https://sourceware.org/bugzilla/show_bug.cgi?id=27099
Bug ID: 27099
Summary: [ARM] ISB instruction inside an IT block
Product: binutils
Version: 2.35.1
Status: UNCONFIRMED
Severity: minor
Priority: P2
Component: gas
Assignee: unassigned at sourceware dot org
Reporter: kordalski.wojciech at gmail dot com
Target Milestone: ---
Created attachment 13068
--> https://sourceware.org/bugzilla/attachment.cgi?id=13068&action=edit
The minimal example
During research of ARM Cortex-M3-based processor for our master thesis, we
found a bug (using a tool that generates random-but-correct sequences of
assembly instructions).
Minimal example:
.syntax unified
.cpu cortex-m3
.thumb
.align 2
.type f1, %function
.thumb_func
f1:
it eq
isbeq
The example compiles successfully (arm-none-eabi-as -o test.o test.s
-mcpu=cortex-m3) without any message emitted, but it should not.
The ARMv7-M Architecture Reference Manual states that ISB instruction inside an
IT block is unpredictable (see Section A7.7.38 IT, page A7-236).
The ARMv7-M Architecture Reference Manual can be downloaded from:
https://static.docs.arm.com/ddi0403/ed/DDI0403E_d_armv7m_arm.pdf
Expected behavior: assembler should emit a warning or error message.
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