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Clarify shift amount (arg2)

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Alex Beregszaszi 2017-04-23 15:43:43 +01:00
parent 27847a875d
commit d4f5382f51
1 changed files with 6 additions and 4 deletions
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EIPS/eip-145.md
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@ -4,7 +4,7 @@
Title: Bitwise shifting instructions in EVM Title: Bitwise shifting instructions in EVM
Author: Alex Beregszaszi, Paweł Bylica Author: Alex Beregszaszi, Paweł Bylica
Type: Standard Track Type: Standard Track
Category Core Category: Core
Status: Draft Status: Draft
Created: 2017-02-13 Created: 2017-02-13
@ -34,7 +34,8 @@ The `SHL` instruction (shift left) pops 2 values from the stack, `arg1` and `arg
``` ```
Notes: Notes:
- If the shift amount is greater or equal 256 the result is 0. - The shift amount (`arg2`) is interpreted as an unsigned number.
- If the shift amount (`arg2`) is greater or equal 256 the result is 0.
### `0x1c`: `SHR` (logical shift right) ### `0x1c`: `SHR` (logical shift right)
@ -45,7 +46,8 @@ arg1 udiv 2^arg2
``` ```
Notes: Notes:
- If the shift amount is greater or equal 256 the result is 0. - The shift amount (`arg2`) is interpreted as an unsigned number.
- If the shift amount (`arg2`) is greater or equal 256 the result is 0.
### `0x1d`: `SAR` (arithmetic shift right) ### `0x1d`: `SAR` (arithmetic shift right)
@ -56,7 +58,7 @@ arg1 sdiv 2^arg2
``` ```
Notes: Notes:
- `arg2` is interpreted as unsigned number. - The shift amount (`arg2`) is interpreted as an unsigned number.
- If the shift amount (`arg2`) is greater or equal 256 the result is 0 if `arg1` is non-negative or -1 if `arg1` is negative. - If the shift amount (`arg2`) is greater or equal 256 the result is 0 if `arg1` is non-negative or -1 if `arg1` is negative.
The cost of the shift instructions is set at `verylow` tier (3 gas). The cost of the shift instructions is set at `verylow` tier (3 gas).