Add cachegrind support for php-cgi warmups

[iluuu1994]

Cachegrind supports cg_annotate --diff, which makes it much easier to compare the performance of two patches.

[devnexen]

LGTM

[iluuu1994]

I had to make a small adjustment for when the cachegrind header is not available, which apparently is a thing.

[devnexen]

just my 2 cents, might be possible to check it only when valgrind detection is succesful (above) no ?

[iluuu1994]

Maybe. The configure.ac syntax is so confusing to me that I decided to just create a new if. 😅 If Peter prefers refactoring this, I'll go ahead.

[petk]

I totally agree. This Autoconf shell-mixed full-of-portability-concerns syntax is so horrible, that it's not something to keep for too long. Hopefully this will be replaced one day with CMake. Another syntax, but just few levels less horrible :D

[iluuu1994]

Thank you! 🙏 Thank you for all your work!

[petk]

For the configure.ac part this can be done to wrap it inside a single "if" check (this [no] and checking if it is not no, there is for a minor BC because once there was possible to pass a directory to --with-valgrind=DIR).

To check the Valgrind header, also CFLAGS need to be adjusted a bit because the Valgrind headers might need additional include flags. So this will work:

diff --git a/configure.ac b/configure.ac
index 3ba5703871..b7c3e2ce78 100644
--- a/configure.ac
+++ b/configure.ac
@@ -745,11 +745,16 @@ PHP_ARG_WITH([valgrind],
   [no],
   [no])
 
-AS_VAR_IF([PHP_VALGRIND], [no],,
-  [PKG_CHECK_MODULES([VALGRIND], [valgrind],
+AS_VAR_IF([PHP_VALGRIND], [no],, [
+  PKG_CHECK_MODULES([VALGRIND], [valgrind],
     [PHP_EVAL_INCLINE([$VALGRIND_CFLAGS])
       AC_DEFINE([HAVE_VALGRIND], [1],
-        [Define to 1 if Valgrind is enabled and supported.])])])
+        [Define to 1 if Valgrind is enabled and supported.])])
+  save_CFLAGS=$CFLAGS
+  CFLAGS="$CFLAGS $VALGRIND_CFLAGS"
+  AC_CHECK_HEADERS([valgrind/cachegrind.h])
+  CFLAGS=$save_CFLAGS
+])