From 954633bba2d71c8c745989292b3f1669ecc7f02b Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Thu, 2 Oct 2025 18:01:49 -0700
Subject: [PATCH] add opcode for swapping top two values on the stack

---
 src/eval/eval_interpret.c | 6 ++++++
 src/lib_rdi/rdi.c         | 3 ++-
 src/lib_rdi/rdi.h         | 6 ++++--
 src/rdi/rdi.mdesk         | 3 ++-
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/eval/eval_interpret.c b/src/eval/eval_interpret.c
index 4bc92189..38850f8c 100644
--- a/src/eval/eval_interpret.c
+++ b/src/eval/eval_interpret.c
@@ -841,6 +841,12 @@ e_interpret(String8 bytecode)
           case 8:{nval.u64 = bswap_u64(svals[0].u64);}break;
         }
       }break;
+
+      case RDI_EvalOp_Swap:
+      {
+        // TODO: add support for pushing multiple values onto the stack
+        NotImplemented;
+      }break;
     }
     
     // rjf: push
diff --git a/src/lib_rdi/rdi.c b/src/lib_rdi/rdi.c
index dc297153..943411a9 100644
--- a/src/lib_rdi/rdi.c
+++ b/src/lib_rdi/rdi.c
@@ -58,7 +58,7 @@ sizeof(RDI_NameMapNode),
 sizeof(RDI_U8),
 };
 
-RDI_U16 rdi_eval_op_ctrlbits_table[52] =
+RDI_U16 rdi_eval_op_ctrlbits_table[53] =
 {
 RDI_EVAL_CTRLBITS(0, 0, 0),
 RDI_EVAL_CTRLBITS(0, 0, 0),
@@ -111,6 +111,7 @@ RDI_EVAL_CTRLBITS(1, 1, 1),
 RDI_EVAL_CTRLBITS(4, 0, 0),
 RDI_EVAL_CTRLBITS(4, 0, 0),
 RDI_EVAL_CTRLBITS(8, 0, 0),
+RDI_EVAL_CTRLBITS(0, 2, 2),
 RDI_EVAL_CTRLBITS(0, 0, 0),
 };
 
diff --git a/src/lib_rdi/rdi.h b/src/lib_rdi/rdi.h
index 4d052bce..44da5f21 100644
--- a/src/lib_rdi/rdi.h
+++ b/src/lib_rdi/rdi.h
@@ -523,7 +523,8 @@ RDI_EvalOp_ByteSwap             = 47,
 RDI_EvalOp_CallSiteValue        = 48,
 RDI_EvalOp_PartialValue         = 49,
 RDI_EvalOp_PartialValueBit      = 50,
-RDI_EvalOp_COUNT                = 51,
+RDI_EvalOp_Swap                 = 51,
+RDI_EvalOp_COUNT                = 52,
 } RDI_EvalOpEnum;
 
 typedef RDI_U8 RDI_EvalTypeGroup;
@@ -1122,6 +1123,7 @@ X(ByteSwap)\
 X(CallSiteValue)\
 X(PartialValue)\
 X(PartialValueBit)\
+X(Swap)\
 
 #define RDI_EvalTypeGroup_XList \
 X(Other)\
@@ -1623,6 +1625,6 @@ RDI_PROC RDI_S32 rdi_eval_op_typegroup_are_compatible(RDI_EvalOp op, RDI_EvalTyp
 RDI_PROC RDI_U8 *rdi_explanation_string_from_eval_conversion_kind(RDI_EvalConversionKind kind, RDI_U64 *size_out);
 
 extern RDI_U16 rdi_section_element_size_table[44];
-extern RDI_U16 rdi_eval_op_ctrlbits_table[52];
+extern RDI_U16 rdi_eval_op_ctrlbits_table[53];
 
 #endif // RDI_H
diff --git a/src/rdi/rdi.mdesk b/src/rdi/rdi.mdesk
index d106d98d..6bbcfb95 100644
--- a/src/rdi/rdi.mdesk
+++ b/src/rdi/rdi.mdesk
@@ -1349,7 +1349,8 @@ RDI_EvalOpTable:
   {CallSiteValue   48      4 0 0}
   {PartialValue    49      4 0 0}
   {PartialValueBit 50      8 0 0}
-  {COUNT           51      0 0 0}
+  {Swap            51      0 2 2} // swaps the top two entries on the stack
+  {COUNT           52      0 0 0}
 }
 
 // NOTE(rjf): "ck" -> "conversion kind, when converted to type group", used in square matrix form