Added inspection to warn about unexpected condition code unaffecting instructions before conditional instructions.

Extended documentation.
Bugfix in M68kDeadWriteInspection.

README.md

@@ -37,6 +37,70 @@ good enough" to get started, and I can return to demo coding with its current st
 - Structure view
 - Documentation provider for symbol definitions and mnemonics (listing available addressing modes etc.).
 
+### Inspections
+
+#### M68kSyntaxInspection - Assembly instruction validity
+
+Checks the validity of the current instruction. If an instruction is not recognized, you may get one of the following errors:
+
+- Instruction _mnemonic_ not supported on selected cpu (you won't get this currently as only MC68000 is supported)
+- No operands expected for _mnemonic_
+- Second operand _op_ unexpected for _mnemonic_
+- Unsupported addressing mode for _mnemonic_
+- Unsupported addressing mode _op_ for first operand of _mnemonic_
+- Unsupported addressing mode _op_ for second operand of _mnemonic_
+- Unsupported addressing modes for operands in this order for _mnemonic_ (try swapping)
+- Instruction _mnemonic_ is unsized (you tried to specify `.b`, `.w` or `.l`)
+- Operation size _(.b,.w,.l)_ unsupported for _mnemonic_
+- Operation size _(.b,.w,.l)_ unsupported (should be _(.b,.w,.l)_)
+
+#### M68kDeadWriteInspection - Dead writes to registers
+
+This inspection looks at register writes and tries to find instructions that renders a write moot because it was overwritten by another instruction before
+anything useful was done with it.
+
+Analysis is aborted at global labels, flow control instructions, directives
+(e.g. conditional assembly) and macros with the register names as parameter.
+
+The inspection tries to take condition code changing into account and puts out a weak warning if the statement merely changes condition codes before the
+contents of the register are overwritten. In this case, it is sometimes better to replace `move` by `tst`.
+
+#### M68kUnexpectedConditionalInstructionInspection - Unaffected condition codes before conditional instruction
+
+Especially for novice coders, it is not clear that some instructions do not affect the condition codes for a subsequent condition branch or `scc` instruction.
+`movea`, `adda` and `suba` come to my mind.
+
+The inspection will report such suspicious instruction sequences.
+
+However, this does not need to be a programming error. Advanced coders sometimes make use of the fact that instructions do not change condition codes and thus
+optimize the order of execution.
+
+### Documentation provider
+
+#### M68kSymbolDefinitionDocumentationProvider
+
+Provides the assigned value of a `=`, `set` or `equ` symbol definition when hovering over a symbol.
+
+#### M68kRegisterFlowDocumentationProvider
+
+When hovering over or placing the cursor at a data or address register, the documentation will scan through the instructions backwards and forwards and will
+show all read, changes of the register contents. It does this until an instruction is found that defines (sets) the contents of the register
+(according to the size of the instruction where the cursor was placed).
+
+The analysis ignores all code flow instructions and might be inaccurate for branches, macro use, etc. It also stops at global labels.
+
+The documentation will search up to 100 instructions in each direction, but only four when hovering over the register
+(so if you need the whole analysis, use the documentation window).
+
+#### M68kInstructionDocumentationProvider
+
+When hovering over a mnemonic, it will show a short description of the assembly instruction.
+
+For the documentation window, affected condition codes, allowed operation sizes and addressing modes are listed for the selected instruction
+(so only stuff from `cmpa` is listed when you're looking at a `cmp.w a0,a1` instruction).
+
+If the current statement has no valid syntax, the instruction details of all matching mnemonics will be shown instead.
+
 ## Known issues
 
 - `Find Usages` always shows _"Unclassified"_ though it shouldn't (?)
@@ -80,7 +144,8 @@ make it work with JUnit 5. Feel free to use the code (in package ```de.platon42.
 - Performance: Optimized mnemonic lookup.
 - Enhancement: Reworked Instruction Documentation provider, now shows condition codes.
 - Bugfix: In ISA `exg` is no longer treated as setting a definitive value.
-- New: Added inspection find dead writes to registers!
+- New: Added inspection to find dead writes to registers!
+- New: Added inspection to warn about unexpected condition code unaffecting instructions before conditional instructions.
 
 ### V0.4 (03-Aug-21)
 

build.gradle

@@ -66,7 +66,8 @@ patchPluginXml {
       <li>Performance: Optimized mnemonic lookup.
       <li>Enhancement: Reworked Instruction Documentation provider, now shows condition codes.
       <li>Bugfix: In ISA exg is no longer treated as setting a definitive value.
-      <li>New: Added inspection find dead writes to registers!
+      <li>New: Added inspection to find dead writes to registers!
+      <li>New: Added inspection to warn about unexpected condition code unaffecting instructions before conditional instructions.
     </ul>
   <h4>V0.4 (03-Aug-21)</h4>
     <ul>

src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kDeadWriteInspection.kt

@@ -19,8 +19,8 @@ class M68kDeadWriteInspection : AbstractBaseM68kLocalInspectionTool() {
     companion object {
         private const val DISPLAY_NAME = "Dead writes to registers"
 
-        private const val DEAD_WRITE_MSG = "Register %s is overwritten later without being used"
+        private const val DEAD_WRITE_MSG_TEMPLATE = "Register %s is overwritten later without being used"
-        private const val POSSIBLY_DEAD_WRITE_MSG = "Register %s is overwritten later (only CC evaluated?)"
+        private const val POSSIBLY_DEAD_WRITE_MSG_TEMPLATE = "Register %s is overwritten later (only CC evaluated?)"
     }
 
     override fun getDisplayName() = DISPLAY_NAME
@@ -69,7 +69,7 @@ class M68kDeadWriteInspection : AbstractBaseM68kLocalInspectionTool() {
                 val currAsmInstruction = PsiTreeUtil.getChildOfType(currStatement, M68kAsmInstruction::class.java) ?: continue
                 val (isaData, currAdrMode) = findExactIsaDataAndAllowedAdrModeForInstruction(currAsmInstruction) ?: continue
                 if (isaData.changesControlFlow) break
-                val testedCc = getConcreteTestedCcFromMnemonic(currAsmInstruction.asmOp.mnemonic, isaData, adrMode)
+                val testedCc = getConcreteTestedCcFromMnemonic(currAsmInstruction.asmOp.mnemonic, isaData, currAdrMode)
                 if (((testedCc and ccModification) > 0) && !ccOverwritten) ccTested = true
                 if (currAdrMode.affectedCc != 0) ccOverwritten = true
                 if (checkIfInstructionUsesRegister(currAsmInstruction, register)) {
@@ -89,7 +89,7 @@ class M68kDeadWriteInspection : AbstractBaseM68kLocalInspectionTool() {
                             manager.createProblemDescriptor(
                                 asmInstruction,
                                 asmInstruction,
-                                (if (ccTested) POSSIBLY_DEAD_WRITE_MSG else DEAD_WRITE_MSG).format(register.regname),
+                                (if (ccTested) POSSIBLY_DEAD_WRITE_MSG_TEMPLATE else DEAD_WRITE_MSG_TEMPLATE).format(register.regname),
                                 if (ccTested) ProblemHighlightType.WEAK_WARNING else ProblemHighlightType.WARNING,
                                 isOnTheFly
                             )

src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kUnexpectedConditionalInstructionInspection.kt

@@ -0,0 +1,54 @@
+package de.platon42.intellij.plugins.m68k.inspections
+
+import com.intellij.codeInspection.InspectionManager
+import com.intellij.codeInspection.ProblemDescriptor
+import com.intellij.codeInspection.ProblemHighlightType
+import com.intellij.psi.util.PsiTreeUtil
+import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findMatchingInstructions
+import de.platon42.intellij.plugins.m68k.psi.*
+import de.platon42.intellij.plugins.m68k.utils.M68kIsaUtil
+import de.platon42.intellij.plugins.m68k.utils.M68kIsaUtil.findExactIsaDataAndAllowedAdrModeForInstruction
+
+class M68kUnexpectedConditionalInstructionInspection : AbstractBaseM68kLocalInspectionTool() {
+
+    companion object {
+        private const val DISPLAY_NAME = "Unaffected condition codes before conditional instruction"
+
+        private const val UNAFFECTED_CONDITION_CODES_MSG_TEMPLATE = "Condition codes unaffected by instruction (%s - %s)"
+    }
+
+    override fun getDisplayName() = DISPLAY_NAME
+
+    override fun checkAsmInstruction(asmInstruction: M68kAsmInstruction, manager: InspectionManager, isOnTheFly: Boolean): Array<ProblemDescriptor>? {
+        val asmOp = asmInstruction.asmOp
+        if (asmInstruction.addressingModeList.isEmpty()) return emptyArray()
+
+        val isaDataCandidates = findMatchingInstructions(asmOp.mnemonic)
+        if (isaDataCandidates.isEmpty()) return emptyArray()
+        val (isaData, adrMode) = findExactIsaDataAndAllowedAdrModeForInstruction(asmInstruction) ?: return emptyArray()
+        if ((adrMode.affectedCc > 0) || (adrMode.testedCc > 0) || isaData.changesControlFlow) return emptyArray()
+
+        var currStatement = asmInstruction.parent as M68kStatement
+        while (true) {
+            currStatement = PsiTreeUtil.getNextSiblingOfType(currStatement, M68kStatement::class.java) ?: break
+            val globalLabel = PsiTreeUtil.findChildOfType(currStatement, M68kGlobalLabel::class.java)
+            if (globalLabel != null) break
+            if (PsiTreeUtil.findChildOfAnyType(currStatement, M68kMacroCall::class.java, M68kPreprocessorDirective::class.java) != null) break
+            val currAsmInstruction = PsiTreeUtil.getChildOfType(currStatement, M68kAsmInstruction::class.java) ?: continue
+            val (currIsaData, currAdrMode) = findExactIsaDataAndAllowedAdrModeForInstruction(currAsmInstruction) ?: break
+            val testedCc = M68kIsaUtil.getConcreteTestedCcFromMnemonic(currAsmInstruction.asmOp.mnemonic, currIsaData, currAdrMode)
+            if (testedCc == 0) break
+
+            return arrayOf(
+                manager.createProblemDescriptor(
+                    asmInstruction,
+                    asmInstruction,
+                    UNAFFECTED_CONDITION_CODES_MSG_TEMPLATE.format(isaData.mnemonic, isaData.description),
+                    ProblemHighlightType.WARNING,
+                    isOnTheFly
+                )
+            )
+        }
+        return emptyArray()
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -53,6 +53,9 @@
         <localInspection implementationClass="de.platon42.intellij.plugins.m68k.inspections.M68kDeadWriteInspection"
                          displayName="Dead writes to registers" groupName="M68k"
                          enabledByDefault="true" level="WARNING"/>
+        <localInspection implementationClass="de.platon42.intellij.plugins.m68k.inspections.M68kUnexpectedConditionalInstructionInspection"
+                         displayName="Unaffected condition codes before conditional instruction" groupName="M68k"
+                         enabledByDefault="true" level="WARNING"/>
     </extensions>
 
     <actions>

src/main/resources/inspectionDescriptions/M68kUnexpectedConditionalInstruction.html

@@ -0,0 +1,18 @@
+<html>
+<body>
+Usually, it is expected that an instruction checking the condition codes or using
+the condition codes is preceded by an instruction that actually affects the condition
+codes. This inspection checks that this is the case.
+
+For example, the 'movea' and 'adda' instructions (which can be (and are!) often written
+as 'move' and 'add') do not affect the condition codes and a conditional branch
+will not work as expected.
+
+However, this does not need to be a programming error. Advanced coders sometimes
+make use of the fact that instructions do not change condition codes and thus
+optimize the order of execution.
+
+<!-- tooltip end -->
+Analysis is terminated at the next global label, macrocall or preprocessor statement.
+</body>
+</html>

src/test/java/de/platon42/intellij/plugins/m68k/inspections/M68kUnexpectedConditionalInstructionInspectionTest.kt

@@ -0,0 +1,74 @@
+package de.platon42.intellij.plugins.m68k.inspections
+
+import com.intellij.testFramework.fixtures.CodeInsightTestFixture
+import de.platon42.intellij.jupiter.MyFixture
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+internal class M68kUnexpectedConditionalInstructionInspectionTest : AbstractInspectionTest() {
+
+    @Test
+    internal fun movea_causes_warning_when_used_for_conditional_branching(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.enableInspections(M68kUnexpectedConditionalInstructionInspection::class.java)
+        myFixture.configureByText(
+            "unexpectedcc.asm", """
+    move.l  d0,a1
+    bne.s   .cont
+    rts
+.cont
+        """
+        )
+        assertHighlightings(myFixture, 1, "Condition codes unaffected by instruction (movea - Move Address)")
+    }
+
+    @Test
+    internal fun no_warning_on_consecutive_conditional_branches(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.enableInspections(M68kUnexpectedConditionalInstructionInspection::class.java)
+        myFixture.configureByText(
+            "unexpectedcc.asm", """
+	move.b  P61_arplist(pc,d0),d0
+	beq.b   .arp0
+	bmi.b   .arp1
+        """
+        )
+        assertThat(myFixture.doHighlighting()).isEmpty()
+    }
+
+    @Test
+    internal fun no_warning_on_macro_call_inbetween(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.enableInspections(M68kUnexpectedConditionalInstructionInspection::class.java)
+        myFixture.configureByText(
+            "unexpectedcc.asm", """
+    move.l  pd_PalCurShamPalPtr(a4),a1
+    PALSTEPDOWN
+    bne.s   .loopline
+        """
+        )
+        assertThat(myFixture.doHighlighting()).isEmpty()
+    }
+
+    @Test
+    internal fun no_warning_flow_control_instruction(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.enableInspections(M68kUnexpectedConditionalInstructionInspection::class.java)
+        myFixture.configureByText(
+            "unexpectedcc.asm", """
+    bsr     foo
+    bne.s   .loopline
+        """
+        )
+        assertThat(myFixture.doHighlighting()).isEmpty()
+    }
+
+    @Test
+    internal fun warning_on_conditional_set_series_with_suba(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.enableInspections(M68kUnexpectedConditionalInstructionInspection::class.java)
+        myFixture.configureByText(
+            "unexpectedcc.asm", """
+    sub.l   a0,a0
+    seq     d0
+    sne     d1
+        """
+        )
+        assertHighlightings(myFixture, 1, "Condition codes unaffected by instruction (suba - Subtract Address)")
+    }
+}