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comparison python/ppci/mem2reg.py @ 300:158068af716c

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yafm
author Windel Bouwman
date Tue, 03 Dec 2013 18:00:22 +0100
parents python/mem2reg.py@9417caea2eb3
children
comparison
equal deleted inserted replaced
299:674789d9ff37 300:158068af716c
1 import logging
2 from transform import FunctionPass
3 from ir import *
4
5 def isAllocPromotable(allocinst):
6 # Check if alloc value is only used by load and store operations.
7 assert type(allocinst) is Alloc
8 return all(type(use) in [Load, Store] for use in allocinst.value.used_by)
9
10
11 class Mem2RegPromotor(FunctionPass):
12 def promoteSingleBlock(self, ai):
13 v = ai.value
14 bb = ai.Block
15
16 # Replace all loads with the value:
17 loads = [i for i in v.used_by if isinstance(i, Load)]
18 stores = [i for i in v.used_by if isinstance(i, Store)]
19 stores.sort(key=lambda s: s.Position)
20 stores.reverse()
21
22 for load in loads:
23 idx = load.Position
24 # Search upwards:
25 for store in stores:
26 if store.Position < load.Position:
27 break
28 load.value.replaceby(store.value)
29 logging.debug('replaced {} with {}'.format(load, store.value))
30 bb.removeInstruction(load)
31
32 # Remove store instructions:
33 for store in stores:
34 sv = store.value
35 logging.debug('removing {}'.format(store))
36 bb.removeInstruction(store)
37 #assert sv.Used
38
39 # Remove alloca instruction:
40 assert not ai.value.Used, ai.value.used_by
41 bb.removeInstruction(ai)
42
43 def promote(self, ai):
44 # Find load operations and replace them with assignments
45 v = ai.value
46 if len(ai.value.UsedInBlocks) == 1:
47 self.promoteSingleBlock(ai)
48 return
49
50 loads = [i for i in v.used_by if isinstance(i, Load)]
51 stores = [i for i in v.used_by if isinstance(i, Store)]
52
53 # Each store instruction can be removed (later).
54 # Instead of storing the value, we use it
55 # where the load would have been!
56 replMap = {}
57 for store in stores:
58 replMap[store] = store.value
59
60 # for each load, track back what the defining store
61 # was.
62 for load in loads:
63 pass
64
65 def onFunction(self, f):
66 for bb in f.BasicBlocks:
67 allocs = [i for i in bb.Instructions if isinstance(i, Alloc)]
68 for i in allocs:
69 if isAllocPromotable(i):
70 self.promote(i)