Update FPU Unit Tests for Rounding Mode

- Add Control Word to Unit Tests for `FLDCW` and `FRNDINT` - Verify Different Rounding Modes in these Unit Test cases
mbbsemu · Aug 28, 2024 · 6040f78 · 6040f78
1 parent 56339ec
commit 6040f78
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Showing 4 changed files with 54 additions and 18 deletions.
diff --git a/MBBSEmu.Tests/CPU/FLDCW_Tests.cs b/MBBSEmu.Tests/CPU/FLDCW_Tests.cs
@@ -7,22 +7,41 @@ namespace MBBSEmu.Tests.CPU
 {
     public class FLDCW_Tests : CpuTestBase
     {
-        [Fact]
-        public void FLDCW_Test()
+        /// <summary>
+        ///     Loads the FPU Control Word from Memory and sets the FPU Control Word
+        ///
+        ///     We'll verify this by not only setting the Control Word, but also verify
+        ///     the Round Mode is set correctly
+        ///
+        ///     Rounding Flag Conversion:
+        ///     Rounding Mode = (ControlWord >> 10) &amp; 0x3;
+        ///     0 => MidpointRounding.ToEven
+        ///     1 => MidpointRounding.ToNegativeInfinity
+        ///     2 => MidpointRounding.ToPositiveInfinity
+        ///     3 => MidpointRounding.ToZero
+        /// </summary>
+        [Theory]
+        [InlineData(0x0000, MidpointRounding.ToEven)]
+        [InlineData(0x0400, MidpointRounding.ToNegativeInfinity)]
+        [InlineData(0x0800, MidpointRounding.ToPositiveInfinity)]
+        [InlineData(0x0C00, MidpointRounding.ToZero)]
+        public void FLDCW_Test(ushort controlWord, MidpointRounding roundingMode)
         {
             Reset();
             mbbsEmuCpuRegisters.Fpu.ControlWord = 0;
             CreateDataSegment(new ReadOnlySpan<byte>(), 2);
-            mbbsEmuMemoryCore.SetWord(2,0, 0xFFFF);
+            mbbsEmuMemoryCore.SetArray(2, 0, [0, 0, 0]); //Set some junk data ahead of the actual address
+            mbbsEmuMemoryCore.SetWord(2,3, controlWord);
             mbbsEmuCpuRegisters.DS = 2;
 
             var instructions = new Assembler(16);
-            instructions.fldcw(__word_ptr[0]);
+            instructions.fldcw(__word_ptr[3]);
             CreateCodeSegment(instructions);
 
             mbbsEmuCpuCore.Tick();
 
-            Assert.Equal(0xFFFF, mbbsEmuCpuRegisters.Fpu.ControlWord);
+            Assert.Equal(controlWord, mbbsEmuCpuRegisters.Fpu.ControlWord);
+            Assert.Equal(roundingMode, mbbsEmuCpuRegisters.Fpu.GetRoundingControl());
         }
     }
 }
diff --git a/MBBSEmu.Tests/CPU/FRNDINT_Tests.cs b/MBBSEmu.Tests/CPU/FRNDINT_Tests.cs
@@ -5,20 +5,40 @@ namespace MBBSEmu.Tests.CPU
 {
     public class FRNDINT_Tests : CpuTestBase
     {
+        /// <summary>
+        ///     Tests the FRNDINT Instruction which rounds the value in ST(0) to the nearest integer
+        ///
+        ///     We'll test this by setting the FPU Control Mode to Round to different modes and verify.
+        /// 
+        ///     Rounding Flag Conversion:
+        ///     Rounding Mode = (ControlWord >> 10) &amp; 0x3;
+        ///     0 => MidpointRounding.ToEven
+        ///     1 => MidpointRounding.ToNegativeInfinity
+        ///     2 => MidpointRounding.ToPositiveInfinity
+        ///     3 => MidpointRounding.ToZero
+        /// </summary>
+        /// <param name="ST0Value"></param>
+        /// <param name="expectedValue"></param>
         [Theory]
-        [InlineData(2.1d, 2d)]
-        [InlineData(0.1d, 0d)]
-        [InlineData(1.9d, 2d)]
-        [InlineData(-1.9d, -2d)]
-        [InlineData(0.5d, 0d)]
-        [InlineData(0.49999999d, 0d)]
-        public void FRNDINT_Test(double ST0Value, double expectedValue)
+        //Round to Even
+        [InlineData(1.5, 2.0, 0x0000)]
+        [InlineData(-1.5, -2.0, 0x0000)]
+        //Round to Negative Infinity
+        [InlineData(1.5, 1.0, 0x0400)]
+        [InlineData(-1.5, -2.0, 0x0400)]
+        //Round to Positive Infinity
+        [InlineData(1.5, 2.0, 0x0800)]
+        [InlineData(-1.5, -1.0, 0x0800)]
+        //Round to Zero
+        [InlineData(1.5, 1.0, 0x0C00)]
+        [InlineData(-1.5, -1.0, 0x0C00)]
+        public void FRNDINT_Test(double ST0Value, double expectedValue, ushort controlWord)
         {
             Reset();
             mbbsEmuCpuCore.FpuStack[mbbsEmuCpuRegisters.Fpu.GetStackTop()] = ST0Value;
 
             //Set FPU Control Word to set rounding to even
-            mbbsEmuCpuRegisters.Fpu.ControlWord = 0x0000000C;
+            mbbsEmuCpuRegisters.Fpu.ControlWord = controlWord;
 
             var instructions = new Assembler(16);
             instructions.frndint();

diff --git a/MBBSEmu/CPU/CpuRegisters.cs b/MBBSEmu/CPU/CpuRegisters.cs
@@ -89,6 +89,7 @@ public void SetPointer(FarPtr ptr)
         public void PopStackTop() => Registers.Fpu.PopStackTop();
         public void PushStackTop() => Registers.Fpu.PushStackTop();
         public void ClearExceptions() => Registers.Fpu.ClearExceptions();
+        public MidpointRounding GetRoundingControl() => Registers.Fpu.GetRoundingControl();
 
         /// <summary>
         ///     Overridden ToString() to display the current state of the CPU Registers

diff --git a/MBBSEmu/CPU/ICpuRegisters.cs b/MBBSEmu/CPU/ICpuRegisters.cs
@@ -10,20 +10,16 @@ namespace MBBSEmu.CPU
     public interface IFpuRegisters
     {
         ushort StatusWord { get; set; }
-
         ushort ControlWord { get; set; }
-
         void SetFlag(EnumFpuStatusFlags statusFlag);
         void ClearFlag(EnumFpuStatusFlags statusFlag);
-
         byte GetStackTop();
-
         void SetStackTop(byte value);
-
         int GetStackPointer(Register register);
         void PopStackTop();
         void PushStackTop();
         void ClearExceptions();
+        MidpointRounding GetRoundingControl();
     }
 
     /// <summary>