[gcc/devel/autopar_devel] aarch64: Fix segfault in aarch64_expand_epilogue [PR95361]

[gcc/devel/autopar_devel] aarch64: Fix segfault in aarch64_expand_epilogue [PR95361]

[Giuliano Belinassi]

https://gcc.gnu.org/g:c3456584637c8f2bdaa6bd0bebd82ff9e606baed

commit c3456584637c8f2bdaa6bd0bebd82ff9e606baed
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu May 28 13:18:12 2020 +0100

    aarch64: Fix segfault in aarch64_expand_epilogue [PR95361]
    
    The stack frame for the function in the testcase consisted of two
    SVE save slots.  Both saves had been shrink-wrapped, but for different
    blocks, meaning that the stack allocation and deallocation were
    separate from the saves themselves.  Before emitting the deallocation,
    we tried to attach a REG_CFA_DEF_CFA note to the preceding instruction,
    to redefine the CFA in terms of the stack pointer.  But in this case
    there was no preceding instruction.
    
    This in practice only happens for SVE because:
    
    (a) We don't try to shrink-wrap wb_candidate* registers even when
        we've decided to treat them as normal saves and restores.
        I have a fix for that.
    
    (b) Even with (a) fixed, we're (almost?) guaranteed to emit
        a stack tie for frames that are 64k or larger, so we end
        up hanging the REG_CFA_DEF_CFA note on that instead.
    
    We should only need to redefine the CFA if it was previously
    defined in terms of the frame pointer.  In other cases the CFA
    should already be defined in terms of the stack pointer,
    so redefining it is unnecessary but usually harmless.
    
    2020-05-28  Richard Sandiford  <richard.sandiford@arm.com>
    
    gcc/
            PR testsuite/95361
            * config/aarch64/aarch64.c (aarch64_expand_epilogue): Assert that
            we have at least some CFI operations when using a frame pointer.
            Only redefine the CFA if we have CFI operations.
    
    gcc/testsuite/
            PR testsuite/95361
            * gcc.target/aarch64/sve/pr95361.c: New test.

Diff:
---
 gcc/config/aarch64/aarch64.c                   |  6 +++++-
 gcc/testsuite/gcc.target/aarch64/sve/pr95361.c | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 78db0a56323..cffb945d7dd 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -8180,7 +8180,11 @@ aarch64_expand_epilogue (bool for_sibcall)
   if (callee_adjust != 0)
     aarch64_pop_regs (reg1, reg2, callee_adjust, &cfi_ops);
 
-  if (callee_adjust != 0 || maybe_gt (initial_adjust, 65536))
+  /* If we have no register restore information, the CFA must have been
+     defined in terms of the stack pointer since the end of the prologue.  */
+  gcc_assert (cfi_ops || !frame_pointer_needed);
+
+  if (cfi_ops && (callee_adjust != 0 || maybe_gt (initial_adjust, 65536)))
     {
       /* Emit delayed restores and set the CFA to be SP + initial_adjust.  */
       insn = get_last_insn ();
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr95361.c b/gcc/testsuite/gcc.target/aarch64/sve/pr95361.c
new file mode 100644
index 00000000000..ce70d0d5cdf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/pr95361.c
@@ -0,0 +1,11 @@
+/* { dg-options "-O2" } */
+
+__SVInt8_t
+f (__SVInt8_t x, int y)
+{
+  if (y == 1)
+    asm volatile ("" ::: "z8");
+  if (y == 2)
+    asm volatile ("" ::: "z9");
+  return x;
+}