Merge pull request #307 from lioncash/usat16

armemu: Fix USAT16.

1 files changed, 20 insertions, 11 deletions

diff --git a/src/core/arm/interpreter/armemu.cpp b/src/core/arm/interpreter/armemu.cpp
index b9ac8b9ad..99fc6c45d 100644
--- a/src/core/arm/interpreter/armemu.cpp
+++ b/src/core/arm/interpreter/armemu.cpp
@@ -6192,18 +6192,27 @@ L_stm_s_takeabort:
                                         //ichfly
                                         //USAT16
                                 {
-                                        u8 tar = BITS(12, 15);
-                                        u8 src = BITS(0, 3);
-                                        u8 val = BITS(16, 19);
-                                        s16 a1 = (state->Reg[src]);
-                                        s16 a2 = (state->Reg[src] >> 0x10);
-                                        s16 max = 0xFFFF >> (16 - val);
-                                        if (max < a1) a1 = max;
-                                        if (max < a2) a2 = max;
-                                        u32 temp2 = ((u32)(a2)) << 0x10;
-                                        state->Reg[tar] = (a1 & 0xFFFF) | (temp2);
+                                        const u8 rd_idx = BITS(12, 15);
+                                        const u8 rn_idx = BITS(0, 3);
+                                        const u8 num_bits = BITS(16, 19);
+                                        const s16 max = 0xFFFF >> (16 - num_bits);
+                                        s16 rn_lo = (state->Reg[rn_idx]);
+                                        s16 rn_hi = (state->Reg[rn_idx] >> 16);
+                                        
+                                        if (max < rn_lo)
+                                                rn_lo = max;
+                                        else if (rn_lo < 0)
+                                                rn_lo = 0;
+
+                                        if (max < rn_hi)
+                                                rn_hi = max;
+                                        else if (rn_hi < 0)
+                                                rn_hi = 0;
+                                        
+                                        state->Reg[rd_idx] = (rn_lo & 0xFFFF) | ((rn_hi << 16) & 0xFFFF);
+                                        return 1;
                                 }
-                                return 1;
+
                                 default:
                                         break;
                         }