target-xtensa: implement windowed registers

See ISA, 4.7.1 for details.

Physical registers and currently visible window are separate fields in
CPUEnv. Only current window is accessible to TCG. On operations that
change window base helpers copy current window to and from physical
registers.

Window overflow check described in 4.7.1.3 is in separate patch.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 192 insertions, 0 deletions

diff --git a/target-xtensa/op_helper.c b/target-xtensa/op_helper.c
index 794a8340ca..7c3fb88a96 100644
--- a/target-xtensa/op_helper.c
+++ b/target-xtensa/op_helper.c
@@ -100,3 +100,195 @@ uint32_t HELPER(nsau)(uint32_t v)
 {
     return v ? clz32(v) : 32;
 }
+
+static void copy_window_from_phys(CPUState *env,
+        uint32_t window, uint32_t phys, uint32_t n)
+{
+    assert(phys < env->config->nareg);
+    if (phys + n <= env->config->nareg) {
+        memcpy(env->regs + window, env->phys_regs + phys,
+                n * sizeof(uint32_t));
+    } else {
+        uint32_t n1 = env->config->nareg - phys;
+        memcpy(env->regs + window, env->phys_regs + phys,
+                n1 * sizeof(uint32_t));
+        memcpy(env->regs + window + n1, env->phys_regs,
+                (n - n1) * sizeof(uint32_t));
+    }
+}
+
+static void copy_phys_from_window(CPUState *env,
+        uint32_t phys, uint32_t window, uint32_t n)
+{
+    assert(phys < env->config->nareg);
+    if (phys + n <= env->config->nareg) {
+        memcpy(env->phys_regs + phys, env->regs + window,
+                n * sizeof(uint32_t));
+    } else {
+        uint32_t n1 = env->config->nareg - phys;
+        memcpy(env->phys_regs + phys, env->regs + window,
+                n1 * sizeof(uint32_t));
+        memcpy(env->phys_regs, env->regs + window + n1,
+                (n - n1) * sizeof(uint32_t));
+    }
+}
+
+
+static inline unsigned windowbase_bound(unsigned a, const CPUState *env)
+{
+    return a & (env->config->nareg / 4 - 1);
+}
+
+static inline unsigned windowstart_bit(unsigned a, const CPUState *env)
+{
+    return 1 << windowbase_bound(a, env);
+}
+
+void xtensa_sync_window_from_phys(CPUState *env)
+{
+    copy_window_from_phys(env, 0, env->sregs[WINDOW_BASE] * 4, 16);
+}
+
+void xtensa_sync_phys_from_window(CPUState *env)
+{
+    copy_phys_from_window(env, env->sregs[WINDOW_BASE] * 4, 0, 16);
+}
+
+static void rotate_window_abs(uint32_t position)
+{
+    xtensa_sync_phys_from_window(env);
+    env->sregs[WINDOW_BASE] = windowbase_bound(position, env);
+    xtensa_sync_window_from_phys(env);
+}
+
+static void rotate_window(uint32_t delta)
+{
+    rotate_window_abs(env->sregs[WINDOW_BASE] + delta);
+}
+
+void HELPER(wsr_windowbase)(uint32_t v)
+{
+    rotate_window_abs(v);
+}
+
+void HELPER(entry)(uint32_t pc, uint32_t s, uint32_t imm)
+{
+    int callinc = (env->sregs[PS] & PS_CALLINC) >> PS_CALLINC_SHIFT;
+    if (s > 3 || ((env->sregs[PS] & (PS_WOE | PS_EXCM)) ^ PS_WOE) != 0) {
+        qemu_log("Illegal entry instruction(pc = %08x), PS = %08x\n",
+                pc, env->sregs[PS]);
+        HELPER(exception_cause)(pc, ILLEGAL_INSTRUCTION_CAUSE);
+    } else {
+        env->regs[(callinc << 2) | (s & 3)] = env->regs[s] - (imm << 3);
+        rotate_window(callinc);
+        env->sregs[WINDOW_START] |=
+            windowstart_bit(env->sregs[WINDOW_BASE], env);
+    }
+}
+
+void HELPER(window_check)(uint32_t pc, uint32_t w)
+{
+    uint32_t windowbase = windowbase_bound(env->sregs[WINDOW_BASE], env);
+    uint32_t windowstart = env->sregs[WINDOW_START];
+    uint32_t m, n;
+
+    if ((env->sregs[PS] & (PS_WOE | PS_EXCM)) ^ PS_WOE) {
+        return;
+    }
+
+    for (n = 1; ; ++n) {
+        if (n > w) {
+            return;
+        }
+        if (windowstart & windowstart_bit(windowbase + n, env)) {
+            break;
+        }
+    }
+
+    m = windowbase_bound(windowbase + n, env);
+    rotate_window(n);
+    env->sregs[PS] = (env->sregs[PS] & ~PS_OWB) |
+        (windowbase << PS_OWB_SHIFT) | PS_EXCM;
+    env->sregs[EPC1] = env->pc = pc;
+
+    if (windowstart & windowstart_bit(m + 1, env)) {
+        HELPER(exception)(EXC_WINDOW_OVERFLOW4);
+    } else if (windowstart & windowstart_bit(m + 2, env)) {
+        HELPER(exception)(EXC_WINDOW_OVERFLOW8);
+    } else {
+        HELPER(exception)(EXC_WINDOW_OVERFLOW12);
+    }
+}
+
+uint32_t HELPER(retw)(uint32_t pc)
+{
+    int n = (env->regs[0] >> 30) & 0x3;
+    int m = 0;
+    uint32_t windowbase = windowbase_bound(env->sregs[WINDOW_BASE], env);
+    uint32_t windowstart = env->sregs[WINDOW_START];
+    uint32_t ret_pc = 0;
+
+    if (windowstart & windowstart_bit(windowbase - 1, env)) {
+        m = 1;
+    } else if (windowstart & windowstart_bit(windowbase - 2, env)) {
+        m = 2;
+    } else if (windowstart & windowstart_bit(windowbase - 3, env)) {
+        m = 3;
+    }
+
+    if (n == 0 || (m != 0 && m != n) ||
+            ((env->sregs[PS] & (PS_WOE | PS_EXCM)) ^ PS_WOE) != 0) {
+        qemu_log("Illegal retw instruction(pc = %08x), "
+                "PS = %08x, m = %d, n = %d\n",
+                pc, env->sregs[PS], m, n);
+        HELPER(exception_cause)(pc, ILLEGAL_INSTRUCTION_CAUSE);
+    } else {
+        int owb = windowbase;
+
+        ret_pc = (pc & 0xc0000000) | (env->regs[0] & 0x3fffffff);
+
+        rotate_window(-n);
+        if (windowstart & windowstart_bit(env->sregs[WINDOW_BASE], env)) {
+            env->sregs[WINDOW_START] &= ~windowstart_bit(owb, env);
+        } else {
+            /* window underflow */
+            env->sregs[PS] = (env->sregs[PS] & ~PS_OWB) |
+                (windowbase << PS_OWB_SHIFT) | PS_EXCM;
+            env->sregs[EPC1] = env->pc = pc;
+
+            if (n == 1) {
+                HELPER(exception)(EXC_WINDOW_UNDERFLOW4);
+            } else if (n == 2) {
+                HELPER(exception)(EXC_WINDOW_UNDERFLOW8);
+            } else if (n == 3) {
+                HELPER(exception)(EXC_WINDOW_UNDERFLOW12);
+            }
+        }
+    }
+    return ret_pc;
+}
+
+void HELPER(rotw)(uint32_t imm4)
+{
+    rotate_window(imm4);
+}
+
+void HELPER(restore_owb)(void)
+{
+    rotate_window_abs((env->sregs[PS] & PS_OWB) >> PS_OWB_SHIFT);
+}
+
+void HELPER(movsp)(uint32_t pc)
+{
+    if ((env->sregs[WINDOW_START] &
+            (windowstart_bit(env->sregs[WINDOW_BASE] - 3, env) |
+             windowstart_bit(env->sregs[WINDOW_BASE] - 2, env) |
+             windowstart_bit(env->sregs[WINDOW_BASE] - 1, env))) == 0) {
+        HELPER(exception_cause)(pc, ALLOCA_CAUSE);
+    }
+}
+
+void HELPER(dump_state)(void)
+{
+    cpu_dump_state(env, stderr, fprintf, 0);
+}