[Qemu-devel] [PATCH 09/13] target-openrisc: Add CPU which neglects Carry and Overflow Flag

[Sebastian Macke]

The carry and overflag and the instructions l.addc and l.addic
are never used in the toolchain. Linux and gcc compiled software
don't need them. To speed up the emulation a cpu was added which
neglects the flags for l.addi, l.add, l.sub and
generates an illegal instruction error for l.addic and l.addc

This cpu violate the specification and will not run through the
test cases but increases the emulation speed between 20% and 200%.
The cpu is activated by the option "-cpu or1200-noflags"

Signed-off-by: Sebastian Macke <address@hidden>
---
 target-openrisc/cpu.c       | 15 +++++++++++++--
 target-openrisc/cpu.h       |  1 +
 target-openrisc/translate.c | 21 +++++++++++++++++----
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/target-openrisc/cpu.c b/target-openrisc/cpu.c
index 09ba728..c80a30c 100644
--- a/target-openrisc/cpu.c
+++ b/target-openrisc/cpu.c
@@ -124,6 +124,16 @@ static void or1200_initfn(Object *obj)
     set_feature(cpu, OPENRISC_FEATURE_OF32S);
 }
 
+static void or1200_noflags_initfn(Object *obj)
+{
+    OpenRISCCPU *cpu = OPENRISC_CPU(obj);
+
+    set_feature(cpu, OPENRISC_FEATURE_OB32S);
+    set_feature(cpu, OPENRISC_FEATURE_OF32S);
+    set_feature(cpu, OPENRISC_FEATURE_NOFLAGS);
+}
+
+
 static void openrisc_any_initfn(Object *obj)
 {
     OpenRISCCPU *cpu = OPENRISC_CPU(obj);
@@ -137,8 +147,9 @@ typedef struct OpenRISCCPUInfo {
 } OpenRISCCPUInfo;
 
 static const OpenRISCCPUInfo openrisc_cpus[] = {
-    { .name = "or1200",      .initfn = or1200_initfn },
-    { .name = "any",         .initfn = openrisc_any_initfn },
+    { .name = "or1200",         .initfn = or1200_initfn },
+    { .name = "or1200-noflags", .initfn = or1200_noflags_initfn },
+    { .name = "any",            .initfn = openrisc_any_initfn },
 };
 
 static void openrisc_cpu_class_init(ObjectClass *oc, void *data)
diff --git a/target-openrisc/cpu.h b/target-openrisc/cpu.h
index 94bbb17..2423fad 100644
--- a/target-openrisc/cpu.h
+++ b/target-openrisc/cpu.h
@@ -204,6 +204,7 @@ enum {
     OPENRISC_FEATURE_OF32S = (1 << 7),
     OPENRISC_FEATURE_OF64S = (1 << 8),
     OPENRISC_FEATURE_OV64S = (1 << 9),
+    OPENRISC_FEATURE_NOFLAGS = (1 << 10),
 };
 
 /* Tick Timer Mode Register */
diff --git a/target-openrisc/translate.c b/target-openrisc/translate.c
index b1f73c4..d926995 100644
--- a/target-openrisc/translate.c
+++ b/target-openrisc/translate.c
@@ -50,6 +50,7 @@ typedef struct DisasContext {
     TranslationBlock *tb;
     target_ulong pc;
     uint32_t tb_flags, synced_flags, flags;
+    uint32_t cpufeature;
     uint32_t is_jmp;
     uint32_t j_state; /* specifies the jump type*/
     target_ulong j_target; /* target address for jump */
@@ -265,7 +266,9 @@ static void dec_calc(DisasContext *dc, uint32_t insn)
         switch (op1) {
         case 0x00:    /* l.add */
             LOG_DIS("l.add r%d, r%d, r%d\n", rd, ra, rb);
-            {
+            if (dc->cpufeature & OPENRISC_FEATURE_NOFLAGS) {
+                tcg_gen_add_tl(cpu_R[rd], cpu_R[ra], cpu_R[rb]);
+            } else {
                 int lab = gen_new_label();
                 TCGv_i64 ta = tcg_temp_new_i64();
                 TCGv_i64 tb = tcg_temp_new_i64();
@@ -306,7 +309,9 @@ static void dec_calc(DisasContext *dc, uint32_t insn)
         switch (op1) {
         case 0x00:
             LOG_DIS("l.addc r%d, r%d, r%d\n", rd, ra, rb);
-            {
+            if (dc->cpufeature & OPENRISC_FEATURE_NOFLAGS) {
+                gen_illegal_exception(dc);
+            } else {
                 int lab = gen_new_label();
                 TCGv_i64 ta = tcg_temp_new_i64();
                 TCGv_i64 tb = tcg_temp_new_i64();
@@ -355,7 +360,9 @@ static void dec_calc(DisasContext *dc, uint32_t insn)
         switch (op1) {
         case 0x00:
             LOG_DIS("l.sub r%d, r%d, r%d\n", rd, ra, rb);
-            {
+            if (dc->cpufeature & OPENRISC_FEATURE_NOFLAGS) {
+                tcg_gen_sub_tl(cpu_R[rd], cpu_R[ra], cpu_R[rb]);
+            } else {
                 int lab = gen_new_label();
                 TCGv_i64 ta = tcg_temp_new_i64();
                 TCGv_i64 tb = tcg_temp_new_i64();
@@ -952,7 +959,9 @@ static void dec_misc(DisasContext *dc, uint32_t insn)
 
     case 0x27:    /* l.addi */
         LOG_DIS("l.addi r%d, r%d, %d\n", rd, ra, I16);
-        {
+        if (dc->cpufeature & OPENRISC_FEATURE_NOFLAGS) {
+            tcg_gen_addi_tl(cpu_R[rd], cpu_R[ra], sign_extend(I16, 16));
+        } else {
             if (I16 == 0) {
                 tcg_gen_mov_tl(cpu_R[rd], cpu_R[ra]);
             } else {
@@ -987,6 +996,9 @@ static void dec_misc(DisasContext *dc, uint32_t insn)
 
     case 0x28:    /* l.addic */
         LOG_DIS("l.addic r%d, r%d, %d\n", rd, ra, I16);
+        if (dc->cpufeature & OPENRISC_FEATURE_NOFLAGS) {
+            gen_illegal_exception(dc);
+        }
         {
             int lab = gen_new_label();
             TCGv_i64 ta = tcg_temp_new_i64();
@@ -1744,6 +1756,7 @@ static inline void 
gen_intermediate_code_internal(OpenRISCCPU *cpu,
     dc->j_state = JUMP_DYNAMIC;
     dc->j_target = 0;
     dc->flags = cpu->env.cpucfgr;
+    dc->cpufeature = cpu->feature;
     dc->mem_idx = cpu_mmu_index(&cpu->env);
     dc->synced_flags = dc->tb_flags = tb->flags;
     dc->delayed_branch = !!(dc->tb_flags & D_FLAG);
-- 
1.8.4.1