Implementation of basic data flow analysis for PowerPC (#212)

* WIP implementation

* * Move flow analysis to dedicated file
* Show string constants inline
* Handle calls to MWCC "sled" helpers which otherwise disrupt flow analysis

* Run cargo insta review

* Apply clippy feedback

* Update more tests.

* Remove std use from ppc flow analysis

* Try to make wasm build work again

* More test changes

* Probably last wasm fix

* Formatting

* Fix WASM

* One more clippy thing

* Fixed display of float constants in a LFS or LFD instruction in case where there is a branch to the subsequent instruction with a different register value.

* On lines with a reloc, only hide Symbol type data flow values rather than all data flow values.

* Formatting

objdiff-core/src/obj/mod.rs

@@ -233,6 +233,19 @@ pub enum SymbolKind {
     Section,
 }
 
+#[derive(Debug)]
+pub enum FlowAnalysisValue {
+    Text(String),
+}
+
+pub trait FlowAnalysisResult: core::fmt::Debug + Send {
+    fn get_argument_value_at_address(
+        &self,
+        address: u64,
+        argument: u8,
+    ) -> Option<&FlowAnalysisValue>;
+}
+
 #[derive(Debug, Clone, Eq, PartialEq, Hash, Default)]
 pub struct Symbol {
     pub name: String,
@@ -260,6 +273,7 @@ pub struct Object {
     pub path: Option<std::path::PathBuf>,
     #[cfg(feature = "std")]
     pub timestamp: Option<filetime::FileTime>,
+    pub flow_analysis_results: BTreeMap<u64, Box<dyn FlowAnalysisResult>>,
 }
 
 impl Default for Object {
@@ -274,6 +288,7 @@ impl Default for Object {
             path: None,
             #[cfg(feature = "std")]
             timestamp: None,
+            flow_analysis_results: BTreeMap::<u64, Box<dyn FlowAnalysisResult>>::new(),
         }
     }
 }
@@ -312,6 +327,8 @@ impl Object {
     pub fn symbol_by_name(&self, name: &str) -> Option<usize> {
         self.symbols.iter().position(|symbol| symbol.section.is_some() && symbol.name == name)
     }
+
+    pub fn has_flow_analysis_result(&self) -> bool { !self.flow_analysis_results.is_empty() }
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]

objdiff-core/src/obj/read.rs

@@ -432,17 +432,18 @@ fn map_relocations(
     Ok(())
 }
 
-fn calculate_pooled_relocations(
-    arch: &dyn Arch,
-    sections: &mut [Section],
-    symbols: &[Symbol],
-) -> Result<()> {
-    for (section_index, section) in sections.iter_mut().enumerate() {
+fn perform_data_flow_analysis(obj: &mut Object, config: &DiffObjConfig) -> Result<()> {
+    // If neither of these settings are on, no flow analysis to perform
+    if !config.analyze_data_flow && !config.ppc_calculate_pool_relocations {
+        return Ok(());
+    }
+
+    let mut generated_relocations = Vec::<(usize, Vec<Relocation>)>::new();
+    for (section_index, section) in obj.sections.iter().enumerate() {
         if section.kind != SectionKind::Code {
             continue;
         }
-        let mut fake_pool_relocs = Vec::new();
-        for symbol in symbols {
+        for symbol in obj.symbols.iter() {
             if symbol.section != Some(section_index) {
                 continue;
             }
@@ -457,14 +458,32 @@ fn calculate_pooled_relocations(
                         symbol.address + symbol.size
                     )
                 })?;
-            fake_pool_relocs.append(&mut arch.generate_pooled_relocations(
-                symbol.address,
-                code,
-                &section.relocations,
-                symbols,
-            ));
+
+            // Optional pooled relocation computation
+            // Long view: This could be replaced by the full data flow analysis
+            // once that feature has stabilized.
+            if config.ppc_calculate_pool_relocations {
+                let relocations = obj.arch.generate_pooled_relocations(
+                    symbol.address,
+                    code,
+                    &section.relocations,
+                    &obj.symbols,
+                );
+                generated_relocations.push((section_index, relocations));
+            }
+
+            // Optional full data flow analysis
+            if config.analyze_data_flow {
+                obj.arch.data_flow_analysis(obj, symbol, code, &section.relocations).and_then(
+                    |flow_result| obj.flow_analysis_results.insert(symbol.address, flow_result),
+                );
+            }
         }
-        section.relocations.append(&mut fake_pool_relocs);
+    }
+    for (section_index, mut relocations) in generated_relocations {
+        obj.sections[section_index].relocations.append(&mut relocations);
+    }
+    for section in obj.sections.iter_mut() {
         section.relocations.sort_by_key(|r| r.address);
     }
     Ok(())
@@ -865,15 +884,12 @@ pub fn parse(data: &[u8], config: &DiffObjConfig) -> Result<Object> {
     let (mut symbols, symbol_indices) =
         map_symbols(arch.as_ref(), &obj_file, &sections, &section_indices, split_meta.as_ref())?;
     map_relocations(arch.as_ref(), &obj_file, &mut sections, &section_indices, &symbol_indices)?;
-    if config.ppc_calculate_pool_relocations {
-        calculate_pooled_relocations(arch.as_ref(), &mut sections, &symbols)?;
-    }
     parse_line_info(&obj_file, &mut sections, &section_indices, data)?;
     if config.combine_data_sections || config.combine_text_sections {
         combine_sections(&mut sections, &mut symbols, config)?;
     }
     arch.post_init(&sections, &symbols);
-    Ok(Object {
+    let mut obj = Object {
         arch,
         endianness: obj_file.endianness(),
         symbols,
@@ -883,7 +899,14 @@ pub fn parse(data: &[u8], config: &DiffObjConfig) -> Result<Object> {
         path: None,
         #[cfg(feature = "std")]
         timestamp: None,
-    })
+        flow_analysis_results: Default::default(),
+    };
+
+    // Need to construct the obj first so that we have a convinient package to
+    // pass to flow analysis. Then the flow analysis will mutate obj adding
+    // additional data to it.
+    perform_data_flow_analysis(&mut obj, config)?;
+    Ok(obj)
 }
 
 #[cfg(feature = "std")]