Add -fdiagnostics-show-hotness

Summary:
I've recently added the ability for optimization remarks to include the
hotness of the corresponding code region.  This uses PGO and allows
filtering of the optimization remarks by relevance.  The idea was first
discussed here:
http://thread.gmane.org/gmane.comp.compilers.llvm.devel/98334

The general goal is to produce a YAML file with the remarks.  Then, an
external tool could dynamically filter these by hotness and perhaps by
other things.

That said it makes sense to also expose this at the more basic level
where we just include the hotness info with each optimization remark.
For example, in D22694, the clang flag was pretty useful to measure the
overhead of the additional analyses required to include hotness.
(Without the flag we don't even run the analyses.)

For the record, Hal has already expressed support for the idea of this
patch on IRC.

Differential Revision: https://reviews.llvm.org/D23284

llvm-svn: 281276

1 files changed, 45 insertions, 0 deletions

diff --git a/clang/test/Frontend/optimization-remark-with-hotness.c b/clang/test/Frontend/optimization-remark-with-hotness.c
new file mode 100644
index 00000000000..ab9f6a5ba0a
--- /dev/null
+++ b/clang/test/Frontend/optimization-remark-with-hotness.c
@@ -0,0 +1,45 @@
+// RUN: llvm-profdata merge \
+// RUN:     %S/Inputs/optimization-remark-with-hotness.proftext   \
+// RUN:     -o %t.profdata
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
+// RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -Rpass-analysis=inline -fdiagnostics-show-hotness -verify
+// The clang version of the previous test.
+// RUN: %clang -target x86_64-apple-macosx10.9 %s -o /dev/null \
+// RUN:     -fprofile-instr-use=%t.profdata -Rpass=inline \
+// RUN:     -Rpass-analysis=inline -fdiagnostics-show-hotness -Xclang -verify
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
+// RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -Rpass-analysis=inline 2>&1 | FileCheck -check-prefix=HOTNESS_OFF %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
+// RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -Rpass-analysis=inline -Rno-pass-with-hotness  2>&1 | FileCheck \
+// RUN:     -check-prefix=HOTNESS_OFF %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
+// RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
+// RUN:     -Rpass=inline -Rpass-analysis=inline -fdiagnostics-show-hotness  2>&1 \
+// RUN:     | FileCheck -check-prefix=NO_PGO %s
+
+int foo(int x, int y) __attribute__((always_inline));
+int foo(int x, int y) { return x + y; }
+
+int sum = 0;
+
+void bar(int x) {
+  // HOTNESS_OFF: foo inlined into bar
+  // HOTNESS_OFF-NOT: hotness:
+  // NO_PGO: '-fdiagnostics-show-hotness' requires profile-guided optimization information
+  // expected-remark@+2 {{foo should always be inlined (cost=always) (hotness: 30)}}
+  // expected-remark@+1 {{foo inlined into bar (hotness: 30)}}
+  sum += foo(x, x - 2);
+}
+
+int main(int argc, const char *argv[]) {
+  for (int i = 0; i < 30; i++)
+    // expected-remark@+1 {{bar should never be inlined}}
+    bar(argc);
+  return sum;
+}