Shaders: Explicitly conform to PICA semantics in MAX/MIN

2 files changed, 10 insertions, 2 deletions

diff --git a/src/video_core/shader/shader_interpreter.cpp b/src/video_core/shader/shader_interpreter.cpp
index ae5a30441..69e4efa68 100644
--- a/src/video_core/shader/shader_interpreter.cpp
+++ b/src/video_core/shader/shader_interpreter.cpp
@@ -177,7 +177,10 @@ void RunInterpreter(UnitState<Debug>& state) {
                     if (!swizzle.DestComponentEnabled(i))
                         continue;
 
-                    dest[i] = std::max(src1[i], src2[i]);
+                    // NOTE: Exact form required to match NaN semantics to hardware:
+                    //   max(0, NaN) -> NaN
+                    //   max(NaN, 0) -> 0
+                    dest[i] = (src1[i] > src2[i]) ? src1[i] : src2[i];
                 }
                 Record<DebugDataRecord::DEST_OUT>(state.debug, iteration, dest);
                 break;
@@ -190,7 +193,10 @@ void RunInterpreter(UnitState<Debug>& state) {
                     if (!swizzle.DestComponentEnabled(i))
                         continue;
 
-                    dest[i] = std::min(src1[i], src2[i]);
+                    // NOTE: Exact form required to match NaN semantics to hardware:
+                    //   min(0, NaN) -> NaN
+                    //   min(NaN, 0) -> 0
+                    dest[i] = (src1[i] < src2[i]) ? src1[i] : src2[i];
                 }
                 Record<DebugDataRecord::DEST_OUT>(state.debug, iteration, dest);
                 break;
diff --git a/src/video_core/shader/shader_jit_x64.cpp b/src/video_core/shader/shader_jit_x64.cpp
index e56bff2b8..456c8567d 100644
--- a/src/video_core/shader/shader_jit_x64.cpp
+++ b/src/video_core/shader/shader_jit_x64.cpp
@@ -467,6 +467,7 @@ void JitCompiler::Compile_FLR(Instruction instr) {
 void JitCompiler::Compile_MAX(Instruction instr) {
     Compile_SwizzleSrc(instr, 1, instr.common.src1, SRC1);
     Compile_SwizzleSrc(instr, 2, instr.common.src2, SRC2);
+    // SSE semantics match PICA200 ones: In case of NaN, SRC2 is returned.
     MAXPS(SRC1, R(SRC2));
     Compile_DestEnable(instr, SRC1);
 }
@@ -474,6 +475,7 @@ void JitCompiler::Compile_MAX(Instruction instr) {
 void JitCompiler::Compile_MIN(Instruction instr) {
     Compile_SwizzleSrc(instr, 1, instr.common.src1, SRC1);
     Compile_SwizzleSrc(instr, 2, instr.common.src2, SRC2);
+    // SSE semantics match PICA200 ones: In case of NaN, SRC2 is returned.
     MINPS(SRC1, R(SRC2));
     Compile_DestEnable(instr, SRC1);
 }