shader/arithmetic: Implement FCMP

Compares the third operand with zero, then selects between the first and
second.

src/video_core/engines/shader_bytecode.h

@@ -1095,6 +1095,11 @@ union Instruction {
         BitField<55, 1, u64> ftz;
     } fset;
 
+    union {
+        BitField<47, 1, u64> ftz;
+        BitField<48, 4, PredCondition> cond;
+    } fcmp;
+
     union {
         BitField<49, 1, u64> bf;
         BitField<35, 3, PredCondition> cond;
@@ -1771,6 +1776,7 @@ public:
         ICMP_R,
         ICMP_CR,
         ICMP_IMM,
+        FCMP_R,
         MUFU,  // Multi-Function Operator
         RRO_C, // Range Reduction Operator
         RRO_R,
@@ -2074,6 +2080,7 @@ private:
             INST("0101110100100---", Id::HSETP2_R, Type::HalfSetPredicate, "HSETP2_R"),
             INST("0111111-0-------", Id::HSETP2_IMM, Type::HalfSetPredicate, "HSETP2_IMM"),
             INST("0101110100011---", Id::HSET2_R, Type::HalfSet, "HSET2_R"),
+            INST("010110111010----", Id::FCMP_R, Type::Arithmetic, "FCMP_R"),
             INST("0101000010000---", Id::MUFU, Type::Arithmetic, "MUFU"),
             INST("0100110010010---", Id::RRO_C, Type::Arithmetic, "RRO_C"),
             INST("0101110010010---", Id::RRO_R, Type::Arithmetic, "RRO_R"),

src/video_core/shader/decode/arithmetic.cpp

@@ -21,7 +21,7 @@ u32 ShaderIR::DecodeArithmetic(NodeBlock& bb, u32 pc) {
 
     Node op_a = GetRegister(instr.gpr8);
 
-    Node op_b = [&]() -> Node {
+    Node op_b = [&] {
         if (instr.is_b_imm) {
             return GetImmediate19(instr);
         } else if (instr.is_b_gpr) {
@@ -141,6 +141,15 @@ u32 ShaderIR::DecodeArithmetic(NodeBlock& bb, u32 pc) {
         SetRegister(bb, instr.gpr0, value);
         break;
     }
+    case OpCode::Id::FCMP_R: {
+        UNIMPLEMENTED_IF(instr.fcmp.ftz == 0);
+        Node op_c = GetRegister(instr.gpr39);
+        Node comp = GetPredicateComparisonFloat(instr.fcmp.cond, std::move(op_c), Immediate(0.0f));
+        SetRegister(
+            bb, instr.gpr0,
+            Operation(OperationCode::Select, std::move(comp), std::move(op_a), std::move(op_b)));
+        break;
+    }
     case OpCode::Id::RRO_C:
     case OpCode::Id::RRO_R:
     case OpCode::Id::RRO_IMM: {