[Bug ld/20030] New: STM32L4XX : --fix-stm32l4xx-629360 fails to create vldm/vpop veneers for double-precision registers

[christophe.monat at st dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20030

            Bug ID: 20030
           Summary: STM32L4XX : --fix-stm32l4xx-629360 fails to create
                    vldm/vpop veneers for double-precision registers
           Product: binutils
           Version: 2.27 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: christophe.monat at st dot com
  Target Milestone: ---

Created attachment 9228
  --> https://sourceware.org/bugzilla/attachment.cgi?id=9228&action=edit
Sequence of vldm/vpop with dp registers that should be patched by the linker.

The --fix-stm32l4xx-629360 ld option should create veneers for vldm/vpop
instructions when the number of words transferred is greater than 8.

This is the case for vldm/vpop when single precision register are used (eg in
the s0-s31 range), but not when the aliases to double precision registers are
used (eg the d0-d15 corresponding to s0-s31).

It turns out that, despite the fact that there is not much use for dp registers
in fpv4-sp-d16 mode, gcc uses dp sequences for generating its save/restore
sequences.

The original STM32L4XX hardware bug work-around fix did not account for that
case, an oversight.

To reproduce, use the attached .s file:
$ arm-none-eabi-as -EL -mcpu=cortex-m4 -mfpu=fpv4-sp-d16
stm32l4xx-fix-vldm-dp.s -o stm32l4xx-fix-vldm-dp.o
$ arm-none-eabi-ld -EL --fix-stm32l4xx-629360 -Ttext=0x8000
stm32l4xx-fix-vldm-dp.o -o stm32l4xx-fix-vldm-dp
$ arm-none-eabi-objdump -d stm32l4xx-fix-vldm-dp | grep veneer

is empty, this should not be the case since all instructions used are subject
to the bug.

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