tcg-arm: Remove restriction on qemu_ld output register

The main intent of the patch is to allow the tlb addend register
to be changed, without tying that change to the constraint.  But
the most common side-effect seems to be to enable usage of ldrd
with the r0,r1 pair.
Signed-off-by: NRichard Henderson <rth@twiddle.net>

tcg/arm/tcg-target.c

@@ -181,15 +181,6 @@ static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str)
         tcg_regset_reset_reg(ct->u.regs, TCG_REG_R1);
         tcg_regset_reset_reg(ct->u.regs, TCG_REG_R2);
         tcg_regset_reset_reg(ct->u.regs, TCG_REG_R14);
-#endif
-        break;
-    case 'L':
-        ct->ct |= TCG_CT_REG;
-        tcg_regset_set32(ct->u.regs, 0, (1 << TCG_TARGET_NB_REGS) - 1);
-#ifdef CONFIG_SOFTMMU
-        /* r1 is still needed to load data_reg or data_reg2,
-           so don't use it. */
-        tcg_regset_reset_reg(ct->u.regs, TCG_REG_R1);
 #endif
         break;
 
@@ -1314,8 +1305,17 @@ static void tcg_out_qemu_ld_slow_path(TCGContext *s, TCGLabelQemuLdst *lb)
         tcg_out_mov_reg(s, COND_AL, data_reg, TCG_REG_R0);
         break;
     case 3:
-        tcg_out_mov_reg(s, COND_AL, data_reg, TCG_REG_R0);
-        tcg_out_mov_reg(s, COND_AL, data_reg2, TCG_REG_R1);
+        if (data_reg != TCG_REG_R1) {
+            tcg_out_mov_reg(s, COND_AL, data_reg, TCG_REG_R0);
+            tcg_out_mov_reg(s, COND_AL, data_reg2, TCG_REG_R1);
+        } else if (data_reg2 != TCG_REG_R0) {
+            tcg_out_mov_reg(s, COND_AL, data_reg2, TCG_REG_R1);
+            tcg_out_mov_reg(s, COND_AL, data_reg, TCG_REG_R0);
+        } else {
+            tcg_out_mov_reg(s, COND_AL, TCG_REG_TMP, TCG_REG_R0);
+            tcg_out_mov_reg(s, COND_AL, data_reg2, TCG_REG_R1);
+            tcg_out_mov_reg(s, COND_AL, data_reg, TCG_REG_TMP);
+        }
         break;
     }
 
@@ -1420,17 +1420,27 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg *args, int opc)
         }
         break;
     case 3:
-        if (bswap) {
-            tcg_out_ld32_rwb(s, COND_AL, data_reg2, addend, addr_reg);
-            tcg_out_ld32_12(s, COND_AL, data_reg, addend, 4);
-            tcg_out_bswap32(s, COND_AL, data_reg2, data_reg2);
-            tcg_out_bswap32(s, COND_AL, data_reg, data_reg);
-        } else if (use_armv6_instructions
-                   && (data_reg & 1) == 0 && data_reg2 == data_reg + 1) {
-            tcg_out_ldrd_r(s, COND_AL, data_reg, addr_reg, addend);
-        } else {
-            tcg_out_ld32_rwb(s, COND_AL, data_reg, addend, addr_reg);
-            tcg_out_ld32_12(s, COND_AL, data_reg2, addend, 4);
+        {
+            /* Be careful not to modify data_reg and data_reg2
+               for the slow path below.  */
+            TCGReg dl = (bswap ? data_reg2 : data_reg);
+            TCGReg dh = (bswap ? data_reg : data_reg2);
+
+            if (use_armv6_instructions && (dl & 1) == 0 && dh == dl + 1) {
+                tcg_out_ldrd_r(s, COND_AL, dl, addr_reg, addend);
+            } else if (dl != addend) {
+                tcg_out_ld32_rwb(s, COND_AL, dl, addend, addr_reg);
+                tcg_out_ld32_12(s, COND_AL, dh, addend, 4);
+            } else {
+                tcg_out_dat_reg(s, COND_AL, ARITH_ADD, TCG_REG_TMP,
+                                addend, addr_reg, SHIFT_IMM_LSL(0));
+                tcg_out_ld32_12(s, COND_AL, dl, TCG_REG_TMP, 0);
+                tcg_out_ld32_12(s, COND_AL, dh, TCG_REG_TMP, 4);
+            }
+            if (bswap) {
+                tcg_out_bswap32(s, COND_AL, dh, dh);
+                tcg_out_bswap32(s, COND_AL, dl, dl);
+            }
         }
         break;
     }
@@ -2025,7 +2035,7 @@ static const TCGTargetOpDef arm_op_defs[] = {
     { INDEX_op_qemu_ld16u, { "r", "l" } },
     { INDEX_op_qemu_ld16s, { "r", "l" } },
     { INDEX_op_qemu_ld32, { "r", "l" } },
-    { INDEX_op_qemu_ld64, { "L", "L", "l" } },
+    { INDEX_op_qemu_ld64, { "r", "r", "l" } },
 
     { INDEX_op_qemu_st8, { "s", "s" } },
     { INDEX_op_qemu_st16, { "s", "s" } },
@@ -2037,7 +2047,7 @@ static const TCGTargetOpDef arm_op_defs[] = {
     { INDEX_op_qemu_ld16u, { "r", "l", "l" } },
     { INDEX_op_qemu_ld16s, { "r", "l", "l" } },
     { INDEX_op_qemu_ld32, { "r", "l", "l" } },
-    { INDEX_op_qemu_ld64, { "L", "L", "l", "l" } },
+    { INDEX_op_qemu_ld64, { "r", "r", "l", "l" } },
 
     { INDEX_op_qemu_st8, { "s", "s", "s" } },
     { INDEX_op_qemu_st16, { "s", "s", "s" } },