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Default "smart PLP handling" to off

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The feature is mildly broken and, frankly, unreliable on its best
day.  Default it to off for new projects.
This commit is contained in:
Andy McFadden 2020-07-24 21:34:36 -07:00
parent 1e7a6620e0
commit 2a65457e19
3 changed files with 23 additions and 15 deletions
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32
SourceGen/CodeAnalysis.cs
View File

@ -799,24 +799,30 @@ namespace SourceGen {
/// <summary>
/// Attempts to guess what the flags will be after a PLP instruction.
/// </summary>
/// <remarks>
/// We're not tracking stack contents or register contents, so this just
/// generally won't work. However, there's a lot of code that uses PHP to
/// save the current state and PLP to restore it, so if we can find a nearby
/// PHP we can just grab from that.
///
/// Failing that, we mark all flags as "indeterminate" and let the user sort
/// out what it should be. It's unlikely to matter except for M/X flags on
/// the 65816.
///
/// The emulation flag is not part of the status register, even if we do carry
/// it around like one. The E-flag is always carried over from the previous
/// instruction.
/// </remarks>
/// <param name="plpOffset">Offset of PLP instruction.</param>
/// <returns>Best guess at status flags.</returns>
private StatusFlags GuessFlagsForPLP(int plpOffset) {
// We're not tracking stack contents or register contents, so this just
// generally won't work. However, there's a lot of code that uses PHP to
// save the current state and PLP to restore it, so if we can find a nearby
// PHP we can just grab from that.
//
// Failing that, we mark all flags as "indeterminate" and let the user sort
// out what it should be. It's unlikely to matter except for M/X flags on
// the 65816.
//
// The emulation flag is not part of the status register, even if we do carry
// it around like one. The E-flag is always carried over from the previous
// instruction.
StatusFlags flags = StatusFlags.AllIndeterminate;
if (mAnalysisParameters.SmartPlpHandling) {
// TODO: this is broken. In some cases we end up latching the result from the
// first visit only. When the PHP instruction gets updated, the subsequent
// instructions are only re-evaluated if the flags have changed. If we reach
// an instruction where the flags match, we stop looking forward, and might
// not re-visit the PLP.
int backOffsetLimit = plpOffset - 128; // arbitrary 128-byte reach
if (backOffsetLimit < 0) {
backOffsetLimit = 0;

2
SourceGen/ProjectProperties.cs
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@ -63,7 +63,7 @@ namespace SourceGen {
MinCharsForString = DataAnalysis.DEFAULT_MIN_STRING_LENGTH;
SeekNearbyTargets = true;
UseRelocData = false;
SmartPlpHandling = true;
SmartPlpHandling = false;
SmartPlbHandling = true;
}
public AnalysisParameters(AnalysisParameters src) {

4
SourceGen/RuntimeData/Help/settings.html
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@ -274,7 +274,9 @@ improve automatic operand formatting.</p>
the processor status flags from a nearby <code>PHP</code> when a
<code>PLP</code> is encountered. If not enabled, all flags are set to
"indeterminate" following a <code>PLP</code>, except for the M/X
flags on the 65816, which are left unmodified.</p>
flags on the 65816, which are left unmodified. (In practice this
approach doesn't seem to work all that well, so the setting is
un-checked by default.)</p>
<p>If "smart PLB handling" is checked, the analyzer will watch for
code patterns like <code>PLB</code> preceded by <code>PHK</code>,
and generate appropriate Data Bank Register changes. If not enabled,