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

[Martin Sebor]

Attached is a patch that eliminates the unused stack frame
allocated by gcc 5 with -pg -mprofile-kernel on powepc64le
and brings the code into parity with previous gcc versions.

The patch doesn't do anything to change the emitted code
when -mprofile-kernel is used without -pg. Since the former
option isn't fully documented (as noted in pr 65372) it's
unclear what effect it should be expected to have without
-pg.

The patch was tested on {powerpc64,powerpc64le}-linux.

Martin

2015-03-13  Anton Blanchard  <an...@samba.org>

	PR target/63354
	* gcc/config/rs6000/linux64.h (ARGET_KEEP_LEAF_WHEN_PROFILED): Define.
	* cc/config/rs6000/rs6000.c (rs6000_keep_leaf_when_profiled). New
	function.

2015-03-13  Martin Sebor  <mse...@redhat.com>

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

diff --git a/gcc/config/rs6000/linux64.h b/gcc/config/rs6000/linux64.h
index 0879e7e..f51e892 100644
--- a/gcc/config/rs6000/linux64.h
+++ b/gcc/config/rs6000/linux64.h
@@ -59,6 +59,9 @@ extern int dot_symbols;
 
 #define TARGET_PROFILE_KERNEL profile_kernel
 
+#undef TARGET_KEEP_LEAF_WHEN_PROFILED
+#define TARGET_KEEP_LEAF_WHEN_PROFILED rs6000_keep_leaf_when_profiled
+
 #define TARGET_USES_LINUX64_OPT 1
 #ifdef HAVE_LD_LARGE_TOC
 #undef TARGET_CMODEL
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 3171eef..77731c56 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -24395,6 +24395,15 @@ rs6000_output_function_prologue (FILE *file,
   rs6000_pic_labelno++;
 }
 
+/* -mprofile-kernel code calls mcount before the function prolog,
+   so a profiled leaf function should stay a leaf function.  */
+
+static bool
+rs6000_keep_leaf_when_profiled (void)
+{
+  return TARGET_PROFILE_KERNEL;
+}
+
 /* 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/testsuite/gcc.target/powerpc/pr63354.c b/gcc/testsuite/gcc.target/powerpc/pr63354.c
new file mode 100644
index 0000000..dd6ad08
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr63354.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { 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," } } */