2 files changed, 20 insertions, 4 deletions

diff --git a/src/shader_recompiler/backend/glasm/emit_glasm_instructions.h b/src/shader_recompiler/backend/glasm/emit_glasm_instructions.h
index 817001afb..52420c3c9 100644
--- a/src/shader_recompiler/backend/glasm/emit_glasm_instructions.h
+++ b/src/shader_recompiler/backend/glasm/emit_glasm_instructions.h
@@ -187,7 +187,8 @@ void EmitSelectU8(EmitContext& ctx, ScalarS32 cond, ScalarS32 true_value, Scalar
 void EmitSelectU16(EmitContext& ctx, ScalarS32 cond, ScalarS32 true_value, ScalarS32 false_value);
 void EmitSelectU32(EmitContext& ctx, IR::Inst& inst, ScalarS32 cond, ScalarS32 true_value,
                    ScalarS32 false_value);
-void EmitSelectU64(EmitContext& ctx, ScalarS32 cond, Register true_value, Register false_value);
+void EmitSelectU64(EmitContext& ctx, IR::Inst& inst, ScalarS32 cond, Register true_value,
+                   Register false_value);
 void EmitSelectF16(EmitContext& ctx, ScalarS32 cond, Register true_value, Register false_value);
 void EmitSelectF32(EmitContext& ctx, IR::Inst& inst, ScalarS32 cond, ScalarS32 true_value,
                    ScalarS32 false_value);
diff --git a/src/shader_recompiler/backend/glasm/emit_glasm_select.cpp b/src/shader_recompiler/backend/glasm/emit_glasm_select.cpp
index 8f9df8e23..cfde86047 100644
--- a/src/shader_recompiler/backend/glasm/emit_glasm_select.cpp
+++ b/src/shader_recompiler/backend/glasm/emit_glasm_select.cpp
@@ -29,9 +29,24 @@ void EmitSelectU32(EmitContext& ctx, IR::Inst& inst, ScalarS32 cond, ScalarS32 t
     ctx.Add("CMP.S {},{},{},{};", inst, cond, true_value, false_value);
 }
 
-void EmitSelectU64([[maybe_unused]] EmitContext& ctx, [[maybe_unused]] ScalarS32 cond,
-                   [[maybe_unused]] Register true_value, [[maybe_unused]] Register false_value) {
-    throw NotImplementedException("GLASM instruction");
+void EmitSelectU64(EmitContext& ctx, IR::Inst& inst, ScalarS32 cond, Register true_value,
+                   Register false_value) {
+    ctx.reg_alloc.InvalidateConditionCodes();
+    const Register ret{ctx.reg_alloc.LongDefine(inst)};
+    if (ret == true_value) {
+        ctx.Add("MOV.S.CC RC.x,{};"
+                "MOV.U64 {}.x(EQ.x),{};",
+                cond, ret, false_value);
+    } else if (ret == false_value) {
+        ctx.Add("MOV.S.CC RC.x,{};"
+                "MOV.U64 {}.x(NE.x),{};",
+                cond, ret, true_value);
+    } else {
+        ctx.Add("MOV.S.CC RC.x,{};"
+                "MOV.U64 {}.x(EQ.x),{};"
+                "MOV.U64 {}.x(NE.x),{};",
+                cond, ret, false_value, ret, true_value);
+    }
 }
 
 void EmitSelectF16([[maybe_unused]] EmitContext& ctx, [[maybe_unused]] ScalarS32 cond,