[PATCH][explow] PR target/85173: validize memory before passing it on to target probe_stack

[Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>]

Hi all,

In this PR the expansion code emits an invalid memory address for the stack probe, which the backend fails to recognise.
The address is created explicitly in anti_adjust_stack_and_probe_stack_clash in explow.c and passed down to gen_probe_stack
without any validation in emit_stack_probe.

This patch fixes the ICE by calling validize_mem on the memory location before passing it down to the target.
Jakub pointed out that we also want to create valid addresses for the probe_stack_address case, so this patch
creates an expand operand and legitimizes it before passing it down to the probe_stack_address expander.

This patch passes bootstrap and testing on arm-none-linux-gnueabihf and aarch64-none-linux-gnu
and ppc64le-redhat-linux on gcc112 in the compile farm.

Is this ok for trunk?

Thanks,
Kyrill

P.S. Uros, the alpha probe_stack expander in alpha.md seems incompatible with the way the probe_stack name is
used in the midend. It accepts a const_int operand that is used as an offset from the stack pointer, rather than accepting
a full memory operand like other targets. Do you think it's better to rename the probe_stack pattern there to something
that doesn't conflict with the name the midend assumes?

2018-04-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    PR target/85173
    * explow.c (emit_stack_probe): Call validize_mem on memory location
    before passing it to gen_probe_stack.  Create address operand and
    legitimize it for the probe_stack_address case.

2018-04-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    PR target/85173
    * gcc.target/arm/pr85173.c: New test.

commit dc4e225eb394eaba8765425c0c7076c13d107580
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Tue Apr 3 16:46:15 2018 +0100

    [explow] PR target/85173: validize memory before passing it on to target probe_stack

diff --git a/gcc/explow.c b/gcc/explow.c
index 042e719..fb2b7ff 100644
--- a/gcc/explow.c
+++ b/gcc/explow.c
@@ -1626,18 +1626,25 @@ void
 emit_stack_probe (rtx address)
 {
   if (targetm.have_probe_stack_address ())
-    emit_insn (targetm.gen_probe_stack_address (address));
+    {
+      struct expand_operand ops[1];
+      insn_code icode = targetm.code_for_probe_stack_address;
+      create_address_operand (ops, address);
+      maybe_legitimize_operands (icode, 0, 1, ops);
+      expand_insn (icode, 1, ops);
+    }
   else
     {
       rtx memref = gen_rtx_MEM (word_mode, address);
 
       MEM_VOLATILE_P (memref) = 1;
+      memref = validize_mem (memref);
 
       /* See if we have an insn to probe the stack.  */
       if (targetm.have_probe_stack ())
-        emit_insn (targetm.gen_probe_stack (memref));
+	emit_insn (targetm.gen_probe_stack (memref));
       else
-        emit_move_insn (memref, const0_rtx);
+	emit_move_insn (memref, const0_rtx);
     }
 }
 
diff --git a/gcc/testsuite/gcc.target/arm/pr85173.c b/gcc/testsuite/gcc.target/arm/pr85173.c
new file mode 100644
index 0000000..36105c9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr85173.c
@@ -0,0 +1,20 @@
+/* PR target/85173.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-probe-interval=14" } */
+/* { dg-require-effective-target arm_thumb2_ok } */
+
+__attribute__((noinline, noclone)) void
+foo (char *p)
+{
+  asm volatile ("" : : "r" (p) : "memory");
+}
+
+/* Nonconstant alloca, small local frame.  */
+__attribute__((noinline, noclone)) void
+f5 (int x)
+{
+  char locals[128];
+  char *vla = __builtin_alloca (x);
+  foo (vla);
+}