use bit manip instead of loops for ldm/stm

melonDS-emu · Aug 8, 2024 · f6b73de · f6b73de
1 parent 56638c8
commit f6b73de
Showing 1 changed file with 66 additions and 77 deletions.
diff --git a/src/ARMInterpreter_LoadStore.cpp b/src/ARMInterpreter_LoadStore.cpp
@@ -400,11 +400,7 @@ void A_LDM(ARM* cpu)
 
     if (!(cpu->CurInstr & (1<<23)))
     {
-        for (int i = 0; i < 16; i++)
-        {
-            if (cpu->CurInstr & (1<<i))
-                base -= 4;
-        }
+        base -= 4 * __builtin_popcount(cpu->CurInstr & 0xFFFF);
 
         if (cpu->CurInstr & (1<<21))
         {
@@ -418,16 +414,17 @@ void A_LDM(ARM* cpu)
     if ((cpu->CurInstr & (1<<22)) && !(cpu->CurInstr & (1<<15)))
         cpu->UpdateMode(cpu->CPSR, (cpu->CPSR&~0x1F)|0x10, true);
 
-    for (int i = 0; i < 15; i++)
+    u16 reglist = cpu->CurInstr & 0x7FFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (preinc) base += 4;
-            if (first) cpu->DataRead32 (base, &cpu->R[i]);
-            else       cpu->DataRead32S(base, &cpu->R[i]);
-            first = false;
-            if (!preinc) base += 4;
-        }
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
+
+        if (preinc) base += 4;
+        if (first) cpu->DataRead32 (base, &cpu->R[i]);
+        else       cpu->DataRead32S(base, &cpu->R[i]);
+        first = false;
+        if (!preinc) base += 4;
     }
 
     if (cpu->CurInstr & (1<<15))
@@ -479,11 +476,7 @@ void A_STM(ARM* cpu)
 
     if (!(cpu->CurInstr & (1<<23)))
     {
-        for (u32 i = 0; i < 16; i++)
-        {
-            if (cpu->CurInstr & (1<<i))
-                base -= 4;
-        }
+        base -= 4 * __builtin_popcount(cpu->CurInstr & 0xFFFF);
 
         if (cpu->CurInstr & (1<<21))
             cpu->R[baseid] = base;
@@ -503,26 +496,27 @@ void A_STM(ARM* cpu)
         cpu->UpdateMode(cpu->CPSR, (cpu->CPSR&~0x1F)|0x10, true);
     }
 
-    for (u32 i = 0; i < 16; i++)
+    u16 reglist = cpu->CurInstr & 0xFFFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (preinc) base += 4;
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
 
-            if (i == baseid && !isbanked)
-            {
-                if ((cpu->Num == 0) || (!(cpu->CurInstr & ((1<<i)-1))))
-                    first ? cpu->DataWrite32(base, oldbase) : cpu->DataWrite32S(base, oldbase);
-                else
-                    first ? cpu->DataWrite32(base, base) : cpu->DataWrite32S(base, base); // checkme
-            }
+        if (preinc) base += 4;
+
+        if (i == baseid && !isbanked)
+        {
+            if ((cpu->Num == 0) || (!(cpu->CurInstr & ((1<<i)-1))))
+                first ? cpu->DataWrite32(base, oldbase) : cpu->DataWrite32S(base, oldbase);
             else
-                first ? cpu->DataWrite32(base, cpu->R[i]) : cpu->DataWrite32S(base, cpu->R[i]);
+                first ? cpu->DataWrite32(base, base) : cpu->DataWrite32S(base, base); // checkme
+        }
+        else
+            first ? cpu->DataWrite32(base, cpu->R[i]) : cpu->DataWrite32S(base, cpu->R[i]);
 
-            first = false;
+        first = false;
 
-            if (!preinc) base += 4;
-        }
+        if (!preinc) base += 4;
     }
 
     if (cpu->CurInstr & (1<<22))
@@ -700,31 +694,23 @@ void T_LDR_SPREL(ARM* cpu)
 
 void T_PUSH(ARM* cpu)
 {
-    int nregs = 0;
     bool first = true;
 
-    for (int i = 0; i < 8; i++)
-    {
-        if (cpu->CurInstr & (1<<i))
-            nregs++;
-    }
-
-    if (cpu->CurInstr & (1<<8))
-        nregs++;
-
     u32 base = cpu->R[13];
-    base -= (nregs<<2);
+    base -= 4 * __builtin_popcount(cpu->CurInstr & 0x1FF);
+
     cpu->R[13] = base;
 
-    for (int i = 0; i < 8; i++)
+    u8 reglist = cpu->CurInstr & 0xFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (first) cpu->DataWrite32 (base, cpu->R[i]);
-            else       cpu->DataWrite32S(base, cpu->R[i]);
-            first = false;
-            base += 4;
-        }
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
+
+        if (first) cpu->DataWrite32 (base, cpu->R[i]);
+        else       cpu->DataWrite32S(base, cpu->R[i]);
+        first = false;
+        base += 4;
     }
 
     if (cpu->CurInstr & (1<<8))
@@ -741,15 +727,16 @@ void T_POP(ARM* cpu)
     u32 base = cpu->R[13];
     bool first = true;
 
-    for (int i = 0; i < 8; i++)
+    u8 reglist = cpu->CurInstr & 0xFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (first) cpu->DataRead32 (base, &cpu->R[i]);
-            else       cpu->DataRead32S(base, &cpu->R[i]);
-            first = false;
-            base += 4;
-        }
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
+
+        if (first) cpu->DataRead32 (base, &cpu->R[i]);
+        else       cpu->DataRead32S(base, &cpu->R[i]);
+        first = false;
+        base += 4;
     }
 
     if (cpu->CurInstr & (1<<8))
@@ -771,15 +758,16 @@ void T_STMIA(ARM* cpu)
     u32 base = cpu->R[(cpu->CurInstr >> 8) & 0x7];
     bool first = true;
 
-    for (int i = 0; i < 8; i++)
+    u8 reglist = cpu->CurInstr & 0xFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (first) cpu->DataWrite32 (base, cpu->R[i]);
-            else       cpu->DataWrite32S(base, cpu->R[i]);
-            first = false;
-            base += 4;
-        }
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
+
+        if (first) cpu->DataWrite32 (base, cpu->R[i]);
+        else       cpu->DataWrite32S(base, cpu->R[i]);
+        first = false;
+        base += 4;
     }
 
     // TODO: check "Rb included in Rlist" case
@@ -792,15 +780,16 @@ void T_LDMIA(ARM* cpu)
     u32 base = cpu->R[(cpu->CurInstr >> 8) & 0x7];
     bool first = true;
 
-    for (int i = 0; i < 8; i++)
+    u8 reglist = cpu->CurInstr & 0xFF;
+    while (reglist)
     {
-        if (cpu->CurInstr & (1<<i))
-        {
-            if (first) cpu->DataRead32 (base, &cpu->R[i]);
-            else       cpu->DataRead32S(base, &cpu->R[i]);
-            first = false;
-            base += 4;
-        }
+        int i = __builtin_ctz(reglist);
+        reglist ^= 1<<i;
+
+        if (first) cpu->DataRead32 (base, &cpu->R[i]);
+        else       cpu->DataRead32S(base, &cpu->R[i]);
+        first = false;
+        base += 4;
     }
 
     if (!(cpu->CurInstr & (1<<((cpu->CurInstr >> 8) & 0x7))))