. This is necessary to handle
   // identical edges in multiway branches. Since we visit all blocks and all
diff --git a/llvm/test/Transforms/SampleProfile/Inputs/entry_counts.prof b/llvm/test/Transforms/SampleProfile/Inputs/entry_counts.prof
new file mode 100644
index 00000000000..5c2172b5a4d
--- /dev/null
+++ b/llvm/test/Transforms/SampleProfile/Inputs/entry_counts.prof
@@ -0,0 +1,3 @@
+empty:100:13293
+0: 0
+1: 100
diff --git a/llvm/test/Transforms/SampleProfile/entry_counts.ll b/llvm/test/Transforms/SampleProfile/entry_counts.ll
new file mode 100644
index 00000000000..bf66e693a9d
--- /dev/null
+++ b/llvm/test/Transforms/SampleProfile/entry_counts.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/entry_counts.prof -S | FileCheck %s
+
+; According to the profile, function empty() was called 13,293 times.
+; CHECK: {{.*}} = !{!"function_entry_count", i64 13293}
+
+define void @empty() {
+entry:
+  ret void, !dbg !9
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!6, !7}
+!llvm.ident = !{!8}
+
+!0 = !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.7.0 (trunk 237249) (llvm/trunk 237261)", isOptimized: false, runtimeVersion: 0, emissionKind: 2, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !DIFile(filename: "entry_counts.c", directory: "/usr/local/google/home/dnovillo/llvm/test/pgo")
+!2 = !{}
+!3 = !{!4}
+!4 = !DISubprogram(name: "empty", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, function: void ()* @empty, variables: !2)
+!5 = !DISubroutineType(types: !2)
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{!"clang version 3.7.0 (trunk 237249) (llvm/trunk 237261)"}
+!9 = !DILocation(line: 1, column: 15, scope: !4)