explow, aarch64: Fix force-Pmode-to-mem for ILP32 [PR97269]

This patch fixes a mode/rtx mismatch for ILP32 targets in:

	  mem = force_const_mem (ptr_mode, imm);

where imm can be Pmode rather than ptr_mode.

The patch uses convert_memory_address to convert the Pmode address
to ptr_mode before the call.  However, immediate addresses can in
general contain unspecs, and convert_memory_address wasn't set up
to handle those.

The patch therefore adds some generic unspec handling to
convert_memory_address_addr_space_1.  As the comment says, we can add
a target hook if this behaviour turns out to be wrong for some targets.
But I think what the patch does is a strict improvement over the status
quo: without it, we would try to force the unspec into a register,
but nevertheless wrap the result in a (const ...).  That in turn
would be invalid rtl and seems bound to generate an ICE later.

I tested the explow.c part using -fstack-protector with local hacks
to force SYMBOL_FORCE_TO_MEM for UNSPEC_SALT_ADDR.

Fixes c-c++-common/torture/pr57945.c and various other tests.

gcc/
	PR target/97269
	* explow.c (convert_memory_address_addr_space_1): Handle UNSPECs
	nested in CONSTs.
	* config/aarch64/aarch64.c (aarch64_expand_mov_immediate): Use
	convert_memory_address to convert symbolic immediates to ptr_mode
	before forcing them to memory.

1 files changed, 20 insertions, 0 deletions

diff --git a/gcc/explow.c b/gcc/explow.c
index c474869..b6da277 100644
--- a/gcc/explow.c
+++ b/gcc/explow.c
@@ -378,6 +378,26 @@ convert_memory_address_addr_space_1 (scalar_int_mode to_mode ATTRIBUTE_UNUSED,
 	}
       break;
 
+    case UNSPEC:
+      /* Assume that all UNSPECs in a constant address can be converted
+	 operand-by-operand.  We could add a target hook if some targets
+	 require different behavior.  */
+      if (in_const && GET_MODE (x) == from_mode)
+	{
+	  unsigned int n = XVECLEN (x, 0);
+	  rtvec v = gen_rtvec (n);
+	  for (unsigned int i = 0; i < n; ++i)
+	    {
+	      rtx op = XVECEXP (x, 0, i);
+	      if (GET_MODE (op) == from_mode)
+		op = convert_memory_address_addr_space_1 (to_mode, op, as,
+							  in_const, no_emit);
+	      RTVEC_ELT (v, i) = op;
+	    }
+	  return gen_rtx_UNSPEC (to_mode, v, XINT (x, 1));
+	}
+      break;
+
     default:
       break;
     }