[RFC,v3,15/24] riscv: tcg-target: Add the add2 and sub2 instructions

Commit Message

Alistair Francis Dec. 8, 2018, 12:48 a.m. UTC

Signed-off-by: Alistair Francis <[e-mail]>
---
 tcg/riscv/tcg-target.inc.c | 55 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

Comments

Richard Henderson Dec. 10, 2018, 5:28 p.m. UTC | #1

On 12/7/18 6:48 PM, Alistair Francis wrote:
> Signed-off-by: Alistair Francis <[e-mail]>
> ---
>  tcg/riscv/tcg-target.inc.c | 55 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)

Reviewed-by: Richard Henderson <[e-mail]>


r~

Richard Henderson Dec. 12, 2018, 2:51 a.m. UTC | #2

On 12/7/18 6:48 PM, Alistair Francis wrote:
> +static void tcg_out_addsub2(TCGContext *s,
> +                            TCGReg rl, TCGReg rh,
> +                            TCGReg al, TCGReg ah,
> +                            TCGReg bl, TCGReg bh,
> +                            bool cbl, bool cbh, bool is_sub, bool is32bit)

bl and bh must be TCGArg, since they may be constants, as indicated by cbl+cbh.


r~

Patch

diff --git a/tcg/riscv/tcg-target.inc.c b/tcg/riscv/tcg-target.inc.c
index 04e81f811a..10bd007cd4 100644
--- a/tcg/riscv/tcg-target.inc.c
+++ b/tcg/riscv/tcg-target.inc.c
@@ -681,3 +681,58 @@  static bool tcg_out_sti(TCGContext *s, TCGType type, TCGArg val,
     }
     return false;
 }
+
+static void tcg_out_addsub2(TCGContext *s,
+                            TCGReg rl, TCGReg rh,
+                            TCGReg al, TCGReg ah,
+                            TCGReg bl, TCGReg bh,
+                            bool cbl, bool cbh, bool is_sub, bool is32bit)
+{
+    const RISCVInsn opc_add = is32bit ? OPC_ADDW : OPC_ADD;
+    const RISCVInsn opc_addi = is32bit ? OPC_ADDIW : OPC_ADDI;
+    const RISCVInsn opc_sub = is32bit ? OPC_SUBW : OPC_SUB;
+    TCGReg th = TCG_REG_TMP1;
+
+    /* If we have a negative constant such that negating it would
+       make the high part zero, we can (usually) eliminate one insn.  */
+    if (cbl && cbh && bh == -1 && bl != 0) {
+        bl = -bl;
+        bh = 0;
+        is_sub = !is_sub;
+    }
+
+    /* By operating on the high part first, we get to use the final
+       carry operation to move back from the temporary.  */
+    if (!cbh) {
+        tcg_out_opc_reg(s, (is_sub ? opc_sub : opc_add), th, ah, bh);
+    } else if (bh != 0 || ah == rl) {
+        tcg_out_opc_imm(s, opc_addi, th, ah, (is_sub ? -bh : bh));
+    } else {
+        th = ah;
+    }
+
+    /* Note that tcg optimization should eliminate the bl == 0 case.  */
+    if (is_sub) {
+        if (cbl) {
+            tcg_out_opc_imm(s, OPC_SLTIU, TCG_REG_TMP0, al, bl);
+            tcg_out_opc_imm(s, opc_addi, rl, al, -bl);
+        } else {
+            tcg_out_opc_reg(s, OPC_SLTU, TCG_REG_TMP0, al, bl);
+            tcg_out_opc_reg(s, opc_sub, rl, al, bl);
+        }
+        tcg_out_opc_reg(s, opc_sub, rh, th, TCG_REG_TMP0);
+    } else {
+        if (cbl) {
+            tcg_out_opc_imm(s, opc_addi, rl, al, bl);
+            tcg_out_opc_imm(s, OPC_SLTIU, TCG_REG_TMP0, rl, bl);
+        } else if (rl == al && rl == bl) {
+            tcg_out_opc_imm(s, OPC_SLTI, TCG_REG_TMP0, al, 0);
+            tcg_out_opc_reg(s, opc_addi, rl, al, bl);
+        } else {
+            tcg_out_opc_reg(s, opc_add, rl, al, bl);
+            tcg_out_opc_reg(s, OPC_SLTU, TCG_REG_TMP0,
+                            rl, (rl == bl ? al : bl));
+        }
+        tcg_out_opc_reg(s, opc_add, rh, th, TCG_REG_TMP0);
+    }
+}