[Qemu-devel] [PATCH] target-xtensa: add 64-bit floating point registers

[Max Filippov]

Xtensa ISA got specification for 64-bit floating point registers and
opcodes, see ISA, 4.3.11 "Floating point coprocessor option".

Add 64-bit FP registers.

Although 64-bit floating point is currently not supported by xtensa
translator, these registers need to be reported to gdb with proper size,
otherwise it wouldn't find other registers.

Signed-off-by: Max Filippov <address@hidden>
---
 target-xtensa/cpu.h          | 18 +++++++++++++++++-
 target-xtensa/gdbstub.c      | 25 +++++++++++++++++++++----
 target-xtensa/overlay_tool.h |  2 +-
 target-xtensa/translate.c    |  7 ++++---
 4 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/target-xtensa/cpu.h b/target-xtensa/cpu.h
index dfd0d1c..b592efb 100644
--- a/target-xtensa/cpu.h
+++ b/target-xtensa/cpu.h
@@ -287,6 +287,7 @@ typedef struct XtensaGdbReg {
     int targno;
     int type;
     int group;
+    unsigned size;
 } XtensaGdbReg;
 
 typedef struct XtensaGdbRegmap {
@@ -336,6 +337,18 @@ typedef struct XtensaConfigList {
     struct XtensaConfigList *next;
 } XtensaConfigList;
 
+#ifdef HOST_WORDS_BIGENDIAN
+enum {
+    FP_F32_HIGH,
+    FP_F32_LOW,
+};
+#else
+enum {
+    FP_F32_LOW,
+    FP_F32_HIGH,
+};
+#endif
+
 typedef struct CPUXtensaState {
     const XtensaConfig *config;
     uint32_t regs[16];
@@ -343,7 +356,10 @@ typedef struct CPUXtensaState {
     uint32_t sregs[256];
     uint32_t uregs[256];
     uint32_t phys_regs[MAX_NAREG];
-    float32 fregs[16];
+    union {
+        float32 f32[2];
+        float64 f64;
+    } fregs[16];
     float_status fp_status;
 
     xtensa_tlb_entry itlb[7][MAX_TLB_WAY_SIZE];
diff --git a/target-xtensa/gdbstub.c b/target-xtensa/gdbstub.c
index 9e13b20..bc2e1b5 100644
--- a/target-xtensa/gdbstub.c
+++ b/target-xtensa/gdbstub.c
@@ -26,6 +26,7 @@ int xtensa_cpu_gdb_read_register(CPUState *cs, uint8_t 
*mem_buf, int n)
     XtensaCPU *cpu = XTENSA_CPU(cs);
     CPUXtensaState *env = &cpu->env;
     const XtensaGdbReg *reg = env->config->gdb_regmap.reg + n;
+    unsigned i;
 
     if (n < 0 || n >= env->config->gdb_regmap.num_regs) {
         return 0;
@@ -47,8 +48,16 @@ int xtensa_cpu_gdb_read_register(CPUState *cs, uint8_t 
*mem_buf, int n)
         return gdb_get_reg32(mem_buf, env->uregs[reg->targno & 0xff]);
 
     case 4: /*f*/
-        return gdb_get_reg32(mem_buf, float32_val(env->fregs[reg->targno
-                                                             & 0x0f]));
+        i = reg->targno & 0x0f;
+        switch (reg->size) {
+        case 4:
+            return gdb_get_reg32(mem_buf,
+                                 float32_val(env->fregs[i].f32[FP_F32_LOW]));
+        case 8:
+            return gdb_get_reg64(mem_buf, float64_val(env->fregs[i].f64));
+        default:
+            return 0;
+        }
 
     case 8: /*a*/
         return gdb_get_reg32(mem_buf, env->regs[reg->targno & 0x0f]);
@@ -92,8 +101,16 @@ int xtensa_cpu_gdb_write_register(CPUState *cs, uint8_t 
*mem_buf, int n)
         break;
 
     case 4: /*f*/
-        env->fregs[reg->targno & 0x0f] = make_float32(tmp);
-        break;
+        switch (reg->size) {
+        case 4:
+            env->fregs[reg->targno & 0x0f].f32[FP_F32_LOW] = make_float32(tmp);
+            return 4;
+        case 8:
+            env->fregs[reg->targno & 0x0f].f64 = make_float64(tmp);
+            return 8;
+        default:
+            return 0;
+        }
 
     case 8: /*a*/
         env->regs[reg->targno & 0x0f] = tmp;
diff --git a/target-xtensa/overlay_tool.h b/target-xtensa/overlay_tool.h
index 6105d4c..f7b1510 100644
--- a/target-xtensa/overlay_tool.h
+++ b/target-xtensa/overlay_tool.h
@@ -27,7 +27,7 @@
 
 #define XTREG(idx, ofs, bi, sz, al, no, flags, cp, typ, grp, name, \
         a1, a2, a3, a4, a5, a6) \
-    { .targno = (no), .type = (typ), .group = (grp) },
+    { .targno = (no), .type = (typ), .group = (grp), .size = (sz) },
 
 #ifndef XCHAL_HAVE_DIV32
 #define XCHAL_HAVE_DIV32 0
diff --git a/target-xtensa/translate.c b/target-xtensa/translate.c
index 86e4849..f2118c2 100644
--- a/target-xtensa/translate.c
+++ b/target-xtensa/translate.c
@@ -228,7 +228,7 @@ void xtensa_translate_init(void)
 
     for (i = 0; i < 16; i++) {
         cpu_FR[i] = tcg_global_mem_new_i32(TCG_AREG0,
-                offsetof(CPUXtensaState, fregs[i]),
+                offsetof(CPUXtensaState, fregs[i].f32[FP_F32_LOW]),
                 fregnames[i]);
     }
 
@@ -3206,8 +3206,9 @@ void xtensa_cpu_dump_state(CPUState *cs, FILE *f,
 
         for (i = 0; i < 16; ++i) {
             cpu_fprintf(f, "F%02d=%08x (%+10.8e)%c", i,
-                    float32_val(env->fregs[i]),
-                    *(float *)&env->fregs[i], (i % 2) == 1 ? '\n' : ' ');
+                    float32_val(env->fregs[i].f32[FP_F32_LOW]),
+                    *(float *)(env->fregs[i].f32 + FP_F32_LOW),
+                    (i % 2) == 1 ? '\n' : ' ');
         }
     }
 }
-- 
1.8.1.4