[Qemu-devel] [PULL 08/10] tcg/mips: Support r6 multiply/divide encodings

[Richard Henderson <rth@twiddle.net>]

From: James Hogan <james.hogan@imgtec.com>

MIPSr6 adds several new integer multiply, divide, and modulo
instructions, and removes several pre-r6 encodings, along with the HI/LO
registers which were the implicit operands of some of those
instructions. Update TCG to use the new instructions when built for r6.

The new instructions actually map much more directly to the TCG ops, as
they only provide a single 32-bit half of the result and in a normal
general purpose register instead of HI or LO.

The mulu2_i32 and muls2_i32 operations are no longer appropriate for r6,
so they are removed from the TCG opcode table. This is because they
would need to emit two separate host instructions anyway (for the high
and low half of the result), which TCG can arrange automatically for us
in the absense of mulu2_i32/muls2_i32 by splitting it into mul_i32 and
mul*h_i32 TCG ops.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-Id: <1443788657-14537-6-git-send-email-james.hogan@imgtec.com>
---
 tcg/mips/tcg-target.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 tcg/mips/tcg-target.h |  4 ++--
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
index c08418c..a937b14 100644
--- a/tcg/mips/tcg-target.c
+++ b/tcg/mips/tcg-target.c
@@ -295,9 +295,17 @@ typedef enum {
     OPC_MFHI     = OPC_SPECIAL | 0x10,
     OPC_MFLO     = OPC_SPECIAL | 0x12,
     OPC_MULT     = OPC_SPECIAL | 0x18,
+    OPC_MUL_R6   = OPC_SPECIAL | (0x02 <<  6) | 0x18,
+    OPC_MUH      = OPC_SPECIAL | (0x03 <<  6) | 0x18,
     OPC_MULTU    = OPC_SPECIAL | 0x19,
+    OPC_MULU     = OPC_SPECIAL | (0x02 <<  6) | 0x19,
+    OPC_MUHU     = OPC_SPECIAL | (0x03 <<  6) | 0x19,
     OPC_DIV      = OPC_SPECIAL | 0x1A,
+    OPC_DIV_R6   = OPC_SPECIAL | (0x02 <<  6) | 0x1A,
+    OPC_MOD      = OPC_SPECIAL | (0x03 <<  6) | 0x1A,
     OPC_DIVU     = OPC_SPECIAL | 0x1B,
+    OPC_DIVU_R6  = OPC_SPECIAL | (0x02 <<  6) | 0x1B,
+    OPC_MODU     = OPC_SPECIAL | (0x03 <<  6) | 0x1B,
     OPC_ADDU     = OPC_SPECIAL | 0x21,
     OPC_SUBU     = OPC_SPECIAL | 0x23,
     OPC_AND      = OPC_SPECIAL | 0x24,
@@ -312,7 +320,7 @@ typedef enum {
     OPC_BGEZ     = OPC_REGIMM | (0x01 << 16),
 
     OPC_SPECIAL2 = 0x1c << 26,
-    OPC_MUL      = OPC_SPECIAL2 | 0x002,
+    OPC_MUL_R5   = OPC_SPECIAL2 | 0x002,
 
     OPC_SPECIAL3 = 0x1f << 26,
     OPC_EXT      = OPC_SPECIAL3 | 0x000,
@@ -323,6 +331,12 @@ typedef enum {
 
     /* MIPS r6 doesn't have JR, JALR should be used instead */
     OPC_JR       = use_mips32r6_instructions ? OPC_JALR : OPC_JR_R5,
+
+    /*
+     * MIPS r6 replaces MUL with an alternative encoding which is
+     * backwards-compatible at the assembly level.
+     */
+    OPC_MUL      = use_mips32r6_instructions ? OPC_MUL_R6 : OPC_MUL_R5,
 } MIPSInsn;
 
 /*
@@ -1448,21 +1462,45 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
         i1 = OPC_MULT, i2 = OPC_MFLO;
         goto do_hilo1;
     case INDEX_op_mulsh_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_MUH, a0, a1, a2);
+            break;
+        }
         i1 = OPC_MULT, i2 = OPC_MFHI;
         goto do_hilo1;
     case INDEX_op_muluh_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_MUHU, a0, a1, a2);
+            break;
+        }
         i1 = OPC_MULTU, i2 = OPC_MFHI;
         goto do_hilo1;
     case INDEX_op_div_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_DIV_R6, a0, a1, a2);
+            break;
+        }
         i1 = OPC_DIV, i2 = OPC_MFLO;
         goto do_hilo1;
     case INDEX_op_divu_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_DIVU_R6, a0, a1, a2);
+            break;
+        }
         i1 = OPC_DIVU, i2 = OPC_MFLO;
         goto do_hilo1;
     case INDEX_op_rem_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_MOD, a0, a1, a2);
+            break;
+        }
         i1 = OPC_DIV, i2 = OPC_MFHI;
         goto do_hilo1;
     case INDEX_op_remu_i32:
+        if (use_mips32r6_instructions) {
+            tcg_out_opc_reg(s, OPC_MODU, a0, a1, a2);
+            break;
+        }
         i1 = OPC_DIVU, i2 = OPC_MFHI;
     do_hilo1:
         tcg_out_opc_reg(s, i1, 0, a1, a2);
@@ -1595,8 +1633,10 @@ static const TCGTargetOpDef mips_op_defs[] = {
 
     { INDEX_op_add_i32, { "r", "rZ", "rJ" } },
     { INDEX_op_mul_i32, { "r", "rZ", "rZ" } },
+#if !use_mips32r6_instructions
     { INDEX_op_muls2_i32, { "r", "r", "rZ", "rZ" } },
     { INDEX_op_mulu2_i32, { "r", "r", "rZ", "rZ" } },
+#endif
     { INDEX_op_mulsh_i32, { "r", "rZ", "rZ" } },
     { INDEX_op_muluh_i32, { "r", "rZ", "rZ" } },
     { INDEX_op_div_i32, { "r", "rZ", "rZ" } },
diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
index e579c10..b1cda37 100644
--- a/tcg/mips/tcg-target.h
+++ b/tcg/mips/tcg-target.h
@@ -112,8 +112,8 @@ extern bool use_mips32r2_instructions;
 #define TCG_TARGET_HAS_orc_i32          0
 #define TCG_TARGET_HAS_eqv_i32          0
 #define TCG_TARGET_HAS_nand_i32         0
-#define TCG_TARGET_HAS_mulu2_i32        1
-#define TCG_TARGET_HAS_muls2_i32        1
+#define TCG_TARGET_HAS_mulu2_i32        (!use_mips32r6_instructions)
+#define TCG_TARGET_HAS_muls2_i32        (!use_mips32r6_instructions)
 #define TCG_TARGET_HAS_muluh_i32        1
 #define TCG_TARGET_HAS_mulsh_i32        1
 
-- 
2.4.3