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accessing memory can't cost less than nothing

This commit is contained in:
Dustin Brody 2018-07-24 18:37:56 -07:00
parent 9f01223dd2
commit 85e1c39a83
2 changed files with 15 additions and 10 deletions
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10
VMTests.md
View File

@ -406,8 +406,8 @@ OK: 33/52 Fail: 4/52 Skip: 15/52
+ deadCode_1.json OK + deadCode_1.json OK
+ dupAt51becameMload.json OK + dupAt51becameMload.json OK
- extcodecopyMemExp.json Fail - extcodecopyMemExp.json Fail
- for_loop1.json Fail + for_loop1.json OK
- for_loop2.json Fail + for_loop2.json OK
+ gas0.json OK + gas0.json OK
+ gas1.json OK + gas1.json OK
+ gasOverFlow.json OK + gasOverFlow.json OK
@ -451,7 +451,7 @@ OK: 33/52 Fail: 4/52 Skip: 15/52
+ loop_stacklimit_1021.json OK + loop_stacklimit_1021.json OK
+ memory1.json OK + memory1.json OK
+ mloadError0.json OK + mloadError0.json OK
- mloadError1.json Fail + mloadError1.json OK
+ mloadMemExp.json OK + mloadMemExp.json OK
+ mloadOutOfGasError2.json OK + mloadOutOfGasError2.json OK
+ msize0.json OK + msize0.json OK
@ -472,7 +472,7 @@ OK: 33/52 Fail: 4/52 Skip: 15/52
+ pop0.json OK + pop0.json OK
+ pop1.json OK + pop1.json OK
+ return1.json OK + return1.json OK
- return2.json Fail + return2.json OK
+ sha3MemExp.json OK + sha3MemExp.json OK
+ sstore_load_0.json OK + sstore_load_0.json OK
+ sstore_load_1.json OK + sstore_load_1.json OK
@ -483,7 +483,7 @@ OK: 33/52 Fail: 4/52 Skip: 15/52
+ swapAt52becameMstore.json OK + swapAt52becameMstore.json OK
+ when.json OK + when.json OK
``` ```
OK: 134/145 Fail: 10/145 Skip: 1/145 OK: 138/145 Fail: 6/145 Skip: 1/145
## vmLogTest ## vmLogTest
```diff ```diff
+ log0_emptyMem.json OK + log0_emptyMem.json OK

15
nimbus/vm/interpreter/gas_costs.nim
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@ -124,24 +124,29 @@ template gasCosts(FeeSchedule: GasFeeSchedule, prefix, ResultGasCostsName: untyp
# Except when memLength = 0, where per eq (297), # Except when memLength = 0, where per eq (297),
# M(currentMemSize, f, l) = currentMemSize # M(currentMemSize, f, l) = currentMemSize
if memLength == 0: let
prev_words = currentMemSize.wordCount
new_words = (memOffset + memLength).wordCount
if memLength == 0 or new_words <= prev_words:
# Special subcase of memory-expansion cost # Special subcase of memory-expansion cost
# currentMemSize - currentMemSize = 0 # currentMemSize - currentMemSize = 0
# "Referencing a zero length range ... does not require memory to be extended # "Referencing a zero length range ... does not require memory to be extended
# to the beginning of the range." # to the beginning of the range."
#
# Also, don't credit EVM code for allocating memory
# then accessing lots of low memory. memoryGasCost,
# via go-ethereum, checks for this as special case.
return 0 return 0
let let
prev_words = currentMemSize.wordCount
prev_cost = prev_words * static(FeeSchedule[GasMemory]) + prev_cost = prev_words * static(FeeSchedule[GasMemory]) +
(prev_words ^ 2) shr 9 # div 512 (prev_words ^ 2) shr 9 # div 512
new_words = (memOffset + memLength).wordCount
new_cost = new_words * static(FeeSchedule[GasMemory]) + new_cost = new_words * static(FeeSchedule[GasMemory]) +
(new_words ^ 2) shr 9 # div 512 (new_words ^ 2) shr 9 # div 512
# TODO: add logging # TODO: add logging
result = new_cost - prev_cost result = max(new_cost - prev_cost, 0)
func `prefix all_but_one_64th`(gas: GasInt): GasInt {.inline.} = func `prefix all_but_one_64th`(gas: GasInt): GasInt {.inline.} =
## Computes all but 1/64th ## Computes all but 1/64th