| Daniel Dunbar | bae383b | 2008-11-12 12:31:28 +0000 | [diff] [blame] | 1 | IRgen optimization opportunities. |
| 2 | |
| 3 | //===---------------------------------------------------------------------===// |
| 4 | |
| 5 | The common pattern of |
| 6 | -- |
| 7 | short x; // or char, etc |
| 8 | (x == 10) |
| 9 | -- |
| 10 | generates an zext/sext of x which can easily be avoided. |
| 11 | |
| 12 | //===---------------------------------------------------------------------===// |
| 13 | |
| 14 | Bitfields accesses can be shifted to simplify masking and sign |
| 15 | extension. For example, if the bitfield width is 8 and it is |
| 16 | appropriately aligned then is is a lot shorter to just load the char |
| 17 | directly. |
| 18 | |
| 19 | //===---------------------------------------------------------------------===// |
| Daniel Dunbar | 0b0fcd3 | 2008-11-27 03:47:29 +0000 | [diff] [blame] | 20 | |
| Daniel Dunbar | c84f424 | 2008-12-04 09:05:45 +0000 | [diff] [blame] | 21 | It may be worth avoiding creation of alloca's for formal arguments |
| 22 | for the common situation where the argument is never written to or has |
| 23 | its address taken. The idea would be to begin generating code by using |
| 24 | the argument directly and if its address is taken or it is stored to |
| 25 | then generate the alloca and patch up the existing code. |
| 26 | |
| 27 | In theory, the same optimization could be a win for block local |
| 28 | variables as long as the declaration dominates all statements in the |
| 29 | block. |
| 30 | |
| 31 | //===---------------------------------------------------------------------===// |
| 32 | |