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Re: flow-analysis and Offner's notes
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From: |
Matt Wette |
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Subject: |
Re: flow-analysis and Offner's notes |
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Date: |
Sat, 9 Jun 2018 06:34:49 -0700 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 |
On 06/08/2018 05:17 PM, Matt Wette wrote:
Andy Windo's blog on flow-analysis in Guile references Offner's "Notes
on Graph
Algorithms Used in Optimizing Compilers"? Anyone read this
manuscript? Lemma
2.2 says, in a flow-graph, if x>>z and y>>z, then either x>>y or
y>>x. The proof
uses the argument that the path from s, the start, to z has to include
both x and y.
I'm not seeing that. Consider a graph s->x, s->y, x->z and y->z. What
am I missing?
(another example, in figure 2.1 C>>K and B>>K but C and B are not
ordered.)
This example does not not qualify as C and B do not dominate K.
C dominates K iff every path from the start S to K goes through C.