Re: [PATCH] pr 63354 - gcc -pg -mprofile-kernel creates unused stack frames on leaf functions on ppc64le

[Martin Sebor <msebor at redhat dot com>]

> I'm assuming that you mean a cross-compile (which is a stage1 without -werror).  If you look in the build output (I just repeated this on x86_64-darwin12 X powerpc-darwin9) you'll see:
>
> /GCC/gcc-trunk/gcc/config/rs6000/rs6000.c:24404:1: warning: ‘bool rs6000_keep_leaf_when_profiled()’ defined but not used [-Wunused-function]
>   rs6000_keep_leaf_when_profiled (void)
>   ^
>
> this becomes a bootstrap error at stage#2.  If you don't see that, then I have don't have the same patch applied as you :).

Yes, I meant a cross-compile. I don't have a Darwin environment
but I managed to reproduce it while building stage1 with -Werror
(after fixing a number of problems that cause the build to fail
earlier on). Thanks for your patience.

Attached is an updated patch with your suggested change (i.e.,
defining the TARGET_KEEP_LEAF_WHEN_PROFILED macro in rs6000.h
instead of linux64.h).

I tested the patch by building stage1 with -Werror for both
powerpc64-darwin9 and powerpc64-unknown-linux-gnu (both on
the latter target).

Martin

2015-03-24  Anton Blanchard  <anton@samba.org>

	PR target/63354
	* config/rs6000/rs6000.h (TARGET_KEEP_LEAF_WHEN_PROFILED): Define.
	* config/rs6000/rs6000.c (rs6000_keep_leaf_when_profiled): New
	function.

2015-03-24  Martin Sebor  <msebor@redhat.com>

	PR target/63354
	* gcc.target/powerpc/pr63354.c: New test.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 31b46ea..f1508b9 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -24397,6 +24397,23 @@ rs6000_output_function_prologue (FILE *file,
   rs6000_pic_labelno++;
 }
 
+/* -mprofile-kernel code calls mcount before the function prologue,
+   so a profiled leaf function should stay a leaf function.  */
+
+static bool
+rs6000_keep_leaf_when_profiled (void)
+{
+  switch (DEFAULT_ABI)
+    {
+      case ABI_AIX:
+      case ABI_ELFv2:
+       return TARGET_PROFILE_KERNEL;
+
+      default:
+       return true;
+    }
+}
+
 /* Non-zero if vmx regs are restored before the frame pop, zero if
    we restore after the pop when possible.  */
 #define ALWAYS_RESTORE_ALTIVEC_BEFORE_POP 0
diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index ef6bb2f..50394b0 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -703,6 +703,9 @@ extern unsigned char rs6000_recip_bits[];
 #define TARGET_CPU_CPP_BUILTINS() \
   rs6000_cpu_cpp_builtins (pfile)
 
+#undef TARGET_KEEP_LEAF_WHEN_PROFILED
+#define TARGET_KEEP_LEAF_WHEN_PROFILED rs6000_keep_leaf_when_profiled
+
 /* This is used by rs6000_cpu_cpp_builtins to indicate the byte order
    we're compiling for.  Some configurations may need to override it.  */
 #define RS6000_CPU_CPP_ENDIAN_BUILTINS()	\
diff --git a/gcc/testsuite/gcc.target/powerpc/pr63354.c b/gcc/testsuite/gcc.target/powerpc/pr63354.c
new file mode 100644
index 0000000..9e635cc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr63354.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target { powerpc64*-*-linux* } } } */
+/* { dg-options "-O2 -pg -mprofile-kernel" } */
+
+int foo (void)
+{
+  return 1;
+}
+
+/* { dg-final { scan-assembler "bl _mcount" } } */
+/* { dg-final { scan-assembler-not "(addi|stdu) 1," } } */