From 593d4861851f5137f2834a2fbf34aed3be129bd0 Mon Sep 17 00:00:00 2001
From: Lephenixnoir <sebastien.michelland@protonmail.com>
Date: Mon, 15 Jan 2024 18:55:55 +0100
Subject: [PATCH] fxos: fix basic block duplication bug

---
 lib/function.cpp | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/lib/function.cpp b/lib/function.cpp
index 751d406..d7a5152 100644
--- a/lib/function.cpp
+++ b/lib/function.cpp
@@ -172,7 +172,8 @@ struct Superblock
 };
 
 // TODO: Unclear what the exit status of the superblock is in case of error
-static Superblock exploreSuperblock(Function &function, u32 entry, bool *error)
+static Superblock exploreSuperblock(Function &function,
+    std::vector<Superblock> const &blocks, u32 entry, bool *error)
 {
     Superblock sb;
     sb.addresses.reserve(32);
@@ -182,6 +183,7 @@ static Superblock exploreSuperblock(Function &function, u32 entry, bool *error)
     VirtualSpace &vspace = function.parentBinary().vspace();
     bool inDelaySlot = false;
     bool terminatorFound = false;
+    bool ranIntoAnotherBlock = false;
     u32 pc = entry;
 
     /* Determine how much space the vspace covers at this address to know if we
@@ -195,7 +197,11 @@ static Superblock exploreSuperblock(Function &function, u32 entry, bool *error)
         return sb;
     }
 
-    while(!terminatorFound || inDelaySlot) {
+    /* Break after either finding a terminator or finding an instruction
+       already explored as part of another superblock, unless we are in a delay
+       slot, because (1) delay slots go with terminators, (2) if another block
+       starts at the delay slot there will be trouble, so duplicate it. */
+    while((!terminatorFound && !ranIntoAnotherBlock) || inDelaySlot) {
         sb.addresses.push_back(pc);
 
         /* Read the next instruction from memory */
@@ -238,6 +244,13 @@ static Superblock exploreSuperblock(Function &function, u32 entry, bool *error)
         terminatorFound = terminatorFound || opcode.isBlockTerminator();
         inDelaySlot = !inDelaySlot && opcode.hasDelaySlot();
         pc += 2;
+
+        for(auto const &other: blocks) {
+            if(other.addresses[0] == pc) {
+                ranIntoAnotherBlock = true;
+                break;
+            }
+        }
     }
 
     if(*error)
@@ -289,7 +302,7 @@ bool Function::exploreFunctionAt(u32 functionAddress)
             continue;
 
         bool error = false;
-        Superblock sb = exploreSuperblock(*this, entry, &error);
+        Superblock sb = exploreSuperblock(*this, blocks, entry, &error);
 
         if(error)
             return false;