tcg: Introduce tcg_target_call_oarg_reg

Replace the flat array tcg_target_call_oarg_regs[] with
a function call including the TCGCallReturnKind.

Extend the set of registers for ARM to r0-r3 to match the ABI:
https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst#result-return

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/aarch64/tcg-target.c.inc

@@ -63,9 +63,13 @@ static const int tcg_target_call_iarg_regs[8] = {
     TCG_REG_X0, TCG_REG_X1, TCG_REG_X2, TCG_REG_X3,
     TCG_REG_X4, TCG_REG_X5, TCG_REG_X6, TCG_REG_X7
 };
-static const int tcg_target_call_oarg_regs[1] = {
-    TCG_REG_X0
-};
+
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 1);
+    return TCG_REG_X0 + slot;
+}
 
 #define TCG_REG_TMP TCG_REG_X30
 #define TCG_VEC_TMP TCG_REG_V31

tcg/arm/tcg-target.c.inc

@@ -79,9 +79,13 @@ static const int tcg_target_reg_alloc_order[] = {
 static const int tcg_target_call_iarg_regs[4] = {
     TCG_REG_R0, TCG_REG_R1, TCG_REG_R2, TCG_REG_R3
 };
-static const int tcg_target_call_oarg_regs[2] = {
-    TCG_REG_R0, TCG_REG_R1
-};
+
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 3);
+    return TCG_REG_R0 + slot;
+}
 
 #define TCG_REG_TMP  TCG_REG_R12
 #define TCG_VEC_TMP  TCG_REG_Q15

tcg/i386/tcg-target.c.inc

@@ -109,12 +109,16 @@ static const int tcg_target_call_iarg_regs[] = {
 #endif
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_EAX,
-#if TCG_TARGET_REG_BITS == 32
-    TCG_REG_EDX
-#endif
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    switch (kind) {
+    case TCG_CALL_RET_NORMAL:
+        tcg_debug_assert(slot >= 0 && slot <= 1);
+        return slot ? TCG_REG_EDX : TCG_REG_EAX;
+    default:
+        g_assert_not_reached();
+    }
+}
 
 /* Constants we accept.  */
 #define TCG_CT_CONST_S32 0x100

tcg/loongarch64/tcg-target.c.inc

@@ -114,10 +114,12 @@ static const int tcg_target_call_iarg_regs[] = {
     TCG_REG_A7,
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_A0,
-    TCG_REG_A1,
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 1);
+    return TCG_REG_A0 + slot;
+}
 
 #ifndef CONFIG_SOFTMMU
 #define USE_GUEST_BASE     (guest_base != 0)

tcg/mips/tcg-target.c.inc

@@ -136,10 +136,12 @@ static const TCGReg tcg_target_call_iarg_regs[] = {
 #endif
 };
 
-static const TCGReg tcg_target_call_oarg_regs[2] = {
-    TCG_REG_V0,
-    TCG_REG_V1
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 1);
+    return TCG_REG_V0 + slot;
+}
 
 static const tcg_insn_unit *tb_ret_addr;
 static const tcg_insn_unit *bswap32_addr;

tcg/ppc/tcg-target.c.inc

@@ -186,10 +186,12 @@ static const int tcg_target_call_iarg_regs[] = {
     TCG_REG_R10
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_R3,
-    TCG_REG_R4
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 1);
+    return TCG_REG_R3 + slot;
+}
 
 static const int tcg_target_callee_save_regs[] = {
 #ifdef _CALL_DARWIN

tcg/riscv/tcg-target.c.inc

@@ -113,10 +113,12 @@ static const int tcg_target_call_iarg_regs[] = {
     TCG_REG_A7,
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_A0,
-    TCG_REG_A1,
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 1);
+    return TCG_REG_A0 + slot;
+}
 
 #define TCG_CT_CONST_ZERO  0x100
 #define TCG_CT_CONST_S12   0x200

tcg/s390x/tcg-target.c.inc

@@ -402,9 +402,12 @@ static const int tcg_target_call_iarg_regs[] = {
     TCG_REG_R6,
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_R2,
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot == 0);
+    return TCG_REG_R2;
+}
 
 #define S390_CC_EQ      8
 #define S390_CC_LT      4

tcg/sparc64/tcg-target.c.inc

@@ -132,12 +132,12 @@ static const int tcg_target_call_iarg_regs[6] = {
     TCG_REG_O5,
 };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_O0,
-    TCG_REG_O1,
-    TCG_REG_O2,
-    TCG_REG_O3,
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot <= 3);
+    return TCG_REG_O0 + slot;
+}
 
 #define INSN_OP(x)  ((x) << 30)
 #define INSN_OP2(x) ((x) << 22)

tcg/tcg.c

@@ -151,6 +151,7 @@ static bool tcg_out_sti(TCGContext *s, TCGType type, TCGArg val,
                         TCGReg base, intptr_t ofs);
 static void tcg_out_call(TCGContext *s, const tcg_insn_unit *target,
                          const TCGHelperInfo *info);
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot);
 static bool tcg_target_const_match(int64_t val, TCGType type, int ct);
 #ifdef TCG_TARGET_NEED_LDST_LABELS
 static int tcg_out_ldst_finalize(TCGContext *s);
@@ -740,14 +741,16 @@ static void init_call_layout(TCGHelperInfo *info)
     case dh_typecode_s64:
         info->nr_out = 64 / TCG_TARGET_REG_BITS;
         info->out_kind = TCG_CALL_RET_NORMAL;
-        assert(info->nr_out <= ARRAY_SIZE(tcg_target_call_oarg_regs));
+        /* Query the last register now to trigger any assert early. */
+        tcg_target_call_oarg_reg(info->out_kind, info->nr_out - 1);
         break;
     case dh_typecode_i128:
         info->nr_out = 128 / TCG_TARGET_REG_BITS;
         info->out_kind = TCG_CALL_RET_NORMAL; /* TODO */
         switch (/* TODO */ TCG_CALL_RET_NORMAL) {
         case TCG_CALL_RET_NORMAL:
-            assert(info->nr_out <= ARRAY_SIZE(tcg_target_call_oarg_regs));
+            /* Query the last register now to trigger any assert early. */
+            tcg_target_call_oarg_reg(info->out_kind, info->nr_out - 1);
             break;
         case TCG_CALL_RET_BY_REF:
             /*
@@ -4592,7 +4595,7 @@ static void tcg_reg_alloc_call(TCGContext *s, TCGOp *op)
     case TCG_CALL_RET_NORMAL:
         for (i = 0; i < nb_oargs; i++) {
             TCGTemp *ts = arg_temp(op->args[i]);
-            TCGReg reg = tcg_target_call_oarg_regs[i];
+            TCGReg reg = tcg_target_call_oarg_reg(TCG_CALL_RET_NORMAL, i);
 
             /* ENV should not be modified.  */
             tcg_debug_assert(!temp_readonly(ts));

tcg/tci/tcg-target.c.inc

@@ -200,12 +200,12 @@ static const int tcg_target_reg_alloc_order[] = {
 /* No call arguments via registers.  All will be stored on the "stack". */
 static const int tcg_target_call_iarg_regs[] = { };
 
-static const int tcg_target_call_oarg_regs[] = {
-    TCG_REG_R0,
-#if TCG_TARGET_REG_BITS == 32
-    TCG_REG_R1
-#endif
-};
+static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
+{
+    tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
+    tcg_debug_assert(slot >= 0 && slot < 64 / TCG_TARGET_REG_BITS);
+    return TCG_REG_R0 + slot;
+}
 
 #ifdef CONFIG_DEBUG_TCG
 static const char *const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {