Xiao ESP32-C3（基于 RISC-V）浮点汇编指令上无法识别的操作码

问题描述 投票：0回答：1

我正在尝试在 Seeed Xiao ESP32-C3 上实现 Ivan Kostoski 的代码，用于基于 ESP32 的声级计。

根据 Seeed 的 wiki，该芯片“是一款 32 位 RISC-V CPU，其中包括用于 32 位单精度算术的 FPU（浮点单元）”。因此，基于此我编写了一些用于浮点运算的 RISC-V 汇编代码。但是，当我尝试编译时，每个浮点指令都会出现错误

unrecognized opcode
。其他指令不会引发错误。

这是 Arduino IDE 控制台输出。请注意第一条指令 (

addi
) 不会引发错误。

C:\...\cc4DgX57.s: Assembler messages:
C:\...\cc4DgX57.s:12: Error: unrecognized opcode `flw f0,0(a5)'
C:\...\cc4DgX57.s:13: Error: unrecognized opcode `flw f1,4(a5)'
C:\...\cc4DgX57.s:14: Error: unrecognized opcode `flw f2,8(a5)'
C:\...\cc4DgX57.s:15: Error: unrecognized opcode `flw f3,12(a5)'
C:\...\cc4DgX57.s:16: Error: unrecognized opcode `flw f4,0(a6)'
C:\...\cc4DgX57.s:17: Error: unrecognized opcode `flw f5,4(a6)'
C:\...\cc4DgX57.s:22: Error: unrecognized opcode `flw f6,a2'
C:\...\cc4DgX57.s:24: Error: unrecognized opcode `fmadd.s f6,f2,f4'
C:\...\cc4DgX57.s:25: Error: unrecognized opcode `fmadd.s f6,f3,f5'
C:\...\cc4DgX57.s:26: Error: unrecognized opcode `fmv.s f7,f6'
C:\...\cc4DgX57.s:27: Error: unrecognized opcode `fmadd.s f7,f0,f4'
C:\...\cc4DgX57.s:28: Error: unrecognized opcode `fmadd.s f7,f1,f5'
C:\...\cc4DgX57.s:29: Error: unrecognized opcode `fsw f7,a3'
C:\...\cc4DgX57.s:31: Error: unrecognized opcode `fmv.s f5,f4'
C:\...\cc4DgX57.s:32: Error: unrecognized opcode `fmv.s f4,f6'
C:\...\cc4DgX57.s:34: Error: backward ref to unknown label "1:"
C:\...\cc4DgX57.s:37: Error: unrecognized opcode `fsw f4,0(a6)'
C:\...\cc4DgX57.s:38: Error: unrecognized opcode `fsw f5,4(a6)'
C:\...\cc4DgX57.s:39: Error: unrecognized opcode `fmvi a2,0'
C:\...\cc4DgX57.s:48: Error: unrecognized opcode `flw f0,0(a5)'
C:\...\cc4DgX57.s:49: Error: unrecognized opcode `flw f1,4(a5)'
C:\...\cc4DgX57.s:50: Error: unrecognized opcode `flw f2,8(a5)'
C:\...\cc4DgX57.s:51: Error: unrecognized opcode `flw f3,12(a5)'
C:\...\cc4DgX57.s:52: Error: unrecognized opcode `flw f4,0(a6)'
C:\...\cc4DgX57.s:53: Error: unrecognized opcode `flw f5,4(a6)'
C:\...\cc4DgX57.s:54: Error: unrecognized opcode `fmv.s f6,a7'
C:\...\cc4DgX57.s:55: Error: unrecognized opcode `fli f10,0.0'
C:\...\cc4DgX57.s:56: Error: symbol `loop' is already defined
C:\...\cc4DgX57.s:59: Error: symbol `i' is already defined
C:\...\cc4DgX57.s:60: Error: unrecognized opcode `flw f7,a2'
C:\...\cc4DgX57.s:62: Error: unrecognized opcode `fmadd.s f7,f2,f4'
C:\...\cc4DgX57.s:63: Error: unrecognized opcode `fmadd.s f7,f3,f5'
C:\...\cc4DgX57.s:64: Error: unrecognized opcode `fmv.s f8,f7'
C:\...\cc4DgX57.s:65: Error: unrecognized opcode `fmadd.s f8,f0,f4'
C:\...\cc4DgX57.s:66: Error: unrecognized opcode `fmadd.s f8,f1,f5'
C:\...\cc4DgX57.s:67: Error: unrecognized opcode `fmul.s f9,f8,f6'
C:\...\cc4DgX57.s:68: Error: unrecognized opcode `fsw f9,a3'
C:\...\cc4DgX57.s:70: Error: unrecognized opcode `fmv.s f5,f4'
C:\...\cc4DgX57.s:71: Error: unrecognized opcode `fmv.s f4,f7'
C:\...\cc4DgX57.s:72: Error: unrecognized opcode `fmadd.s f10,f9,f9'
C:\...\cc4DgX57.s:74: Error: backward ref to unknown label "1:"
C:\...\cc4DgX57.s:76: Error: symbol `exit' is already defined
C:\...\cc4DgX57.s:77: Error: unrecognized opcode `fsw f4,a6,0'
C:\...\cc4DgX57.s:78: Error: unrecognized opcode `fsw f5,a6,4'
C:\...\cc4DgX57.s:79: Error: unrecognized opcode `fmr a2,f10'
C:\...\cc4DgX57.s: Error: local label `"1" (instance number 1 of a fb label)' is not defined

这是用 Xtensa ISA 编写的参考代码，我正在尝试将其移植到 RISC-V：

extern "C" {
  int sos_filter_f32(float *input, float *output, int len, const SOS_Coefficients &coeffs, SOS_Delay_State &w);
} 
__asm__ (
  //
  // ESP32 implementation of IIR Second-Order Section filter 
  // Assumes a0 and b0 coefficients are one (1.0)
  //
  // float* a2 = input;
  // float* a3 = output;
  // int    a4 = len;
  // float* a5 = coeffs;
  // float* a6 = w; 
  // float  a7 = gain;
  //
  ".text                    \n"
  ".align  4                \n"
  ".global sos_filter_f32   \n"
  ".type   sos_filter_f32,@function\n"
  "sos_filter_f32:          \n"
  "  entry   a1, 16         \n"
  "  lsi     f0, a5, 0      \n" // float f0 = coeffs.b1;
  "  lsi     f1, a5, 4      \n" // float f1 = coeffs.b2;
  "  lsi     f2, a5, 8      \n" // float f2 = coeffs.a1;
  "  lsi     f3, a5, 12     \n" // float f3 = coeffs.a2;
  "  lsi     f4, a6, 0      \n" // float f4 = w[0];
  "  lsi     f5, a6, 4      \n" // float f5 = w[1];
  "  loopnez a4, 1f         \n" // for (; len>0; len--) { 
  "    lsip    f6, a2, 4    \n" //   float f6 = *input++;
  "    madd.s  f6, f2, f4   \n" //   f6 += f2 * f4; // coeffs.a1 * w0
  "    madd.s  f6, f3, f5   \n" //   f6 += f3 * f5; // coeffs.a2 * w1
  "    mov.s   f7, f6       \n" //   f7 = f6; // b0 assumed 1.0
  "    madd.s  f7, f0, f4   \n" //   f7 += f0 * f4; // coeffs.b1 * w0
  "    madd.s  f7, f1, f5   \n" //   f7 += f1 * f5; // coeffs.b2 * w1 -> result
  "    ssip    f7, a3, 4    \n" //   *output++ = f7;
  "    mov.s   f5, f4       \n" //   f5 = f4; // w1 = w0
  "    mov.s   f4, f6       \n" //   f4 = f6; // w0 = f6
  "  1:                     \n" // }
  "  ssi     f4, a6, 0      \n" // w[0] = f4;
  "  ssi     f5, a6, 4      \n" // w[1] = f5;
  "  movi.n   a2, 0         \n" // return 0;
  "  retw.n                 \n"
);

extern "C" {
  float sos_filter_sum_sqr_f32(float *input, float *output, int len, const SOS_Coefficients &coeffs, SOS_Delay_State &w, float gain);
}
__asm__ (
  //
  // ESP32 implementation of IIR Second-Order section filter with applied gain.
  // Assumes a0 and b0 coefficients are one (1.0)
  // Returns sum of squares of filtered samples
  //
  // float* a2 = input;
  // float* a3 = output;
  // int    a4 = len;
  // float* a5 = coeffs;
  // float* a6 = w;
  // float  a7 = gain;
  //
  ".text                    \n"
  ".align  4                \n"
  ".global sos_filter_sum_sqr_f32 \n"
  ".type   sos_filter_sum_sqr_f32,@function \n"
  "sos_filter_sum_sqr_f32:  \n"
  "  entry   a1, 16         \n" 
  "  lsi     f0, a5, 0      \n"  // float f0 = coeffs.b1;
  "  lsi     f1, a5, 4      \n"  // float f1 = coeffs.b2;
  "  lsi     f2, a5, 8      \n"  // float f2 = coeffs.a1;
  "  lsi     f3, a5, 12     \n"  // float f3 = coeffs.a2;
  "  lsi     f4, a6, 0      \n"  // float f4 = w[0];
  "  lsi     f5, a6, 4      \n"  // float f5 = w[1];
  "  wfr     f6, a7         \n"  // float f6 = gain;
  "  const.s f10, 0         \n"  // float sum_sqr = 0;
  "  loopnez a4, 1f         \n"  // for (; len>0; len--) {
  "    lsip    f7, a2, 4    \n"  //   float f7 = *input++;
  "    madd.s  f7, f2, f4   \n"  //   f7 += f2 * f4; // coeffs.a1 * w0
  "    madd.s  f7, f3, f5   \n"  //   f7 += f3 * f5; // coeffs.a2 * w1;
  "    mov.s   f8, f7       \n"  //   f8 = f7; // b0 assumed 1.0
  "    madd.s  f8, f0, f4   \n"  //   f8 += f0 * f4; // coeffs.b1 * w0;
  "    madd.s  f8, f1, f5   \n"  //   f8 += f1 * f5; // coeffs.b2 * w1; 
  "    mul.s   f9, f8, f6   \n"  //   f9 = f8 * f6;  // f8 * gain -> result
  "    ssip    f9, a3, 4    \n"  //   *output++ = f9;
  "    mov.s   f5, f4       \n"  //   f5 = f4; // w1 = w0
  "    mov.s   f4, f7       \n"  //   f4 = f7; // w0 = f7;
  "    madd.s  f10, f9, f9  \n"  //   f10 += f9 * f9; // sum_sqr += f9 * f9;
  "  1:                     \n"  // }
  "  ssi     f4, a6, 0      \n"  // w[0] = f4;
  "  ssi     f5, a6, 4      \n"  // w[1] = f5;
  "  rfr     a2, f10        \n"  // return sum_sqr; 
  "  retw.n                 \n"  // 
);

这是我的 RISC-V 代码：

extern "C" {
  int sos_filter_f32(float *input, float *output, int len, const SOS_Coefficients &coeffs, SOS_Delay_State &w);
} 
__asm__ (
  //
  // RISC-V implementation of IIR Second-Order Section filter 
  // Assumes a0 and b0 coefficients are one (1.0)
  //
  // float* a2 = input;
  // float* a3 = output;
  // int    a4 = len;
  // float* a5 = coeffs;
  // float* a6 = w; 
  // float  a7 = gain;
  //
  ".text                    \n"
  ".p2align  2              \n"
  ".globl sos_filter_f32    \n"
  ".type   sos_filter_f32,@function\n"
  "sos_filter_f32:          \n"
  "  addi sp, sp, -16       \n"
  "  flw     f0, 0(a5)      \n" // float f0 = coeffs.b1;
  "  flw     f1, 4(a5)      \n" // float f1 = coeffs.b2;
  "  flw     f2, 8(a5)      \n" // float f2 = coeffs.a1;
  "  flw     f3, 12(a5)     \n" // float f3 = coeffs.a2;
  "  flw     f4, 0(a6)      \n" // float f4 = w[0];
  "  flw     f5, 4(a6)      \n" // float f5 = w[1];
  "  loop:                  \n"
  "    bnez    a4, 1f       \n" // for (; len>0; len--) { 
  "    j exit               \n"
  "  i:                     \n"
  "    flw     f6, a2       \n" //   float f6 = *input++;
  "    addi    a2, a2, 4    \n" //   post-increment by 4
  "    fmadd.s f6, f2, f4   \n" //   f6 += f2 * f4; // coeffs.a1 * w0
  "    fmadd.s f6, f3, f5   \n" //   f6 += f3 * f5; // coeffs.a2 * w1
  "    fmv.s   f7, f6       \n" //   f7 = f6; // b0 assumed 1.0
  "    fmadd.s f7, f0, f4   \n" //   f7 += f0 * f4; // coeffs.b1 * w0
  "    fmadd.s f7, f1, f5   \n" //   f7 += f1 * f5; // coeffs.b2 * w1 -> result
  "    fsw     f7, a3       \n" //   *output++ = f7;
  "    addi    a3, a3, 4    \n" //   post-increment by 4
  "    fmv.s   f5, f4       \n" //   f5 = f4; // w1 = w0
  "    fmv.s   f4, f6       \n" //   f4 = f6; // w0 = f6
  "    addi    a4, a4, -1   \n" //   update loop counter
  "    bnez    a4, 1b       \n"
  "    j exit               \n"
  "  exit:                  \n" // }
  "  fsw     f4, 0(a6)      \n" // w[0] = f4;
  "  fsw     f5, 4(a6)      \n" // w[1] = f5;
  "  fmvi    a2, 0          \n" // return 0;
  "  ret                    \n"
);

extern "C" {
  float sos_filter_sum_sqr_f32(float *input, float *output, int len, const SOS_Coefficients &coeffs, SOS_Delay_State &w, float gain);
}
__asm__ (
  //
  // RISC-V implementation of IIR Second-Order section filter with applied gain.
  // Assumes a0 and b0 coefficients are one (1.0)
  // Returns sum of squares of filtered samples
  //
  // float* a2 = input;
  // float* a3 = output;
  // int    a4 = len;
  // float* a5 = coeffs;
  // float* a6 = w;
  // float  a7 = gain;
  //
  ".text                    \n"
  ".p2align  2              \n"
  ".globl sos_filter_sum_sqr_f32 \n"
  ".type   sos_filter_sum_sqr_f32,@function \n"
  "sos_filter_sum_sqr_f32:  \n"
  "  addi sp, sp, -16       \n"
  "  flw     f0, 0(a5)      \n" // float f0 = coeffs.b1;
  "  flw     f1, 4(a5)      \n" // float f1 = coeffs.b2;
  "  flw     f2, 8(a5)      \n" // float f2 = coeffs.a1;
  "  flw     f3, 12(a5)     \n" // float f3 = coeffs.a2;
  "  flw     f4, 0(a6)      \n" // float f4 = w[0];
  "  flw     f5, 4(a6)      \n" // float f5 = w[1];
  "  fmv.s   f6, a7         \n" // float f6 = gain;
  "  fli     f10, 0.0       \n" // float sum_sqr = 0;
  "  loop:                  \n"
  "    bnez    a4, 1f       \n" // for (; len>0; len--) {
  "    j exit               \n"
  "  i:                     \n"
  "    flw     f7, a2       \n" //   float f7 = *input++;
  "    addi    a2, a2, 4    \n" //   post-increment by 4
  "    fmadd.s f7, f2, f4   \n" //   f7 += f2 * f4; // coeffs.a1 * w0
  "    fmadd.s f7, f3, f5   \n" //   f7 += f3 * f5; // coeffs.a2 * w1;
  "    fmv.s   f8, f7       \n" //   f8 = f7; // b0 assumed 1.0
  "    fmadd.s f8, f0, f4   \n" //   f8 += f0 * f4; // coeffs.b1 * w0;
  "    fmadd.s f8, f1, f5   \n" //   f8 += f1 * f5; // coeffs.b2 * w1; 
  "    fmul.s  f9, f8, f6   \n" //   f9 = f8 * f6;  // f8 * gain -> result
  "    fsw     f9, a3       \n" //   *output++ = f9;
  "    addi    a3, a3, 4    \n" //   post-increment by 4
  "    fmv.s   f5, f4       \n" //   f5 = f4; // w1 = w0
  "    fmv.s   f4, f7       \n" //   f4 = f7; // w0 = f7;
  "    fmadd.s f10, f9, f9  \n" //   f10 += f9 * f9; // sum_sqr += f9 * f9;
  "    addi    a4, a4, -1   \n" //   update loop counter
  "    bnez    a4, 1b       \n"
  "    j exit               \n"
  "  exit:                  \n" // }
  "  fsw     f4, a6, 0      \n" // w[0] = f4;
  "  fsw     f5, a6, 4      \n" // w[1] = f5;
  "  fmr     a2, f10        \n" // return sum_sqr; 
  "  ret                    \n" // 
);

我正在使用单精度指令，根据制造商的说法，应该支持该指令。尽管如此，

unrecognized opcode
错误表明情况并非如此。

我已将开发板正确安装在 Arduino IDE 上，并且在编译前已选择它，因此代码并不是为不相关的 RISC-V 芯片编译的，不支持浮点。

我的代码的其余部分不是问题，因为我已将上述函数移植到 C++（遵循 Ivan 对汇编代码的注释），并且它们确实可以编译并工作。

assembly esp32 arduino-ide riscv
1个回答
0
投票

Seeed Studio 不是制造商。他们销售使用 ESP32-C3（以及其他 CPU）的开发板，但他们不制造 ESP32-C3。 Espressif 确实如此，关键是查看Espressif 的 CPU 技术参考 文档，而不是 Seeed Studio 的销售信息。

数据表很少指出不支持什么，因此技术参考从未明确指出“不支持浮点扩展”。 RISC V CPU有很多版本；乐鑫将 C3 中使用的 CPU 描述为支持“基本整数 (I)、乘法/除法 (M) 和压缩 (C) 标准扩展”（1.1 ESP RISC V CPU 概述）。

文档后面显示 表示单精度、双精度和四精度浮点扩展均不可用（

misa
- 机器 ISA - 寄存器中的标志）。

您尝试使用的指令 - 

fmadd.s
、
fmv.s
等 - 都是misa寄存器指示不支持的
浮动计算指令
的一部分，这就是您编写的代码不支持的原因不建造。

将 ESP32-C3 与其他 ESP32 CPU 进行比较，您可以将其视为该系列的“价值处理器”。乐鑫当前的 RISC-V CPU 内存较少，为单核，不支持 PSRAM，并且不具备单、双或四 RISC-V 浮点计算扩展。乐鑫的其他 CPU（最初的 ESP32、ESP32-S2 和 ESP32-S3）在不同方面都具有更强的功能，而且成本也更高。

我对您的替代方案的最佳建议是按照@Peter Cordes 在评论中建议的方式进行操作；检查编译器的汇编代码输出，并根据您在其中找到的内容编写代码。

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