riscv: Separate FPU register size from core register size in gdbstub [v2]

The size of the FPU registers is dictated by the 'f' and 'd' features,
not the core processor register size. Processors with the 'd' feature
have 64-bit FPU registers. Processors without the 'd' feature but with
the 'f' feature have 32-bit FPU registers.

Signed-off-by: Keith Packard <keithp@keithp.com>
[Palmer: This requires manually triggering a rebuild of
riscv32-softmmu/gdbstub-xml.c]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

configure

@@ -7736,13 +7736,13 @@ case "$target_name" in
     TARGET_BASE_ARCH=riscv
     TARGET_ABI_DIR=riscv
     mttcg=yes
-    gdb_xml_files="riscv-32bit-cpu.xml riscv-32bit-fpu.xml riscv-32bit-csr.xml riscv-32bit-virtual.xml"
+    gdb_xml_files="riscv-32bit-cpu.xml riscv-32bit-fpu.xml riscv-64bit-fpu.xml riscv-32bit-csr.xml riscv-32bit-virtual.xml"
   ;;
   riscv64)
     TARGET_BASE_ARCH=riscv
     TARGET_ABI_DIR=riscv
     mttcg=yes
-    gdb_xml_files="riscv-64bit-cpu.xml riscv-64bit-fpu.xml riscv-64bit-csr.xml riscv-64bit-virtual.xml"
+    gdb_xml_files="riscv-64bit-cpu.xml riscv-32bit-fpu.xml riscv-64bit-fpu.xml riscv-64bit-csr.xml riscv-64bit-virtual.xml"
   ;;
   sh4|sh4eb)
     TARGET_ARCH=sh4

target/riscv/gdbstub.c

@@ -303,7 +303,12 @@ int riscv_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
 static int riscv_gdb_get_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
 {
     if (n < 32) {
-        return gdb_get_reg64(mem_buf, env->fpr[n]);
+        if (env->misa & RVD) {
+            return gdb_get_reg64(mem_buf, env->fpr[n]);
+        }
+        if (env->misa & RVF) {
+            return gdb_get_reg32(mem_buf, env->fpr[n]);
+        }
     /* there is hole between ft11 and fflags in fpu.xml */
     } else if (n < 36 && n > 32) {
         target_ulong val = 0;
@@ -403,23 +408,20 @@ void riscv_cpu_register_gdb_regs_for_features(CPUState *cs)
 {
     RISCVCPU *cpu = RISCV_CPU(cs);
     CPURISCVState *env = &cpu->env;
-#if defined(TARGET_RISCV32)
-    if (env->misa & RVF) {
+    if (env->misa & RVD) {
+        gdb_register_coprocessor(cs, riscv_gdb_get_fpu, riscv_gdb_set_fpu,
+                                 36, "riscv-64bit-fpu.xml", 0);
+    } else if (env->misa & RVF) {
         gdb_register_coprocessor(cs, riscv_gdb_get_fpu, riscv_gdb_set_fpu,
                                  36, "riscv-32bit-fpu.xml", 0);
     }
-
+#if defined(TARGET_RISCV32)
     gdb_register_coprocessor(cs, riscv_gdb_get_csr, riscv_gdb_set_csr,
                              240, "riscv-32bit-csr.xml", 0);
 
     gdb_register_coprocessor(cs, riscv_gdb_get_virtual, riscv_gdb_set_virtual,
                              1, "riscv-32bit-virtual.xml", 0);
 #elif defined(TARGET_RISCV64)
-    if (env->misa & RVF) {
-        gdb_register_coprocessor(cs, riscv_gdb_get_fpu, riscv_gdb_set_fpu,
-                                 36, "riscv-64bit-fpu.xml", 0);
-    }
-
     gdb_register_coprocessor(cs, riscv_gdb_get_csr, riscv_gdb_set_csr,
                              240, "riscv-64bit-csr.xml", 0);