[Qemu-devel] [PATCH 3/8] target-mips: mips16 cleanups

[Nathan Froyd]

Change code handling mips16-specific branches to use ISA-neutral special
opcodes.  Since there are several places where the delay slot
requirements for microMIPS branches differ from mips16 branches, using
opcodes is easier than checking hflags, then checking mips16
vs. microMIPS.

Signed-off-by: Nathan Froyd <address@hidden>
---
 target-mips/translate.c |   24 +++++++++++++++++-------
 1 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/target-mips/translate.c b/target-mips/translate.c
index 8d532d5..2754b2e 100644
--- a/target-mips/translate.c
+++ b/target-mips/translate.c
@@ -68,6 +68,7 @@ enum {
     /* Jump and branches */
     OPC_J        = (0x02 << 26),
     OPC_JAL      = (0x03 << 26),
+    OPC_JALS     = OPC_JAL | 0x5,
     OPC_BEQ      = (0x04 << 26),  /* Unconditional if rs = rt = 0 (B) */
     OPC_BEQL     = (0x14 << 26),
     OPC_BNE      = (0x05 << 26),
@@ -77,6 +78,7 @@ enum {
     OPC_BGTZ     = (0x07 << 26),
     OPC_BGTZL    = (0x17 << 26),
     OPC_JALX     = (0x1D << 26),  /* MIPS 16 only */
+    OPC_JALXS    = OPC_JALX | 0x5,
     /* Load and stores */
     OPC_LDL      = (0x1A << 26),
     OPC_LDR      = (0x1B << 26),
@@ -177,6 +179,7 @@ enum {
     OPC_JR       = 0x08 | OPC_SPECIAL, /* Also JR.HB */
     OPC_JALR     = 0x09 | OPC_SPECIAL, /* Also JALR.HB */
     OPC_JALRC    = OPC_JALR | (0x5 << 6),
+    OPC_JALRS    = 0x10 | OPC_SPECIAL | (0x5 << 6),
     /* Traps */
     OPC_TGE      = 0x30 | OPC_SPECIAL,
     OPC_TGEU     = 0x31 | OPC_SPECIAL,
@@ -2466,12 +2469,15 @@ static void gen_compute_branch (DisasContext *ctx, 
uint32_t opc,
     case OPC_J:
     case OPC_JAL:
     case OPC_JALX:
+    case OPC_JALS:
+    case OPC_JALXS:
         /* Jump to immediate */
         btgt = ((ctx->pc + insn_bytes) & (int32_t)0xF0000000) | 
(uint32_t)offset;
         break;
     case OPC_JR:
     case OPC_JALR:
     case OPC_JALRC:
+    case OPC_JALRS:
         /* Jump to register */
         if (offset != 0 && offset != 16) {
             /* Hint = 0 is JR/JALR, hint 16 is JR.HB/JALR.HB, the
@@ -2534,29 +2540,33 @@ static void gen_compute_branch (DisasContext *ctx, 
uint32_t opc,
             ctx->hflags |= MIPS_HFLAG_B;
             MIPS_DEBUG("j " TARGET_FMT_lx, btgt);
             break;
+        case OPC_JALXS:           
         case OPC_JALX:
             ctx->hflags |= MIPS_HFLAG_BX;
             /* Fallthrough */
+        case OPC_JALS:
         case OPC_JAL:
             blink = 31;
             ctx->hflags |= MIPS_HFLAG_B;
-            ctx->hflags |= (ctx->hflags & MIPS_HFLAG_M16
+            ctx->hflags |= ((opc == OPC_JALS || opc == OPC_JALXS)
                             ? MIPS_HFLAG_BDS16
                             : MIPS_HFLAG_BDS32);
             MIPS_DEBUG("jal " TARGET_FMT_lx, btgt);
             break;
         case OPC_JR:
             ctx->hflags |= MIPS_HFLAG_BR;
-            if (ctx->hflags & MIPS_HFLAG_M16)
-                ctx->hflags |= MIPS_HFLAG_BDS16;
+            if (insn_bytes == 4)
+                ctx->hflags |= MIPS_HFLAG_BDS32;
             MIPS_DEBUG("jr %s", regnames[rs]);
             break;
+        case OPC_JALRS:
         case OPC_JALR:
         case OPC_JALRC:
             blink = rt;
             ctx->hflags |= MIPS_HFLAG_BR;
-            if (ctx->hflags & MIPS_HFLAG_M16)
-                ctx->hflags |= MIPS_HFLAG_BDS16;
+            ctx->hflags |= (opc == OPC_JALRS
+                            ? MIPS_HFLAG_BDS16
+                            : MIPS_HFLAG_BDS32);
             MIPS_DEBUG("jalr %s, %s", regnames[rt], regnames[rs]);
             break;
         default:
@@ -8487,7 +8497,7 @@ static int decode_mips16_opc (CPUState *env, DisasContext 
*ctx,
         offset = (((ctx->opcode & 0x1f) << 21)
                   | ((ctx->opcode >> 5) & 0x1f) << 16
                   | offset) << 2;
-        op = ((ctx->opcode >> 10) & 0x1) ? OPC_JALX : OPC_JAL;
+        op = ((ctx->opcode >> 10) & 0x1) ? OPC_JALXS : OPC_JALS;
         gen_compute_branch(ctx, op, 4, rx, ry, offset);
         n_bytes = 4;
         *is_branch = 1;
@@ -8726,7 +8736,7 @@ static int decode_mips16_opc (CPUState *env, DisasContext 
*ctx,
                 int ra = (ctx->opcode >> 5) & 0x1;
 
                 if (link) {
-                    op = nd ? OPC_JALRC : OPC_JALR;
+                    op = nd ? OPC_JALRC : OPC_JALRS;
                 } else {
                     op = OPC_JR;
                 }
-- 
1.6.3.2