target-mips: fix DSP overflow macro and affected routines

The previous implementation incorrectly used same macro to detect overflow
for addition and subtraction. This patch makes distinction between these
two, and creates separate macros. The affected routines are changed
accordingly.

This change also includes additions to the existing tests for SUBQ_S_PH and
SUBQ_S_W that would trigger the fixed issue, and it removes dead code from
the test file. The last test case in subq_s_w.c is a bug found/reported/
isolated by Klaus Peichl from Dolby.

Signed-off-by: Petar Jovanovic <petar.jovanovic@imgtec.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

3 files changed, 94 insertions, 54 deletions

diff --git a/target-mips/dsp_helper.c b/target-mips/dsp_helper.c
index 841f47b91d..ffa9396c4b 100644
--- a/target-mips/dsp_helper.c
+++ b/target-mips/dsp_helper.c
@@ -44,7 +44,8 @@ typedef union {
 
 /*** MIPS DSP internal functions begin ***/
 #define MIPSDSP_ABS(x) (((x) >= 0) ? x : -x)
-#define MIPSDSP_OVERFLOW(a, b, c, d) (!(!((a ^ b ^ -1) & (a ^ c) & d)))
+#define MIPSDSP_OVERFLOW_ADD(a, b, c, d) (~(a ^ b) & (a ^ c) & d)
+#define MIPSDSP_OVERFLOW_SUB(a, b, c, d) ((a ^ b) & (a ^ c) & d)
 
 static inline void set_DSPControl_overflow_flag(uint32_t flag, int position,
                                                 CPUMIPSState *env)
@@ -142,7 +143,7 @@ static inline int16_t mipsdsp_add_i16(int16_t a, int16_t b, CPUMIPSState *env)
 
     tempI = a + b;
 
-    if (MIPSDSP_OVERFLOW(a, b, tempI, 0x8000)) {
+    if (MIPSDSP_OVERFLOW_ADD(a, b, tempI, 0x8000)) {
         set_DSPControl_overflow_flag(1, 20, env);
     }
 
@@ -156,7 +157,7 @@ static inline int16_t mipsdsp_sat_add_i16(int16_t a, int16_t b,
 
     tempS = a + b;
 
-    if (MIPSDSP_OVERFLOW(a, b, tempS, 0x8000)) {
+    if (MIPSDSP_OVERFLOW_ADD(a, b, tempS, 0x8000)) {
         if (a > 0) {
             tempS = 0x7FFF;
         } else {
@@ -175,7 +176,7 @@ static inline int32_t mipsdsp_sat_add_i32(int32_t a, int32_t b,
 
     tempI = a + b;
 
-    if (MIPSDSP_OVERFLOW(a, b, tempI, 0x80000000)) {
+    if (MIPSDSP_OVERFLOW_ADD(a, b, tempI, 0x80000000)) {
         if (a > 0) {
             tempI = 0x7FFFFFFF;
         } else {
@@ -858,7 +859,7 @@ static inline uint16_t mipsdsp_sub_i16(int16_t a, int16_t b, CPUMIPSState *env)
     int16_t  temp;
 
     temp = a - b;
-    if (MIPSDSP_OVERFLOW(a, -b, temp, 0x8000)) {
+    if (MIPSDSP_OVERFLOW_SUB(a, b, temp, 0x8000)) {
         set_DSPControl_overflow_flag(1, 20, env);
     }
 
@@ -871,8 +872,8 @@ static inline uint16_t mipsdsp_sat16_sub(int16_t a, int16_t b,
     int16_t  temp;
 
     temp = a - b;
-    if (MIPSDSP_OVERFLOW(a, -b, temp, 0x8000)) {
-        if (a > 0) {
+    if (MIPSDSP_OVERFLOW_SUB(a, b, temp, 0x8000)) {
+        if (a >= 0) {
             temp = 0x7FFF;
         } else {
             temp = 0x8000;
@@ -889,8 +890,8 @@ static inline uint32_t mipsdsp_sat32_sub(int32_t a, int32_t b,
     int32_t  temp;
 
     temp = a - b;
-    if (MIPSDSP_OVERFLOW(a, -b, temp, 0x80000000)) {
-        if (a > 0) {
+    if (MIPSDSP_OVERFLOW_SUB(a, b, temp, 0x80000000)) {
+        if (a >= 0) {
             temp = 0x7FFFFFFF;
         } else {
             temp = 0x80000000;
@@ -1004,7 +1005,7 @@ static inline uint32_t mipsdsp_sub32(int32_t a, int32_t b, CPUMIPSState *env)
     int32_t temp;
 
     temp = a - b;
-    if (MIPSDSP_OVERFLOW(a, -b, temp, 0x80000000)) {
+    if (MIPSDSP_OVERFLOW_SUB(a, b, temp, 0x80000000)) {
         set_DSPControl_overflow_flag(1, 20, env);
     }
 
@@ -1017,7 +1018,7 @@ static inline int32_t mipsdsp_add_i32(int32_t a, int32_t b, CPUMIPSState *env)
 
     temp = a + b;
 
-    if (MIPSDSP_OVERFLOW(a, b, temp, 0x80000000)) {
+    if (MIPSDSP_OVERFLOW_ADD(a, b, temp, 0x80000000)) {
         set_DSPControl_overflow_flag(1, 20, env);
     }
 
@@ -2488,37 +2489,42 @@ DP_QH(dpsq_s_w_qh, 0, 1);
 #endif
 
 #define DP_L_W(name, is_add) \
-void helper_##name(uint32_t ac, target_ulong rs, target_ulong rt,     \
-                   CPUMIPSState *env)                                 \
-{                                                                     \
-    int32_t temp63;                                                   \
-    int64_t dotp, acc;                                                \
-    uint64_t temp;                                                    \
-                                                                      \
-    dotp = mipsdsp_mul_q31_q31(ac, rs, rt, env);                      \
-    acc = ((uint64_t)env->active_tc.HI[ac] << 32) |                   \
-          ((uint64_t)env->active_tc.LO[ac] & MIPSDSP_LLO);            \
-    if (!is_add) {                                                    \
-        dotp = -dotp;                                                 \
-    }                                                                 \
-                                                                      \
-    temp = acc + dotp;                                                \
-    if (MIPSDSP_OVERFLOW((uint64_t)acc, (uint64_t)dotp, temp,         \
-                         (0x01ull << 63))) {                          \
-        temp63 = (temp >> 63) & 0x01;                                 \
-        if (temp63 == 1) {                                            \
-            temp = (0x01ull << 63) - 1;                               \
-        } else {                                                      \
-            temp = 0x01ull << 63;                                     \
-        }                                                             \
-                                                                      \
-        set_DSPControl_overflow_flag(1, 16 + ac, env);                \
-    }                                                                 \
-                                                                      \
-    env->active_tc.HI[ac] = (target_long)(int32_t)                    \
-        ((temp & MIPSDSP_LHI) >> 32);                                 \
-    env->active_tc.LO[ac] = (target_long)(int32_t)                    \
-        (temp & MIPSDSP_LLO);                                         \
+void helper_##name(uint32_t ac, target_ulong rs, target_ulong rt,      \
+                   CPUMIPSState *env)                                  \
+{                                                                      \
+    int32_t temp63;                                                    \
+    int64_t dotp, acc;                                                 \
+    uint64_t temp;                                                     \
+    bool overflow;                                                     \
+                                                                       \
+    dotp = mipsdsp_mul_q31_q31(ac, rs, rt, env);                       \
+    acc = ((uint64_t)env->active_tc.HI[ac] << 32) |                    \
+          ((uint64_t)env->active_tc.LO[ac] & MIPSDSP_LLO);             \
+    if (is_add) {                                                      \
+        temp = acc + dotp;                                             \
+        overflow = MIPSDSP_OVERFLOW_ADD((uint64_t)acc, (uint64_t)dotp, \
+                                        temp, (0x01ull << 63));        \
+    } else {                                                           \
+        temp = acc - dotp;                                             \
+        overflow = MIPSDSP_OVERFLOW_SUB((uint64_t)acc, (uint64_t)dotp, \
+                                        temp, (0x01ull << 63));        \
+    }                                                                  \
+                                                                       \
+    if (overflow) {                                                    \
+        temp63 = (temp >> 63) & 0x01;                                  \
+        if (temp63 == 1) {                                             \
+            temp = (0x01ull << 63) - 1;                                \
+        } else {                                                       \
+            temp = 0x01ull << 63;                                      \
+        }                                                              \
+                                                                       \
+        set_DSPControl_overflow_flag(1, 16 + ac, env);                 \
+    }                                                                  \
+                                                                       \
+    env->active_tc.HI[ac] = (target_long)(int32_t)                     \
+        ((temp & MIPSDSP_LHI) >> 32);                                  \
+    env->active_tc.LO[ac] = (target_long)(int32_t)                     \
+        (temp & MIPSDSP_LLO);                                          \
 }
 
 DP_L_W(dpaq_sa_l_w, 1);
diff --git a/tests/tcg/mips/mips32-dsp/subq_s_ph.c b/tests/tcg/mips/mips32-dsp/subq_s_ph.c
index 8e36dadef9..64c89ebd51 100644
--- a/tests/tcg/mips/mips32-dsp/subq_s_ph.c
+++ b/tests/tcg/mips/mips32-dsp/subq_s_ph.c
@@ -12,7 +12,8 @@ int main()
     resultdsp = 0x01;
 
     __asm
-        ("subq_s.ph %0, %2, %3\n\t"
+        ("wrdsp $0\n\t"
+         "subq_s.ph %0, %2, %3\n\t"
          "rddsp %1\n\t"
          : "=r"(rd), "=r"(dsp)
          : "r"(rs), "r"(rt)
@@ -27,7 +28,24 @@ int main()
     resultdsp = 0x01;
 
     __asm
-        ("subq_s.ph %0, %2, %3\n\t"
+        ("wrdsp $0\n\t"
+         "subq_s.ph %0, %2, %3\n\t"
+         "rddsp %1\n\t"
+         : "=r"(rd), "=r"(dsp)
+         : "r"(rs), "r"(rt)
+        );
+    dsp = (dsp >> 20) & 0x01;
+    assert(dsp == resultdsp);
+    assert(rd  == result);
+
+    rs = 0x12340000;
+    rt = 0x87658000;
+    result    = 0x7FFF7FFF;
+    resultdsp = 0x01;
+
+    __asm
+        ("wrdsp $0\n\t"
+         "subq_s.ph %0, %2, %3\n\t"
          "rddsp %1\n\t"
          : "=r"(rd), "=r"(dsp)
          : "r"(rs), "r"(rt)
diff --git a/tests/tcg/mips/mips32-dsp/subq_s_w.c b/tests/tcg/mips/mips32-dsp/subq_s_w.c
index 09022e9c85..9d456a90f4 100644
--- a/tests/tcg/mips/mips32-dsp/subq_s_w.c
+++ b/tests/tcg/mips/mips32-dsp/subq_s_w.c
@@ -12,7 +12,8 @@ int main()
     resultdsp = 0x01;
 
     __asm
-        ("subq_s.w %0, %2, %3\n\t"
+        ("wrdsp $0\n\t"
+         "subq_s.w %0, %2, %3\n\t"
          "rddsp %1\n\t"
          : "=r"(rd), "=r"(dsp)
          : "r"(rs), "r"(rt)
@@ -24,10 +25,11 @@ int main()
     rs = 0x66666;
     rt = 0x55555;
     result    = 0x11111;
-    resultdsp = 0x01;
+    resultdsp = 0x0;
 
     __asm
-        ("subq_s.w %0, %2, %3\n\t"
+        ("wrdsp $0\n\t"
+         "subq_s.w %0, %2, %3\n\t"
          "rddsp %1\n\t"
          : "=r"(rd), "=r"(dsp)
          : "r"(rs), "r"(rt)
@@ -36,23 +38,37 @@ int main()
     assert(dsp == resultdsp);
     assert(rd  == result);
 
-
-#if 0
-    rs = 0x35555555;
-    rt = 0xf5555555;
-    result    = 0x80000000;
+    rs = 0x0;
+    rt = 0x80000000;
+    result    = 0x7FFFFFFF;
     resultdsp = 0x01;
 
     __asm
-        ("subq_s.w %0, %2, %3\n\t"
+        ("wrdsp $0\n\t"
+         "subq_s.w %0, %2, %3\n\t"
          "rddsp %1\n\t"
          : "=r"(rd), "=r"(dsp)
          : "r"(rs), "r"(rt)
         );
+    dsp = (dsp >> 20) & 0x01;
+    assert(dsp == resultdsp);
+    assert(rd  == result);
+
+    rs = 0x80000000;
+    rt = 0x80000000;
+    result    = 0;
+    resultdsp = 0x00;
 
+    __asm
+        ("wrdsp $0\n\t"
+         "subq_s.w %0, %2, %3\n\t"
+         "rddsp %1\n\t"
+         : "=r"(rd), "=r"(dsp)
+         : "r"(rs), "r"(rt)
+        );
     dsp = (dsp >> 20) & 0x01;
     assert(dsp == resultdsp);
     assert(rd  == result);
-#endif
+
     return 0;
 }