From 69c916d2a8a99105400cd8c753ae23a16a6763ec Mon Sep 17 00:00:00 2001
From: Christian Speckner <christian.speckner@mayflower.de>
Date: Thu, 11 Jul 2024 22:40:00 +0200
Subject: [PATCH] BL / B.W encoding tests 6 fixes.

---
 src/emucore/elf/ElfUtil.cxx      |  6 ++---
 src/emucore/elf/EncodingTest.cxx | 40 +++++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/src/emucore/elf/ElfUtil.cxx b/src/emucore/elf/ElfUtil.cxx
index c786b0c00..daf0d4824 100644
--- a/src/emucore/elf/ElfUtil.cxx
+++ b/src/emucore/elf/ElfUtil.cxx
@@ -30,7 +30,7 @@ Int32 elfUtil::decode_B_BL(uInt32 opcode)
     const uInt32 imm11 = hw2 & 0x7ff;
     const uInt32 imm10 = hw1 & 0x3ff;
 
-    Int32 offset = imm11 | (imm10 << 11) | (i1 << 21) | (i2 << 22) | (s << 23);
+    Int32 offset = imm11 | (imm10 << 11) | (i2 << 21) | (i1 << 22) | (s << 23);
 
     offset <<= 8;
     offset >>= 7;
@@ -45,8 +45,8 @@ uInt32 elfUtil::encode_B_BL(Int32 offset, bool link)
   offset >>= 1;
 
   uInt8 s = (offset >> 23) & 0x01;
-  uInt8 j2 = ((~offset >> 22) ^ s) & 0x01;
-  uInt8 j1 = ((~offset >> 21) ^ s) & 0x01;
+  uInt8 j2 = ((~offset >> 21) ^ s) & 0x01;
+  uInt8 j1 = ((~offset >> 22) ^ s) & 0x01;
   uInt32 imm11 = offset & 0x7ff;
   uInt32 imm10 = (offset >> 11) & 0x3ff;
 
diff --git a/src/emucore/elf/EncodingTest.cxx b/src/emucore/elf/EncodingTest.cxx
index a24cec16e..17579ca4c 100644
--- a/src/emucore/elf/EncodingTest.cxx
+++ b/src/emucore/elf/EncodingTest.cxx
@@ -17,4 +17,42 @@
 
 #include <gtest/gtest.h>
 
-TEST(HelloWorld, Passes) {}
+#include "bspf.hxx"
+#include "ElfUtil.hxx"
+
+namespace {
+
+  struct Encoding {
+    Int32 offset;
+    uInt32 opcodeBL;
+    uInt32 opcodeB;
+  };
+
+  class EncodingTest: public testing::TestWithParam<Encoding> {};
+
+  TEST_P(EncodingTest, OffsetIsEncodedCorrectlyToBL) {
+    EXPECT_EQ(elfUtil::encode_B_BL(GetParam().offset - 4, true), GetParam().opcodeBL);
+  }
+
+  TEST_P(EncodingTest, OffsetIsEncodedCorrectlyToBW) {
+    EXPECT_EQ(elfUtil::encode_B_BL(GetParam().offset - 4, false), GetParam().opcodeB);
+  }
+
+  TEST_P(EncodingTest, OffsetIsDecodedCorrectlyFromBL) {
+    EXPECT_EQ(elfUtil::decode_B_BL(GetParam().opcodeBL), GetParam().offset - 4);
+  }
+
+  TEST_P(EncodingTest, OffsetIsDecodedCorrectlyFromB) {
+    EXPECT_EQ(elfUtil::decode_B_BL(GetParam().opcodeB), GetParam().offset - 4);
+  }
+
+  INSTANTIATE_TEST_SUITE_P(EncodingSuite, EncodingTest, testing::Values(
+    Encoding{.offset = 10, .opcodeBL = 0xf803f000, .opcodeB = 0xb803f000},
+    Encoding{.offset = 16777090, .opcodeBL = 0xd7bff3ff, .opcodeB = 0x97bff3ff},
+    Encoding{.offset = 8388606, .opcodeBL = 0xf7fdf3ff, .opcodeB = 0xb7fdf3ff},
+    Encoding{.offset = -10, .opcodeBL = 0xfff9f7ff, .opcodeB = 0xbff9f7ff},
+    Encoding{.offset = -16777090, .opcodeBL = 0xd03df400, .opcodeB = 0x903df400},
+    Encoding{.offset = -8388606, .opcodeBL = 0xdffff7ff, .opcodeB = 0x9ffff7ff}
+  ));
+
+}