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A fairly regular CopySlice simplification #366

Merged
merged 5 commits into from
Sep 7, 2023
Merged

A fairly regular CopySlice simplification #366

merged 5 commits into from
Sep 7, 2023

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msooseth
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Description

This simplifies away some of the ConcreteBuf when we CopySlice from a WriteWord+ConcreteBuf combo. If the ConcreteBuf is larger than what we will copy, the last parts of the ConcreteBuf is useless.

Without:

            (CopySlice
              srcOffset: 0x0
              dstOffset: 0x0
              size:      0x40
              src:
                (WriteWord
                  idx:
                    0x0
                  val:
                    (WAddr
                      (SymAddr "arg1")
                    )
                )
                (ConcreteBuf
                  Length: 96 (0x60) bytes
                  0000:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0010:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0020:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0030:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0040:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0050:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 80   ................
                )
            )
            (ConcreteBuf "")

With:

            (CopySlice
              srcOffset: 0x0
              dstOffset: 0x0
              size:      0x40
              src:
                (WriteWord
                  idx:
                    0x0
                  val:
                    (WAddr
                      (SymAddr "arg1")
                    )
                )
                (ConcreteBuf
                  Length: 64 (0x40) bytes
                  0000:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0010:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0020:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                  0030:   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00   ................
                )
            )

Notice that there was no need for all that 96B ConcreteBuf -- the CopySlice will cut it out anyway. So we only keep 64B, which is what CopySlice will copy.

Checklist

  • tested locally
  • added automated tests
  • updated the docs
  • updated the changelog

d-xo
d-xo approved these changes Aug 29, 2023
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could be a little more general maybe, but otherwise lgtm

src/EVM/Expr.hs Outdated Show resolved Hide resolved
@msooseth msooseth added the enhancement New feature or request label Aug 30, 2023
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msooseth commented Sep 1, 2023

I have now made it more general, let me know what you think! :)

d-xo
d-xo reviewed Sep 4, 2023
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src/EVM/Expr.hs Show resolved Hide resolved
d-xo
d-xo reviewed Sep 4, 2023
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src/EVM/Expr.hs
(WriteWord wOff value (ConcreteBuf buf)) dst)
-- Let's not deal with overflow
| n+sz >= n && n+sz >= sz = (CopySlice srcOff dstOff size
(WriteWord wOff value (ConcreteBuf simplifiedBuf)) dst)
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fine to merge as is, but wondering if we can have some recursive rewrites that work for buffers other than a single writeword over concretebuf?

d-xo
d-xo approved these changes Sep 4, 2023
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lgtm!

@msooseth msooseth merged commit 79d7a75 into main Sep 7, 2023
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@msooseth @d-xo