optimization/8697: [IA64] Lost zero-extension

[schwab at suse dot de]

>Number:         8697
>Category:       optimization
>Synopsis:       [IA64] Lost zero-extension
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Sun Nov 24 15:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     schwab@suse.de
>Release:        3.2.1 20021021 (prerelease) (SuSE Linux)
>Organization:
>Environment:
System: Linux sykes 2.4.19-SMP #1 SMP Thu Nov 14 17:03:31 UTC 2002 ia64 unknown unknown GNU/Linux
Architecture: ia64

host: ia64-suse-linux-gnu
build: ia64-suse-linux-gnu
target: ia64-suse-linux-gnu
configured with: ../configure --enable-threads=posix --prefix=/usr --with-local-prefix=/usr/local --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/lib --enable-languages=c,c++,f77,objc,java,ada --enable-libgcj --with-gxx-include-dir=/usr/include/g++ --with-slibdir=/lib --with-system-zlib --enable-shared --enable-__cxa_atexit ia64-suse-linux
>Description:
The function output_move_const_into_data_reg is miscompiled due to a
lost zero extension during combine pass.

rotate.c.15.life has this:

(insn 33 95 34 (set (reg:SI 349)
        (rotate:SI (reg/v:SI 342)
            (const_int 16 [0x10]))) 189 {*rotlsi3_internal} (nil)
    (expr_list:REG_DEAD (reg/v:SI 342)
        (nil)))

(insn 34 33 36 (set (reg:DI 350)
        (zero_extend:DI (reg:SI 349))) 32 {zero_extendsidi2} (insn_list 33 (nil))
    (expr_list:REG_DEAD (reg:SI 349)
        (nil)))

But combine changes that to:

(insn 34 33 36 (set (subreg:SI (reg:DI 350) 0)
        (rotate:SI (reg/v:SI 342)
            (const_int 16 [0x10]))) 189 {*rotlsi3_internal} (nil)
    (expr_list:REG_DEAD (reg/v:SI 342)
        (nil)))

There is nothing that sets the upper 32 bits of reg 350.
>How-To-Repeat:
$ gcc -O rotate.c -da
$ ./a.out
Aborted
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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