tcg/tci: Restrict TCG_TARGET_NB_REGS to 16

As noted in several comments, 8 regs is not enough for 32-bit
to perform calls, as currently implemented.  Shortly, we will
rearrange the encoding which will make 32 regs impossible.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/tci/tcg-target.c.inc

@@ -187,7 +187,6 @@ static const int tcg_target_reg_alloc_order[] = {
     TCG_REG_R5,
     TCG_REG_R6,
     TCG_REG_R7,
-#if TCG_TARGET_NB_REGS >= 16
     TCG_REG_R8,
     TCG_REG_R9,
     TCG_REG_R10,
@@ -196,7 +195,6 @@ static const int tcg_target_reg_alloc_order[] = {
     TCG_REG_R13,
     TCG_REG_R14,
     TCG_REG_R15,
-#endif
 };
 
 #if MAX_OPC_PARAM_IARGS != 6
@@ -216,15 +214,11 @@ static const int tcg_target_call_iarg_regs[] = {
 #if TCG_TARGET_REG_BITS == 32
     /* 32 bit hosts need 2 * MAX_OPC_PARAM_IARGS registers. */
     TCG_REG_R7,
-#if TCG_TARGET_NB_REGS >= 16
     TCG_REG_R8,
     TCG_REG_R9,
     TCG_REG_R10,
     TCG_REG_R11,
     TCG_REG_R12,
-#else
-# error Too few input registers available
-#endif
 #endif
 };
 
@@ -245,7 +239,6 @@ static const char *const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
     "r05",
     "r06",
     "r07",
-#if TCG_TARGET_NB_REGS >= 16
     "r08",
     "r09",
     "r10",
@@ -254,25 +247,6 @@ static const char *const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
     "r13",
     "r14",
     "r15",
-#if TCG_TARGET_NB_REGS >= 32
-    "r16",
-    "r17",
-    "r18",
-    "r19",
-    "r20",
-    "r21",
-    "r22",
-    "r23",
-    "r24",
-    "r25",
-    "r26",
-    "r27",
-    "r28",
-    "r29",
-    "r30",
-    "r31"
-#endif
-#endif
 };
 #endif
 

tcg/tci/tcg-target.h

@@ -133,11 +133,8 @@
 #define TCG_TARGET_HAS_mulu2_i32        1
 #endif /* TCG_TARGET_REG_BITS == 64 */
 
-/* Number of registers available.
-   For 32 bit hosts, we need more than 8 registers (call arguments). */
-/* #define TCG_TARGET_NB_REGS 8 */
+/* Number of registers available. */
 #define TCG_TARGET_NB_REGS 16
-/* #define TCG_TARGET_NB_REGS 32 */
 
 /* List of registers which are used by TCG. */
 typedef enum {
@@ -149,7 +146,6 @@ typedef enum {
     TCG_REG_R5,
     TCG_REG_R6,
     TCG_REG_R7,
-#if TCG_TARGET_NB_REGS >= 16
     TCG_REG_R8,
     TCG_REG_R9,
     TCG_REG_R10,
@@ -158,33 +154,15 @@ typedef enum {
     TCG_REG_R13,
     TCG_REG_R14,
     TCG_REG_R15,
-#if TCG_TARGET_NB_REGS >= 32
-    TCG_REG_R16,
-    TCG_REG_R17,
-    TCG_REG_R18,
-    TCG_REG_R19,
-    TCG_REG_R20,
-    TCG_REG_R21,
-    TCG_REG_R22,
-    TCG_REG_R23,
-    TCG_REG_R24,
-    TCG_REG_R25,
-    TCG_REG_R26,
-    TCG_REG_R27,
-    TCG_REG_R28,
-    TCG_REG_R29,
-    TCG_REG_R30,
-    TCG_REG_R31,
-#endif
-#endif
+
+    TCG_AREG0 = TCG_REG_R14,
+    TCG_REG_CALL_STACK = TCG_REG_R15,
+
     /* Special value UINT8_MAX is used by TCI to encode constant values. */
     TCG_CONST = UINT8_MAX
 } TCGReg;
 
-#define TCG_AREG0                       (TCG_TARGET_NB_REGS - 2)
-
 /* Used for function call generation. */
-#define TCG_REG_CALL_STACK              (TCG_TARGET_NB_REGS - 1)
 #define TCG_TARGET_CALL_STACK_OFFSET    0
 #define TCG_TARGET_STACK_ALIGN          16