arm: Fix ICE with -fstack-protector -mpure-code [PR98998]

The vla15.C testcase ICEs with
-mcpu=cortex-m1 -mpure-code -fstack-protector -mthumb
as what force_const_mem returns (a SYMBOL_REF) is not a valid
memory address.
Previously the code was moving the address of the force_const_mem
into a register rather than the content of that MEM, so that instruction
must have been supported and loading from a MEM with a single REG base ought
to be valid too.

2021-02-19  Jakub Jelinek  <jakub@redhat.com>

	PR target/98998
	* config/arm/arm.md (*stack_protect_combined_set_insn,
	*stack_protect_combined_test_insn): If force_const_mem result
	is not valid general operand, force its address into the destination
	register first.

	* gcc.target/arm/pure-code/pr98998.c: New test.

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 3e441f9..45a471a 100644 (file)
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -9216,6 +9216,11 @@
       else
        {
          rtx mem = force_const_mem (SImode, operands[1]);
+         if (!general_operand (mem, SImode))
+           {
+             emit_move_insn (operands[2], XEXP (mem, 0));
+             mem = replace_equiv_address (mem, operands[2], false);
+           }
          emit_move_insn (operands[2], mem);
        }
     }
@@ -9299,6 +9304,11 @@
       else
        {
          rtx mem = force_const_mem (SImode, operands[1]);
+         if (!general_operand (mem, SImode))
+           {
+             emit_move_insn (operands[3], XEXP (mem, 0));
+             mem = replace_equiv_address (mem, operands[3], false);
+           }
          emit_move_insn (operands[3], mem);
        }
     }

diff --git a/gcc/testsuite/gcc.target/arm/pure-code/pr98998.c b/gcc/testsuite/gcc.target/arm/pure-code/pr98998.c
new file mode 100644 (file)
index 0000000..9d7b0b2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pure-code/pr98998.c
@@ -0,0 +1,20 @@
+/* PR target/98998 */
+/* { dg-do compile { target fstack_protector } } */
+/* { dg-options "-mpure-code -fstack-protector" } */
+
+void *volatile p;
+
+int
+main ()
+{
+  int n = 0;
+ lab:;
+  int x[n % 1000 + 1];
+  x[0] = 1;
+  x[n % 1000] = 2;
+  p = x;
+  n++;
+  if (n < 1000000)
+    goto lab;
+  return 0;
+}