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This commit is contained in:
Andy McFadden 2021-08-21 11:19:16 -07:00
parent fc5f36885a
commit a7cc9d5a53
1 changed files with 6 additions and 3 deletions
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9
Asm65/OpDef.cs
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@ -326,12 +326,11 @@ namespace Asm65 {
/// <summary>
/// Flag update delegate, used for code flow analysis.
/// </summary>
/// <param name="prevFlags">Previous flags value.</param>
/// <param name="flags">Current flags, to be modified by delegate. For conditional
/// branches, this value will be used when the branch is not taken.</param>
/// <param name="immVal">Immediate mode value, if any. Value may be 0-255
/// for an 8-bit operand, or 0-65535 for a 16-bit operand, or -1 if this is
/// not an immediate-mode instruction.</param>
/// <param name="newFlags">New flags value. For conditional branches, this is
/// the value to use when the branch is not taken.</param>
/// <param name="branchTakenFlags">For conditional branches, this is the updated
/// value when the branch is taken.</param>
private delegate StatusFlags FlagUpdater(StatusFlags flags, int immVal,
@ -997,6 +996,10 @@ namespace Asm65 {
BaseMemEffect = MemoryEffect.None,
StatusFlagUpdater = delegate (StatusFlags flags, int immVal,
ref StatusFlags condBranchTakenFlags) {
// It's potentially useful to update Z here and in BPL. For example, if the
// branch succeeds, it's likely that whatever set N=1 also set Z=0. However,
// you can set Z independently with TRB/TSB and BIT #imm (and of course PHA/PLP).
// These things are rare, but its best to stick with what we know must be true.
condBranchTakenFlags.N = 1;
flags.N = 0;
return flags;