Only prohibit float32-only when FP emulation is enabled

machine/fp_asm.S

@@ -2,10 +2,6 @@
 
 #ifdef __riscv_flen
 
-#if __riscv_flen != 64
-# error single-float only is not supported
-#endif
-
 #define get_f32(which) fmv.x.s a0, which; jr t0
 #define put_f32(which) fmv.s.x which, a0; jr t0
 #if __riscv_xlen == 64
@@ -88,7 +84,9 @@
     put_f32(f29)
     put_f32(f30)
     put_f32(f31)
-  
+
+ #if __riscv_flen > 32
+
   .text
   .globl get_f64_reg
   get_f64_reg:
@@ -162,3 +160,5 @@
     put_f64(f31)
 
 #endif
+
+#endif

machine/fp_emulation.c

@@ -6,6 +6,12 @@
 #include "internals.h"
 #include "config.h"
 
+#ifdef PK_ENABLE_FP_EMULATION
+
+#if defined(__riscv_flen) && __riscv_flen != 64
+# error single-float only is not supported
+#endif
+
 DECLARE_EMULATION_FUNC(emulate_fp)
 {
   asm (".pushsection .rodata\n"
@@ -406,3 +412,5 @@ DECLARE_EMULATION_FUNC(emulate_fmadd)
     return truly_illegal_insn(regs, mcause, mepc, mstatus, insn);
   }
 }
+
+#endif

machine/minit.c

@@ -24,7 +24,7 @@ void* kernel_end;
 static void mstatus_init()
 {
   // Enable FPU
-  if (supports_extension('D') || supports_extension('F'))
+  if (supports_extension('F'))
     write_csr(mstatus, MSTATUS_FS);
 
   // Enable user/supervisor use of perf counters
@@ -64,7 +64,7 @@ static void delegate_traps()
 
 static void fp_init()
 {
-  if (!supports_extension('D') && !supports_extension('F'))
+  if (!supports_extension('F'))
     return;
 
   assert(read_csr(mstatus) & MSTATUS_FS);
@@ -73,6 +73,13 @@ static void fp_init()
   for (int i = 0; i < 32; i++)
     init_fp_reg(i);
   write_csr(fcsr, 0);
+
+# if __riscv_flen == 32
+  uintptr_t d_mask = 1 << ('D' - 'A');
+  clear_csr(misa, d_mask);
+  assert(!(read_csr(misa) & d_mask));
+# endif
+
 #else
   uintptr_t fd_mask = (1 << ('F' - 'A')) | (1 << ('D' - 'A'));
   clear_csr(misa, fd_mask);