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VarAction2: Detect and replace signed relational comparisons

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This commit is contained in:
Jonathan G Rennison
2022-05-25 23:58:44 +01:00
parent e732042785
commit 90a2aa57fc
3 changed files with 70 additions and 9 deletions
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55
src/newgrf.cpp
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@@ -5722,8 +5722,44 @@ static void NewSpriteGroup(ByteReader *buf)
} else {
switch (adjust.operation) {
case DSGA_OP_SMIN:
if (adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 1) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];
if (prev.operation == DSGA_OP_SCMP) {
prev.operation = DSGA_OP_SGE;
group->adjusts.pop_back();
inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
}
if (group->adjusts.size() >= 3 && prev.operation == DSGA_OP_XOR && prev.type == DSGA_TYPE_NONE && prev.variable == 0x1A &&
prev.shift_num == 0 && prev.and_mask == 2) {
DeterministicSpriteGroupAdjust &prev2 = group->adjusts[group->adjusts.size() - 3];
if (prev2.operation == DSGA_OP_SCMP) {
prev2.operation = DSGA_OP_SLE;
group->adjusts.pop_back();
group->adjusts.pop_back();
inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
}
}
}
if (adjust.and_mask <= 1 && (prev_inference & VA2AIF_SIGNED_NON_NEGATIVE)) inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
case DSGA_OP_SMAX:
if (adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 0) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];
if (group->adjusts.size() >= 3 && prev.operation == DSGA_OP_SUB && prev.type == DSGA_TYPE_NONE && prev.variable == 0x1A &&
prev.shift_num == 0 && prev.and_mask == 1) {
DeterministicSpriteGroupAdjust &prev2 = group->adjusts[group->adjusts.size() - 3];
if (prev2.operation == DSGA_OP_SCMP) {
prev2.operation = DSGA_OP_SGT;
group->adjusts.pop_back();
group->adjusts.pop_back();
inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
}
}
}
break;
case DSGA_OP_UMIN:
if (adjust.and_mask <= 1) inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
@@ -5737,7 +5773,7 @@ static void NewSpriteGroup(ByteReader *buf)
group->adjusts.pop_back();
break;
}
if ((prev_inference & VA2AIF_SIGNED_NON_NEGATIVE) && adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 1) {
if (adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 1) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];
if (prev.operation == DSGA_OP_SCMP || prev.operation == DSGA_OP_UCMP) {
prev.operation = DSGA_OP_EQ;
@@ -5753,7 +5789,18 @@ static void NewSpriteGroup(ByteReader *buf)
}
break;
case DSGA_OP_OR:
if (adjust.and_mask <= 1) inference = prev_inference & (VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO);
break;
case DSGA_OP_XOR:
if (adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 1) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];
if (prev.operation == DSGA_OP_SLT || prev.operation == DSGA_OP_SGE || prev.operation == DSGA_OP_SLE || prev.operation == DSGA_OP_SGT) {
prev.operation = (DeterministicSpriteGroupAdjustOperation)(prev.operation ^ 1);
group->adjusts.pop_back();
inference = VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO;
break;
}
}
if (adjust.and_mask <= 1) inference = prev_inference & (VA2AIF_SIGNED_NON_NEGATIVE | VA2AIF_ONE_OR_ZERO);
break;
case DSGA_OP_MUL: {
@@ -5804,12 +5851,6 @@ static void NewSpriteGroup(ByteReader *buf)
break;
}
case DSGA_OP_SCMP:
inference = VA2AIF_SIGNED_NON_NEGATIVE;
/* Convert to UCMP if possible to make other analysis operations easier */
if ((prev_inference & VA2AIF_SIGNED_NON_NEGATIVE) && adjust.variable == 0x1A && adjust.shift_num == 0 && (adjust.and_mask & get_sign_bit()) == 0) {
adjust.operation = DSGA_OP_UCMP;
}
break;
case DSGA_OP_UCMP:
inference = VA2AIF_SIGNED_NON_NEGATIVE;
break;