tree 505e8d9327e6b69b62947fae659ca9639a5394bf
parent 7549326b940948f617f3623c42299ee71b3027be
author whitequark <whitequark@whitequark.org> 1526497788 +0000
committer whitequark <whitequark@whitequark.org> 1526497788 +0000

[OR1K] Add the EPCR special-purpose register to register state.

This makes it possible to unwind hardware exception stack frames,
which necessarily save every register and so need an extra column
for storing the return address. CFI for the exception handler could
then look as follows:

.globl exception_vector
exception_vector:
    .cfi_startproc
    .cfi_signal_frame
    .cfi_return_column 32
    l.addi  r1, r1, -0x100
    .cfi_def_cfa_offset 0x100
    l.sw    0x00(r1), r2
    .cfi_offset 2, 0x00-0x100
    l.sw    0x04(r1), r3
    .cfi_offset 3, 0x04-0x100
    l.sw    0x08(r1), r4
    .cfi_offset 4, 0x08-0x100
    l.mfspr r3, r0, SPR_EPCR_BASE
    l.sw    0x78(r1), r3
    .cfi_offset 32, 0x78-0x100
    l.jal   exception_handler
     l.nop
    l.lwz   r2, 0x00(r1)
    l.lwz   r3, 0x04(r1)
    l.lwz   r4, 0x08(r1)
    l.jr    r9
     l.nop
    .cfi_endproc

This register could, of course, also be accessed by the trace
callback or personality function, if so desired.

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@332513 91177308-0d34-0410-b5e6-96231b3b80d8