[PATCH, alpha]: Fix PR 22093, Unaligned access to HI values causes unrecognizable insn error

[Uros Bizjak]

Hello!

The problem is, that we expand unaligned access through:

  [(set (match_operand:DI 3 "register_operand" "")
	(mem:DI (and:DI (match_operand:DI 0 "address_operand" "")
			(const_int -8))))
   (set (match_operand:DI 2 "register_operand" "")
	(plus:DI (match_dup 0) (const_int 1)))

where the first operand of plus RTX does not satisfy corresponding
insn predicate:

(define_insn "*adddi_internal"
  [(set (match_operand:DI 0 "register_operand" "=r,r,r")
	(plus:DI (match_operand:DI 1 "register_operand" "%r,r,r")
		 (match_operand:DI 2 "add_operand" "r,K,L")))]

So, we should force the operand of plus RTX into register.

Fixed gcc produces:

        lda $2,2($31)
        lda $1,x
        lda $4,7($1)
        ldq_u $3,6($1)
        inswl $2,$4,$2
        mskwl $3,$4,$3
        bis $2,$3,$2
        stq_u $2,6($1)
        ret $31,($26),1

which is just what we expect.

Tested on alphaev68-pc-linux-gnu and by eyeballing generated code with #define
-------------- next part --------------
Index: config/alpha/alpha.md
===================================================================
--- config/alpha/alpha.md	(revision 152321)
+++ config/alpha/alpha.md	(working copy)
@@ -5861,7 +5861,7 @@
 	(mem:DI (and:DI (match_operand:DI 0 "address_operand" "")
 			(const_int -8))))
    (set (match_operand:DI 2 "register_operand" "")
-	(plus:DI (match_dup 0) (const_int 1)))
+	(plus:DI (match_dup 5) (const_int 1)))
    (set (match_dup 3)
 	(and:DI (not:DI (ashift:DI
 			  (const_int 65535)
@@ -5876,7 +5876,7 @@
    (set (mem:DI (and:DI (match_dup 0) (const_int -8)))
 	(match_dup 4))]
   "WORDS_BIG_ENDIAN"
-  "")
+  "operands[5] = force_reg (DImode, operands[0]);")
 

 ;; Here are the define_expand's for QI and HI moves that use the above
 ;; patterns.  We have the normal sets, plus the ones that need scratch
Index: testsuite/gcc.target/alpha/pr22093.c
===================================================================
--- testsuite/gcc.target/alpha/pr22093.c	(revision 0)
+++ testsuite/gcc.target/alpha/pr22093.c	(revision 152322)
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct shared_ptr_struct
+{
+  unsigned long phase : 48;
+  unsigned thread : 16;
+  void *addr;
+} x;
+
+void foo (void)
+{
+   x.thread = 2;
+}