[aarch64-port-dev ] RFR(S/M): 8247766: [aarch64] guarantee(val < (1U << nbits)) failed: Field too big for insn

[Andrew Haley]

On 07/07/2020 12:17, Patric Hedlin wrote:
> C1 code generation for reading and writing stack-slots does not handle 
> large immediate offsets on aarch64. This patch will ensure that 
> immediate offsets are admissible for base+(immediate)offset encoding or, 
> if this is not the case, will enforce an explicit address calculation to 
> a scratch register. (Also correcting a small glitch in 9-bit signed 
> immediate encoding check.)
> 
> NOTE: Current patch includes (local) definitions of is_simm/9 and 
> is_uimm/12, for review purpose only. With JDK-8248901 these will move to 
> Assembler, and will not be included in the change-set.

Umm, OK. These functions seem too complicated: all you have to do is

    int64_t chk = val >> (nbits - 1);                                                                                                   |(gdb)
    guarantee (chk == -1 || chk == 0, "Field too big for insn");                                                                        |#9  0x0000ffffbcab5c30 in Compilation::compile_method (this=0xffff80b7dde8)

but the AArch64 part of it looks fine.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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