tcg/ppc: Use atom_and_align_for_opc

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/ppc/tcg-target.c.inc

@@ -2015,6 +2015,7 @@ static bool tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *lb)
 typedef struct {
     TCGReg base;
     TCGReg index;
+    TCGAtomAlign aa;
 } HostAddress;
 
 bool tcg_target_has_memory_bswap(MemOp memop)
@@ -2034,7 +2035,23 @@ static TCGLabelQemuLdst *prepare_host_addr(TCGContext *s, HostAddress *h,
 {
     TCGLabelQemuLdst *ldst = NULL;
     MemOp opc = get_memop(oi);
-    unsigned a_bits = get_alignment_bits(opc);
+    MemOp a_bits;
+
+    /*
+     * Book II, Section 1.4, Single-Copy Atomicity, specifies:
+     *
+     * Before 3.0, "An access that is not atomic is performed as a set of
+     * smaller disjoint atomic accesses. In general, the number and alignment
+     * of these accesses are implementation-dependent."  Thus MO_ATOM_IFALIGN.
+     *
+     * As of 3.0, "the non-atomic access is performed as described in
+     * the corresponding list", which matches MO_ATOM_SUBALIGN.
+     */
+    h->aa = atom_and_align_for_opc(s, opc,
+                                   have_isa_3_00 ? MO_ATOM_SUBALIGN
+                                                 : MO_ATOM_IFALIGN,
+                                   false);
+    a_bits = h->aa.align;
 
 #ifdef CONFIG_SOFTMMU
     int mem_index = get_mmuidx(oi);