On 03/14/2015 08:34 AM, Segher Boessenkool wrote:
On Fri, Mar 13, 2015 at 03:54:57PM -0600, Martin Sebor wrote:
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.
-mprofile-kernel does nothing without profiling enabled. Maybe it
should just have been called -pk or something horrid like that.
The effect it should have is to do what the only user of the option
(the 64-bit PowerPC Linux kernel) wants. The effect it does have
is to make the 64-bit ABI more like the 32-bit ABI for mcount.
Thanks for the review and the clarification. FWIW, I mentioned
-pg because the reporter had noted that in prior versions of
GCC specifying -pg in addition to -mprofile-kernel wasn't
necessary to get the expected effect.
2015-03-13 Anton Blanchard <[email protected]>
PR target/63354
* gcc/config/rs6000/linux64.h (ARGET_KEEP_LEAF_WHEN_PROFILED): Define.
^ typo
* cc/config/rs6000/rs6000.c (rs6000_keep_leaf_when_profiled). New
^ typo ^ typo
It shouldn't have "gcc/" in the path names at all, actually.
Sorry, I must have mangled the ChangeLog sopmehow while copying
it from one terminal to another. I fixed it in the new patch
(attached) along with the other issues you pointed out.
I tested the changes in powerpc64*-linux-* native builds and on
an x86_64 host in a build for the powerpc-unknown-linux-gnu and
powerpc64-apple-darwin targets. Of these, the -mprofile-kernel
option is only accepted for powerpc64*-linux-* (which was also
confirmed by inspecting the sources) so I adjusted the test
target accordingly and kept the body of
rs6000_keep_leaf_when_profiled you suggested.
Martin
+/* -mprofile-kernel code calls mcount before the function prolog,
"prologue".
+ so a profiled leaf function should stay a leaf function. */
+
+static bool
+rs6000_keep_leaf_when_profiled (void)
+{
+ return TARGET_PROFILE_KERNEL;
+}
Something like
switch (DEFAULT_ABI)
{
case ABI_AIX:
case ABI_ELFv2:
return TARGET_PROFILE_KERNEL;
default:
return true;
}
although I'm not sure about Darwin here. More conservative is to
return false for anything untested, of course.
--- /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," } } */
Either you should run this only on AIX/ELFv2 ABIs, or you want to
test for "stwu" as well. Bare "1" does not work for all assemblers
(only Darwin again?)
Segher
2015-03-13 Anton Blanchard <[email protected]>
PR target/63354
* config/rs6000/linux64.h (TARGET_KEEP_LEAF_WHEN_PROFILED): Define.
* config/rs6000/rs6000.c (rs6000_keep_leaf_when_profiled): New
function.
2015-03-13 Martin Sebor <[email protected]>
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 31b46ea..9bad535 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/testsuite/gcc.target/powerpc/pr63354.c b/gcc/testsuite/gcc.target/powerpc/pr63354.c
new file mode 100644
index 0000000..d95f1eb
--- /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," } } */
