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VarAction2: Detect and replace reverse subtract via temp storage

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This commit is contained in:
Jonathan G Rennison
2022-05-27 03:14:07 +01:00
parent 381aa04660
commit 145536e1fd
3 changed files with 18 additions and 0 deletions
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15
src/newgrf.cpp
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@@ -5739,6 +5739,21 @@ static void NewSpriteGroup(ByteReader *buf)
replace_with_constant_load(0);
} else {
switch (adjust.operation) {
case DSGA_OP_SUB:
if (adjust.variable == 0x7D && adjust.shift_num == 0 && adjust.and_mask == 0xFFFFFFFF) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];
if (group->adjusts.size() >= 3 && prev.operation == DSGA_OP_RST) {
const DeterministicSpriteGroupAdjust &prev2 = group->adjusts[group->adjusts.size() - 3];
if (prev2.operation == DSGA_OP_STO && prev2.type == DSGA_TYPE_NONE && prev2.variable == 0x1A &&
prev2.shift_num == 0 && prev2.and_mask == adjust.parameter) {
/* Convert: store, load var, subtract stored --> (dead) store, reverse subtract var */
prev.operation = DSGA_OP_RSUB;
group->adjusts.pop_back();
break;
}
}
}
break;
case DSGA_OP_SMIN:
if (adjust.variable == 0x1A && adjust.shift_num == 0 && adjust.and_mask == 1) {
DeterministicSpriteGroupAdjust &prev = group->adjusts[group->adjusts.size() - 2];

2
src/newgrf_spritegroup.cpp
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@@ -189,6 +189,7 @@ static U EvalAdjustT(const DeterministicSpriteGroupAdjust &adjust, ScopeResolver
case DSGA_OP_SGE: return ((S)last_value >= (S)value) ? 1 : 0;
case DSGA_OP_SLE: return ((S)last_value <= (S)value) ? 1 : 0;
case DSGA_OP_SGT: return ((S)last_value > (S)value) ? 1 : 0;
case DSGA_OP_RSUB: return value - last_value;
default: return value;
}
}
@@ -556,6 +557,7 @@ static const char *_dsg_op_special_names[] {
"SGE",
"SLE",
"SGT",
"RSUB",
};
static_assert(lengthof(_dsg_op_special_names) == DSGA_OP_SPECIAL_END - DSGA_OP_TERNARY);

1
src/newgrf_spritegroup.h
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@@ -168,6 +168,7 @@ enum DeterministicSpriteGroupAdjustOperation {
DSGA_OP_SGE, ///< (signed) a >= b ? 1 : 0,
DSGA_OP_SLE, ///< (signed) a <= b ? 1 : 0,
DSGA_OP_SGT, ///< (signed) a > b ? 1 : 0,
DSGA_OP_RSUB, ///< b - a
DSGA_OP_SPECIAL_END,
};