diff --git a/src/execution-engine-spec/instructions.adoc b/src/execution-engine-spec/instructions.adoc index 6892a2e..51d6be4 100644 --- a/src/execution-engine-spec/instructions.adoc +++ b/src/execution-engine-spec/instructions.adoc @@ -147,8 +147,19 @@ Assembler syntax:: + [source] ---- -ldr{cond} dst, [src, off] +ldr , [, ] ---- ++ +Where: +[horizontal] +cond::: Optional condition. +dst::: Destination register. +src::: Source register. +off::: + Optional offset immediate. + Must be a multiple of 4 and in the range 0-8188. + If omitted, then 0 is used. + Examples:: + [source] @@ -160,6 +171,50 @@ ldr.eq r5, [r4] ; If the last comparison resulted in an 'eq' condition status ; then reads a word from the memory address in r4 into r5. ; Else, does nothing. ---- + +Privileged instruction:: No. +Updates program state flags:: No. +Exceptions:: +[horizontal] + MemFault::: + If the memory address being accessed is invalid, non readable or not paged in. + The kernel may update the page table entries and re-execute the instruction without the user application being aware that it failed in the first place. + +====== LDRIRW: Load Register Immediate Pre-indexed with Write-back +Description:: + Increments the source register then reads a word from memory into the destination register. + The immediate offset `off` is added to the `src` register value before reading a word from memory into the `dst` register. +Encoding:: A-Type +Assembler syntax:: ++ +[source] +---- +ldr , ![, ] +---- ++ +Where: +[horizontal] +cond::: Optional condition. +dst::: Destination register. +src::: Source register. +off::: + Optional offset immediate. + Must be a multiple of 4 and in the range 0-8188. + If omitted, then 4 is used. + +Examples:: ++ +[source] +---- +ldr r1, ![r0] ; Increments r0 by 4 then reads a word from the memory address + ; in r0 into r1. +ldr r3, ![r2, 8] ; Increments r2 by 8 then reads a word from the memory address + ; in r2 into r3. +ldr.eq r5, ![r4] ; If the last comparison resulted in an 'eq' condition status, + ; then increments r4 by 4 and reads a word from the memory + ; address in r4 into r5. Else, does nothing. +---- + Privileged instruction:: No. Updates program state flags:: No. Exceptions::