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author | Jeff Law <law@redhat.com> | 2018-01-03 11:22:28 -0700 |
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committer | Jeff Law <law@gcc.gnu.org> | 2018-01-03 11:22:28 -0700 |
commit | 86aa0691c599e86e966bd1e81e95858a83d5e671 (patch) | |
tree | d956d13e907210786986b283e145f3e97ada7538 /gcc/explow.c | |
parent | e95e79b628438a978b14c9a0740e0bb8072477e0 (diff) | |
download | gcc-86aa0691c599e86e966bd1e81e95858a83d5e671.zip gcc-86aa0691c599e86e966bd1e81e95858a83d5e671.tar.gz gcc-86aa0691c599e86e966bd1e81e95858a83d5e671.tar.bz2 |
re PR middle-end/83654 (-fstack-clash-protection probes below the stack pointer for VLA with constant size)
PR middle-end/83654
* explow.c (anti_adjust_stack_and_probe_stack_clash): Test a
non-constant residual for zero at runtime and avoid probing in
that case. Reorganize code for trailing problem to mirror handling
of the residual.
PR middle-end/83654
* gcc.target/i386/stack-check-18.c: New test.
* gcc.target/i386/stack-check-19.c: New test.
From-SVN: r256182
Diffstat (limited to 'gcc/explow.c')
-rw-r--r-- | gcc/explow.c | 42 |
1 files changed, 25 insertions, 17 deletions
diff --git a/gcc/explow.c b/gcc/explow.c index b6c5660..042e719 100644 --- a/gcc/explow.c +++ b/gcc/explow.c @@ -1997,11 +1997,27 @@ anti_adjust_stack_and_probe_stack_clash (rtx size) if (residual != CONST0_RTX (Pmode)) { + rtx label = NULL_RTX; + /* RESIDUAL could be zero at runtime and in that case *sp could + hold live data. Furthermore, we do not want to probe into the + red zone. + + Go ahead and just guard the probe at *sp on RESIDUAL != 0 at + runtime if RESIDUAL is not a compile time constant. */ + if (!CONST_INT_P (residual)) + { + label = gen_label_rtx (); + emit_cmp_and_jump_insns (residual, CONST0_RTX (GET_MODE (residual)), + EQ, NULL_RTX, Pmode, 1, label); + } + rtx x = force_reg (Pmode, plus_constant (Pmode, residual, -GET_MODE_SIZE (word_mode))); anti_adjust_stack (residual); emit_stack_probe (gen_rtx_PLUS (Pmode, stack_pointer_rtx, x)); emit_insn (gen_blockage ()); + if (!CONST_INT_P (residual)) + emit_label (label); } /* Some targets make optimistic assumptions in their prologues about @@ -2014,28 +2030,20 @@ anti_adjust_stack_and_probe_stack_clash (rtx size) live data. Furthermore, we don't want to probe into the red zone. - Go ahead and just guard a probe at *sp on SIZE != 0 at runtime + Go ahead and just guard the probe at *sp on SIZE != 0 at runtime if SIZE is not a compile time constant. */ - - /* Ideally we would just probe at *sp. However, if SIZE is not - a compile-time constant, but is zero at runtime, then *sp - might hold live data. So probe at *sp if we know that - an allocation was made, otherwise probe into the red zone - which is obviously undesirable. */ - if (CONST_INT_P (size)) - { - emit_stack_probe (stack_pointer_rtx); - emit_insn (gen_blockage ()); - } - else + rtx label = NULL_RTX; + if (!CONST_INT_P (size)) { - rtx label = gen_label_rtx (); + label = gen_label_rtx (); emit_cmp_and_jump_insns (size, CONST0_RTX (GET_MODE (size)), EQ, NULL_RTX, Pmode, 1, label); - emit_stack_probe (stack_pointer_rtx); - emit_insn (gen_blockage ()); - emit_label (label); } + + emit_stack_probe (stack_pointer_rtx); + emit_insn (gen_blockage ()); + if (!CONST_INT_P (size)) + emit_label (label); } } |