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VarAction2: Replace divs of powers of 2 with shifts where possible

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This commit is contained in:
Jonathan G Rennison
2022-05-25 03:49:29 +01:00
parent fad5973161
commit da629e4cfa
1 changed files with 18 additions and 1 deletions
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19
src/newgrf.cpp
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@@ -5703,7 +5703,7 @@ static void NewSpriteGroup(ByteReader *buf)
case DSGA_OP_XOR:
if (adjust.and_mask <= 1) inference = prev_inference & (~VA2AIF_PREV_TERNARY);
break;
case DSGA_OP_MUL:
case DSGA_OP_MUL: {
if ((prev_inference & VA2AIF_ONE_OR_ZERO) && adjust.variable == 0x1A && adjust.shift_num == 0) {
/* Found a ternary operator */
adjust.operation = DSGA_OP_TERNARY;
@@ -5739,8 +5739,17 @@ static void NewSpriteGroup(ByteReader *buf)
}
}
inference = VA2AIF_PREV_TERNARY;
break;
}
uint32 sign_bit = (1 << ((varsize * 8) - 1));
if ((prev_inference & VA2AIF_PREV_MASK_ADJUST) && (prev_inference & VA2AIF_SIGNED_NON_NEGATIVE) && adjust.variable == 0x1A && adjust.shift_num == 0 && (adjust.and_mask & sign_bit) == 0) {
/* Determine whether the result will be always non-negative */
if (((uint64)group->adjusts[group->adjusts.size() - 2].and_mask) * ((uint64)adjust.and_mask) < ((uint64)sign_bit)) {
inference |= VA2AIF_SIGNED_NON_NEGATIVE;
}
}
break;
}
case DSGA_OP_SCMP:
inference = VA2AIF_SIGNED_NON_NEGATIVE;
/* Convert to UCMP if possible to make other analysis operations easier */
@@ -5768,6 +5777,14 @@ static void NewSpriteGroup(ByteReader *buf)
break;
}
}
break;
case DSGA_OP_SDIV:
if ((prev_inference & VA2AIF_SIGNED_NON_NEGATIVE) && adjust.variable == 0x1A && adjust.shift_num == 0 && HasExactlyOneBit(adjust.and_mask)) {
/* Convert to a shift */
adjust.operation = DSGA_OP_SHR;
adjust.and_mask = FindFirstBit(adjust.and_mask);
inference |= VA2AIF_SIGNED_NON_NEGATIVE;
}
default:
break;
}