From a48847eea5f39c1f9fbe4255c9e892647f13f995 Mon Sep 17 00:00:00 2001 From: Luis Machado Date: Mon, 24 Aug 2015 12:33:21 -0300 Subject: [PATCH] Prevent GCC from folding inline test functions While doing some powerpc Linux tests on a ppc 476 board using GCC 5.2, i noticed inline-bt.exp, inline-cmds.exp and inline-locals.exp failing. FAIL: gdb.opt/inline-bt.exp: continue to bar (1) FAIL: gdb.opt/inline-bt.exp: backtrace from bar (1) FAIL: gdb.opt/inline-bt.exp: continue to bar (2) FAIL: gdb.opt/inline-bt.exp: backtrace from bar (2) FAIL: gdb.opt/inline-bt.exp: continue to bar (3) FAIL: gdb.opt/inline-bt.exp: backtrace from bar (3) FAIL: gdb.opt/inline-cmds.exp: continue to bar (1) FAIL: gdb.opt/inline-cmds.exp: backtrace from bar (1) FAIL: gdb.opt/inline-cmds.exp: continue to bar (2) FAIL: gdb.opt/inline-cmds.exp: backtrace from bar (2) FAIL: gdb.opt/inline-cmds.exp: continue to marker FAIL: gdb.opt/inline-cmds.exp: backtrace from marker FAIL: gdb.opt/inline-cmds.exp: step into finish marker FAIL: gdb.opt/inline-locals.exp: continue to bar (1) FAIL: gdb.opt/inline-locals.exp: continue to bar (2) FAIL: gdb.opt/inline-locals.exp: backtrace from bar (2) FAIL: gdb.opt/inline-locals.exp: continue to bar (3) FAIL: gdb.opt/inline-locals.exp: backtrace from bar (3) They failed because the breakpoint supposedly inserted at bar was actually inserted at noinline. (gdb) break inline-markers.c:20^M Breakpoint 2 at 0x1000079c: file gdb/testsuite/gdb.opt/inline-markers.c, line 20.^M (gdb) continue^M Continuing.^M ^M Breakpoint 2, noinline () at gdb/testsuite/gdb.opt/inline-markers.c:35^M 35 inlined_fn (); /* inlined */^M As we can see, line 20 is really inside bar, not noinline: 18 void bar(void) 19 { 20 x += y; /* set breakpoint 1 here */ 21 } Further investigation shows that this is really due to GCC 5's new ICF pass (-fipa-icf), now enabled by default at -O2, which folds bar and marker into noinline, where the call to inlined_fn was inlined. This breaks the testcase since it expects to stop at specific spots. I thought about two possible fixes for this issue. - Disable the ICF pass manually when building the binary (-fno-ipa-icf). This has the advantage of not having to touch the testcase sources themselves, but the disadvantage of having to add conditional blocks to test the GCC version. If we ever change GCC's default, we will have to adjust the conditional block again to match GCC's behavior. - Modify the testcase sources to make the identical functions unique. This solution doesn't touch the testcase itself, but changes the source code slightly in order to make bar, marker and inlined_fn unique. This causes GCC's ICF pass to ignore these functions and not fold them into a common identical function. I'm good with either of them, but i'm more inclined to go with the second one. The attached patch implements this by adding the new global variable z, set to 0, that gets added in different ways to marker and inlined_fn. Since it is 0, it doesn't affect any possible value checks that we may wish to do in the future (we currently only check for values changed by bar). Ok? ps: I also noticed GDB doesn't do a great job at stating that the breakpoint was actually inserted at a different source line than previously requested, so this sounds like a bug that should be fixed, if it is not just wrong DWARF information (did not investigate it further). gdb/testsuite/ChangeLog: 2015-08-24 Luis Machado * gdb.opt/inline-bt.c: New volatile global z. * gdb.opt/inline-cmds.c: Likewise. * gdb.opt/inline-locals.c: Likewise. * gdb.opt/inline-markers.c: New extern global z. (marker): Use z. (inline_fn): Likewise. --- gdb/testsuite/ChangeLog | 9 +++++++++ gdb/testsuite/gdb.opt/inline-bt.c | 1 + gdb/testsuite/gdb.opt/inline-cmds.c | 1 + gdb/testsuite/gdb.opt/inline-locals.c | 1 + gdb/testsuite/gdb.opt/inline-markers.c | 6 +++--- 5 files changed, 15 insertions(+), 3 deletions(-) diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index c3d5182d1e5..b788c0f8eca 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,12 @@ +2015-08-24 Luis Machado + + * gdb.opt/inline-bt.c: New volatile global z. + * gdb.opt/inline-cmds.c: Likewise. + * gdb.opt/inline-locals.c: Likewise. + * gdb.opt/inline-markers.c: New extern global z. + (marker): Use z. + (inline_fn): Likewise. + 2015-08-24 Pedro Alves * config/m32r-stub.exp: Remove file. diff --git a/gdb/testsuite/gdb.opt/inline-bt.c b/gdb/testsuite/gdb.opt/inline-bt.c index dc2bd45c37f..a47d16e6afd 100644 --- a/gdb/testsuite/gdb.opt/inline-bt.c +++ b/gdb/testsuite/gdb.opt/inline-bt.c @@ -23,6 +23,7 @@ #endif int x, y; +volatile int z = 0; volatile int result; void bar(void); diff --git a/gdb/testsuite/gdb.opt/inline-cmds.c b/gdb/testsuite/gdb.opt/inline-cmds.c index 9955720c912..cc43b57b689 100644 --- a/gdb/testsuite/gdb.opt/inline-cmds.c +++ b/gdb/testsuite/gdb.opt/inline-cmds.c @@ -23,6 +23,7 @@ #endif int x, y; +volatile int z = 0; volatile int result; void bar(void); diff --git a/gdb/testsuite/gdb.opt/inline-locals.c b/gdb/testsuite/gdb.opt/inline-locals.c index fc018bfa960..fa5cd137b11 100644 --- a/gdb/testsuite/gdb.opt/inline-locals.c +++ b/gdb/testsuite/gdb.opt/inline-locals.c @@ -23,6 +23,7 @@ #endif int x, y; +volatile int z = 0; volatile int result; volatile int *array_p; diff --git a/gdb/testsuite/gdb.opt/inline-markers.c b/gdb/testsuite/gdb.opt/inline-markers.c index 46c68ae9d8e..5d5503331d4 100644 --- a/gdb/testsuite/gdb.opt/inline-markers.c +++ b/gdb/testsuite/gdb.opt/inline-markers.c @@ -13,7 +13,7 @@ You should have received a copy of the GNU General Public License along with this program. If not, see . */ -extern int x, y; +extern int x, y, z; void bar(void) { @@ -22,12 +22,12 @@ void bar(void) void marker(void) { - x += y; /* set breakpoint 2 here */ + x += y - z; /* set breakpoint 2 here */ } inline void inlined_fn(void) { - x += y; + x += y + z; } void noinline(void) -- 2.30.2