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target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs

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The following commits changed the code such that the fallback to MFSS for MFFSCRN,
MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:

  bf8adfd88b - target/ppc: Move mffscrn[i] to decodetree
  394c2e2fda - target/ppc: Move mffsce to decodetree
  3e5bce70ef - target/ppc: Move mffsl to decodetree

The hardware will handle them as a MFFS instruction as the code did previously.
This means applications that were segfaulting under qemu when encountering these
instructions which is used in glibc libm functions for example.

The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.

This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
as the hardware decoder would, fixing the segfaulting libm code. It doesn't have
the fallback for 3.0 onwards to match hardware behaviour.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Reviewed-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230510111913.1718734-1-richard.purdie@linuxfoundation.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
This commit is contained in:
Richard Purdie 2023-05-10 12:19:13 +01:00 • committed by Daniel Henrique Barboza
parent ac84b57b4d
commit 5260ecffd2
2 changed files with 29 additions and 13 deletions
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20
target/ppc/insn32.decode
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@ -390,13 +390,19 @@ SETNBCR 011111 ..... ..... ----- 0111100000 - @X_bi
### Move To/From FPSCR
MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
{
# Before Power ISA v3.0, MFFS bits 11~15 were reserved and should be ignored
MFFS_ISA207 111111 ..... ----- ----- 1001000111 . @X_t_rc
[
MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
]
}
### Decimal Floating-Point Arithmetic Instructions