[InstrProf] Test that entry coverage counts accumulate

[ellishg]

Entry coverage (-pgo-function-entry-coverage) and block covearge (-pgo-block-coverage) can be useful to reduce the size overhead of instrumented builds, and the profiles they generate can even be used in PGO builds.

When merging raw profiles with coverage, we accumulate their values as if they were counts and llvm-profdata considers a value to be "covered" if it's larger than zero.

llvm-project/llvm/lib/ProfileData/InstrProf.cpp

Lines 841 to 842 in acdb4cd

	uint64_t Value =
	SaturatingMultiplyAdd(Other.Counts[I], Weight, Counts[I], &Overflowed);

This is technically different than accumulating counts, but it can help discriminate cold functions from hot functions when the number of raw profiles is large.

See #75425 (comment) for discussion.

[llvmbot]

@llvm/pr-subscribers-pgo

Author: Ellis Hoag (ellishg)

Changes

Entry coverage (-pgo-function-entry-coverage) and block covearge (-pgo-block-coverage) can be useful to reduce the size overhead of instrumented builds, and the profiles they generate can even be used in PGO builds.

When merging raw profiles with coverage, we accumulate their values as if they were counts and llvm-profdata considers a value to be "covered" if it's larger than zero.

llvm-project/llvm/lib/ProfileData/InstrProf.cpp

Lines 841 to 842 in acdb4cd

	uint64_t Value =
	SaturatingMultiplyAdd(Other.Counts[I], Weight, Counts[I], &Overflowed);

This is technically different than accumulating counts, but it can help discriminate cold functions from hot functions when the number of raw profiles is large.

See #75425 (comment) for discussion.

---

Full diff: https://github.com/llvm/llvm-project/pull/81806.diff

2 Files Affected:

• (modified) compiler-rt/test/profile/instrprof-block-coverage.c (+5)
• (modified) compiler-rt/test/profile/instrprof-entry-coverage.c (+11)

diff --git a/compiler-rt/test/profile/instrprof-block-coverage.c b/compiler-rt/test/profile/instrprof-block-coverage.c
index 4f1e77810ab5fd..829d5af8dc3f9e 100644
--- a/compiler-rt/test/profile/instrprof-block-coverage.c
+++ b/compiler-rt/test/profile/instrprof-block-coverage.c
@@ -5,6 +5,9 @@
 // RUN: %clang_profuse=%t.profdata -mllvm -pgo-verify-bfi -o - -S -emit-llvm %s 2>%t.errs | FileCheck %s --implicit-check-not="!prof"
 // RUN: FileCheck %s < %t.errs --allow-empty --check-prefix=CHECK-ERROR
 
+// RUN: llvm-profdata merge -o %t2.profdata %t1.profraw %t1.profraw %t2.profraw %t2.profraw
+// RUN: llvm-profdata show %t2.profdata | FileCheck %s --check-prefix=COUNTS
+
 #include <stdlib.h>
 
 // CHECK: @foo({{.*}})
@@ -45,3 +48,5 @@ int main(int argc, char *argv[]) {
 // CHECK-DAG: ![[PROF2]] = !{!"branch_weights", i32 0, i32 1}
 
 // CHECK-ERROR-NOT: warning: {{.*}}: Found inconsistent block coverage
+
+// COUNTS: Maximum function count: 4
diff --git a/compiler-rt/test/profile/instrprof-entry-coverage.c b/compiler-rt/test/profile/instrprof-entry-coverage.c
index 99ec38b3e2a6c9..1c6816ba01964b 100644
--- a/compiler-rt/test/profile/instrprof-entry-coverage.c
+++ b/compiler-rt/test/profile/instrprof-entry-coverage.c
@@ -3,10 +3,19 @@
 // RUN: llvm-profdata merge -o %t.profdata %t.profraw
 // RUN: llvm-profdata show --covered %t.profdata | FileCheck %s --implicit-check-not goo
 
+// We deliberately merge the raw profile twice to test that internal counts can
+// grow larger than one. Technically, accumulating coverage values is different
+// than accumulating counts, but this helps discriminate cold functions from hot
+// functions when the number of raw profiles is large.
+// RUN: llvm-profdata merge -o %t2.profdata %t.profraw %t.profraw
+// RUN: llvm-profdata show %t2.profdata | FileCheck %s --check-prefix=COUNTS
+
 // RUN: %clang_cspgogen -O1 -mllvm -pgo-function-entry-coverage %s -o %t.cs.out
 // RUN: env LLVM_PROFILE_FILE=%t.csprofraw %run %t.cs.out
 // RUN: llvm-profdata merge -o %t.csprofdata %t.csprofraw
 // RUN: llvm-profdata show --covered %t.csprofdata --showcs | FileCheck %s --implicit-check-not goo
+// RUN: llvm-profdata merge -o %t2.csprofdata %t.csprofraw %t.csprofraw
+// RUN: llvm-profdata show --showcs %t2.csprofdata | FileCheck %s --check-prefix=COUNTS
 
 void markUsed(int a) {
   volatile int g;
@@ -26,3 +35,5 @@ int main(int argc, char *argv[]) {
 // CHECK-DAG: main
 // CHECK-DAG: foo
 // CHECK-DAG: bar
+
+// COUNTS: Maximum function count: 2