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[RFC,v2,08/24] riscv: tcg-target: Add the immediate encoders

Message ID 0ee380a9ce2d7290523b5d06597c74ea14ff4174.1543352682.git.alistair.francis@wdc.com
State New
Headers show
Series Add RISC-V TCG backend support | expand

Commit Message

Alistair Francis Nov. 27, 2018, 9:07 p.m. UTC 
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>
---
 tcg/riscv/tcg-target.inc.c | 105 +++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)

Comments

Richard Henderson Nov. 28, 2018, 7:36 p.m. UTC | #1 
On 11/27/18 1:07 PM, Alistair Francis wrote:
> +void tb_target_set_jmp_target(uintptr_t tc_ptr, uintptr_t jmp_addr,
> +                              uintptr_t addr)
> +{
> +    intptr_t offset = (intptr_t)addr - (intptr_t)jmp_addr;
> +    tcg_debug_assert(offset == (int32_t)offset);
> +
> +    int32_t hi20 = ((offset + 0x800) >> 12) << 12;
> +    int32_t lo12 = offset - hi20;
> +
> +    atomic_set((uint32_t *)jmp_addr, encode_uimm20(hi20));
> +    atomic_set((uint32_t *)jmp_addr + 4, encode_imm12(lo12));
> +
> +    flush_icache_range(jmp_addr, jmp_addr + 8);
> +}

Two atomic_sets do not help.  You want a single 64-bit atomic_set updating both
insns simultaneously.  But since you're currently setting

> +#define TCG_TARGET_HAS_direct_jump      0

this code isn't used at all.  Better to simply remove it for now.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~
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Patch

diff --git a/tcg/riscv/tcg-target.inc.c b/tcg/riscv/tcg-target.inc.c
index 5719af3c08..c659c4de39 100644
--- a/tcg/riscv/tcg-target.inc.c
+++ b/tcg/riscv/tcg-target.inc.c
@@ -252,3 +252,108 @@  typedef enum {
     OPC_FENCE_R_RW = 0x0230000f,
     OPC_FENCE_RW_W = 0x0310000f,
 } RISCVInsn;
+
+/*
+ * RISC-V immediate and instruction encoders (excludes 16-bit RVC)
+ */
+
+/* Type-R */
+
+static int32_t encode_r(RISCVInsn opc, TCGReg rd, TCGReg rs1, TCGReg rs2)
+{
+    return opc | (rd & 0x1f) << 7 | (rs1 & 0x1f) << 15 | (rs2 & 0x1f) << 20;
+}
+
+/* Type-I */
+
+static int32_t encode_imm12(uint32_t imm)
+{
+    return (imm & 0xfff) << 20;
+}
+
+static int32_t encode_i(RISCVInsn opc, TCGReg rd, TCGReg rs1, uint32_t imm)
+{
+    return opc | (rd & 0x1f) << 7 | (rs1 & 0x1f) << 15 | encode_imm12(imm);
+}
+
+/* Type-S */
+
+static int32_t encode_simm12(uint32_t imm)
+{
+    int32_t ret = 0;
+
+    ret |= (imm & 0xFE0) << 20;
+    ret |= (imm & 0x1F) << 7;
+
+    return ret;
+}
+
+static int32_t encode_s(RISCVInsn opc, TCGReg rs1, TCGReg rs2, uint32_t imm)
+{
+    return opc | (rs1 & 0x1f) << 15 | (rs2 & 0x1f) << 20 | encode_simm12(imm);
+}
+
+/* Type-SB */
+
+static int32_t encode_sbimm12(uint32_t imm)
+{
+    int32_t ret = 0;
+
+    ret |= (imm & 0x1000) << 19;
+    ret |= (imm & 0x7e0) << 20;
+    ret |= (imm & 0x1e) << 7;
+    ret |= (imm & 0x800) >> 4;
+
+    return ret;
+}
+
+static int32_t encode_sb(RISCVInsn opc, TCGReg rs1, TCGReg rs2, uint32_t imm)
+{
+    return opc | (rs1 & 0x1f) << 15 | (rs2 & 0x1f) << 20 | encode_sbimm12(imm);
+}
+
+/* Type-U */
+
+static int32_t encode_uimm20(uint32_t imm)
+{
+    return imm & 0xfffff000;
+}
+
+static int32_t encode_u(RISCVInsn opc, TCGReg rd, uint32_t imm)
+{
+    return opc | (rd & 0x1f) << 7 | encode_uimm20(imm);
+}
+
+/* Type-UJ */
+
+static int32_t encode_ujimm12(uint32_t imm)
+{
+    int32_t ret = 0;
+
+    ret |= (imm & 0x100000) << 11;
+    ret |= (imm & 0xffe) << 20;
+    ret |= (imm & 0x800) << 9;
+    ret |= imm & 0xff000;
+
+    return ret;
+}
+
+static int32_t encode_uj(RISCVInsn opc, TCGReg rd, uint32_t imm)
+{
+    return opc | (rd & 0x1f) << 7 | encode_ujimm12(imm);
+}
+
+void tb_target_set_jmp_target(uintptr_t tc_ptr, uintptr_t jmp_addr,
+                              uintptr_t addr)
+{
+    intptr_t offset = (intptr_t)addr - (intptr_t)jmp_addr;
+    tcg_debug_assert(offset == (int32_t)offset);
+
+    int32_t hi20 = ((offset + 0x800) >> 12) << 12;
+    int32_t lo12 = offset - hi20;
+
+    atomic_set((uint32_t *)jmp_addr, encode_uimm20(hi20));
+    atomic_set((uint32_t *)jmp_addr + 4, encode_imm12(lo12));
+
+    flush_icache_range(jmp_addr, jmp_addr + 8);
+}