Force reciprocal operation with value biased by constant to be precise on macOS (#5110)

* Force operations to be precise in some cases on SPIR-V

* Make it a bit more strict, add comments

* Shader cache version bump

1 files changed, 25 insertions, 0 deletions

diff --git a/src/Ryujinx.Graphics.Shader/Translation/Rewriter.cs b/src/Ryujinx.Graphics.Shader/Translation/Rewriter.cs
index eab0f9d2..866ae522 100644
--- a/src/Ryujinx.Graphics.Shader/Translation/Rewriter.cs
+++ b/src/Ryujinx.Graphics.Shader/Translation/Rewriter.cs
@@ -14,6 +14,7 @@ namespace Ryujinx.Graphics.Shader.Translation
         public static void RunPass(HelperFunctionManager hfm, BasicBlock[] blocks, ShaderConfig config)
         {
             bool isVertexShader = config.Stage == ShaderStage.Vertex;
+            bool isImpreciseFragmentShader = config.Stage == ShaderStage.Fragment && config.GpuAccessor.QueryHostReducedPrecision();
             bool hasConstantBufferDrawParameters = config.GpuAccessor.QueryHasConstantBufferDrawParameters();
             bool hasVectorIndexingBug = config.GpuAccessor.QueryHostHasVectorIndexingBug();
             bool supportsSnormBufferTextureFormat = config.GpuAccessor.QueryHostSupportsSnormBufferTextureFormat();
@@ -45,6 +46,11 @@ namespace Ryujinx.Graphics.Shader.Translation
                         }
                     }
 
+                    if (isImpreciseFragmentShader)
+                    {
+                        EnableForcePreciseIfNeeded(operation);
+                    }
+
                     if (hasVectorIndexingBug)
                     {
                         InsertVectorComponentSelect(node, config);
@@ -81,6 +87,25 @@ namespace Ryujinx.Graphics.Shader.Translation
             }
         }
 
+        private static void EnableForcePreciseIfNeeded(Operation operation)
+        {
+            // There are some cases where a small bias is added to values to prevent division by zero.
+            // When operating with reduced precision, it is possible for this bias to get rounded to 0
+            // and cause a division by zero.
+            // To prevent that, we force those operations to be precise even if the host wants
+            // imprecise operations for performance.
+
+            if (operation.Inst == (Instruction.FP32 | Instruction.Divide) &&
+                operation.GetSource(0).Type == OperandType.Constant &&
+                operation.GetSource(0).AsFloat() == 1f &&
+                operation.GetSource(1).AsgOp is Operation addOp &&
+                addOp.Inst == (Instruction.FP32 | Instruction.Add) &&
+                addOp.GetSource(1).Type == OperandType.Constant)
+            {
+                addOp.ForcePrecise = true;
+            }
+        }
+
         private static void InsertVectorComponentSelect(LinkedListNode<INode> node, ShaderConfig config)
         {
             Operation operation = (Operation)node.Value;