[Bug target/116104] [15 Regression] GCN vs. "[rtl-optimization/116037] Explicitly track if a destination was skipped in ext-dce"

[ams at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116104

--- Comment #4 from Andrew Stubbs <ams at gcc dot gnu.org> ---
The problem insn is this:

(insn 31 30 32 2 (set (reg:V2SI 711)
        (ashift:V2SI (reg:V2SI 161 v1)
            (const_vector:V2SI [
                    (const_int 3 [0x3]) repeated x2
                ])))
"/srv/data/ams/upB/gcn/src/gcc-mainline/libgcc/libgcc2.c":70:11 2043
{vashlv2si3}
     (expr_list:REG_DEAD (reg:V2SI 161 v1)
        (nil)))

That is, it shifts each element in a 2-element vector by 3 bits. This looks
like valid GCN code to me.

ext_dce does not seem to be handling the vector case.