Improve the fix for PR64242. Various optimizations can change a memory
reference
into a frame access. Given there are multiple virtual frame pointers which may
be replaced by multiple hard frame pointers, there are no checks for writes to
the
various frame pointers. So updates to a frame pointer tends to generate
incorrect
code. Improve the previous fix to also add clobbers of several frame pointers
and
add a scheduling barrier. This should work in most cases until GCC supports a
generic "don't optimize across this instruction" feature.
Bootstrap OK. Testcase passes on AArch64 and x86-64. Inspected x86, Arm,
Thumb-1 and Thumb-2 assembler which looks correct.
ChangeLog:
2018-12-07 Wilco Dijkstra <wdijk...@arm.com>
gcc/
PR middle-end/64242
* builtins.c (expand_builtin_longjmp): Add frame clobbers and schedule
block.
(expand_builtin_nonlocal_goto): Likewise.
testsuite/
PR middle-end/64242
* gcc.c-torture/execute/pr64242.c: Update test.
--
diff --git a/gcc/builtins.c b/gcc/builtins.c
index
3f32754c4d35fc34af7c53156d2a356f69a94a8f..3463ffb153914a58e5baa3896a244842a28eef09
100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -1137,15 +1137,20 @@ expand_builtin_longjmp (rtx buf_addr, rtx value)
emit_insn (targetm.gen_nonlocal_goto (value, lab, stack, fp));
else
{
- lab = copy_to_reg (lab);
-
emit_clobber (gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (VOIDmode)));
emit_clobber (gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx));
+ lab = copy_to_reg (lab);
+
/* Restore the frame pointer and stack pointer. We must use a
temporary since the setjmp buffer may be a local. */
fp = copy_to_reg (fp);
emit_stack_restore (SAVE_NONLOCAL, stack);
+
+ /* Ensure the frame pointer move is not optimized. */
+ emit_insn (gen_blockage ());
+ emit_clobber (hard_frame_pointer_rtx);
+ emit_clobber (frame_pointer_rtx);
emit_move_insn (hard_frame_pointer_rtx, fp);
emit_use (hard_frame_pointer_rtx);
@@ -1284,15 +1289,20 @@ expand_builtin_nonlocal_goto (tree exp)
emit_insn (targetm.gen_nonlocal_goto (const0_rtx, r_label, r_sp, r_fp));
else
{
- r_label = copy_to_reg (r_label);
-
emit_clobber (gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (VOIDmode)));
emit_clobber (gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx));
+ r_label = copy_to_reg (r_label);
+
/* Restore the frame pointer and stack pointer. We must use a
temporary since the setjmp buffer may be a local. */
r_fp = copy_to_reg (r_fp);
emit_stack_restore (SAVE_NONLOCAL, r_sp);
+
+ /* Ensure the frame pointer move is not optimized. */
+ emit_insn (gen_blockage ());
+ emit_clobber (hard_frame_pointer_rtx);
+ emit_clobber (frame_pointer_rtx);
emit_move_insn (hard_frame_pointer_rtx, r_fp);
/* USE of hard_frame_pointer_rtx added for consistency;
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr64242.c
b/gcc/testsuite/gcc.c-torture/execute/pr64242.c
index
46a7b23d28d71604d141281c21fb0b77849b1b0d..e6139ede3f34d587ac53d04e286e5d75fd2ca76c
100644
--- a/gcc/testsuite/gcc.c-torture/execute/pr64242.c
+++ b/gcc/testsuite/gcc.c-torture/execute/pr64242.c
@@ -5,46 +5,31 @@ extern void abort (void);
__attribute ((noinline)) void
broken_longjmp (void *p)
{
- void *buf[5];
+ void *buf[32];
__builtin_memcpy (buf, p, 5 * sizeof (void*));
/* Corrupts stack pointer... */
__builtin_longjmp (buf, 1);
}
-__attribute ((noipa)) __UINTPTR_TYPE__
-foo (void *p)
-{
- return (__UINTPTR_TYPE__) p;
-}
-
-__attribute ((noipa)) void
-bar (void *p)
-{
- asm volatile ("" : : "r" (p));
-}
-
volatile int x = 0;
-void *volatile p;
-void *volatile q;
+char *volatile p;
+char *volatile q;
int
main ()
{
void *buf[5];
- struct __attribute__((aligned (32))) S { int a[4]; } s;
- bar (&s);
p = __builtin_alloca (x);
+ q = __builtin_alloca (x);
if (!__builtin_setjmp (buf))
broken_longjmp (buf);
+ /* Compute expected next alloca offset - some targets don't align properly
+ and allocate too much. */
+ p = q + (q - p);
+
/* Fails if stack pointer corrupted. */
- q = __builtin_alloca (x);
- if (foo (p) < foo (q))
- {
- if (foo (q) - foo (p) >= 1024)
- abort ();
- }
- else if (foo (p) - foo (q) >= 1024)
+ if (p != __builtin_alloca (x))
abort ();
return 0;
