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[SystemZ] Update README git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188062 91177308-0d34-0410-b5e6-96231b3b80d8 Richard Sandiford 6 years ago
1 changed file(s) with 6 addition(s) and 16 deletion(s). Raw diff Collapse all Expand all
4646
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4848
49 We don't use the BRANCH ON COUNT or BRANCH ON INDEX families of instruction.
49 We don't use the BRANCH ON INDEX instructions.
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58 We don't use the condition code results of anything except comparisons.
59
60 Implementing this may need something more finely grained than the z_cmp
61 and z_ucmp that we have now. It might (or might not) also be useful to
62 have a mask of "don't care" values in conditional branches. For example,
63 integer comparisons never set CC to 3, so the bottom bit of the CC mask
64 isn't particularly relevant. JNLH and JE are equally good for testing
65 equality after an integer comparison, etc.
66
67 --
68
69 We don't use the LOAD AND TEST or TEST DATA CLASS instructions.
58 We don't use the TEST DATA CLASS instructions.
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79 We don't optimize block memory operations.
80
81 It's definitely worth using things like MVC, CLC, NC, XC and OC with
68 We don't optimize block memory operations, except using single MVCs
69 for memcpy.
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71 It's definitely worth using things like CLC, NC, XC and OC with
8272 constant lengths. MVCIN may be worthwhile too.
8373
8474 We should probably implement things like memcpy using MVC with EXECUTE.