LRA is not able to reload zero_extracted in-out operand with matched input
operand in the same way as strict_low_part in-out operand.  The patch
applies the strict_low_part workaround, where we allow LRA to generate
an instruction with non-matched input operand, which is split post reload
to the instruction that inserts non-matched input operand to an in-out
operand and the instruction that uses matched operand, also to
zero_extracted in-out operand case.

The generated code from the pr82524.c testcase improves from:

    movl    %esi, %ecx
    movl    %edi, %eax
    movsbl  %ch, %esi
    addl    %esi, %edx
    movb    %dl, %ah

to:
    movl    %edi, %eax
    movl    %esi, %ecx
    movb    %ch, %ah
    addb    %dl, %ah

The compiler is now also able to handle non-commutative operations:

    movl    %edi, %eax
    movl    %esi, %ecx
    movb    %ch, %ah
    subb    %dl, %ah

and unary operations:

    movl    %edi, %eax
    movl    %esi, %edx
    movb    %dh, %ah
    negb    %ah

The patch also robustifies split condition of the splitters to ensure that
only alternatives with unmatched operands are split.

    PR target/82524

gcc/ChangeLog:

    * config/i386/i386.md (*add<mode>_1_slp):
    Split insn only for unmatched operand 0.
    (*sub<mode>_1_slp): Ditto.
    (*<any_logic:code><mode>_1_slp): Merge pattern from "*and<mode>_1_slp"
    and "*<any_logic:code><mode>_1_slp" using any_logic code iterator.
    Split insn only for unmatched operand 0.
    (*neg<mode>1_slp): Split insn only for unmatched operand 0.
    (*one_cmpl<mode>_1_slp): Ditto.
    (*ashl<mode>3_1_slp): Ditto.
    (*<any_shiftrt:insn><mode>_1_slp): Ditto.
    (*<any_rotate:insn><mode>_1_slp): Ditto.
    (*addqi_ext<mode>_1): Redefine as define_insn_and_split.  Add
    alternative 1 and split insn after reload for unmatched operand 0.
    (*<plusminus:insn>qi_ext<mode>_2): Merge pattern from
    "*addqi_ext<mode>_2" and "*subqi_ext<mode>_2" using plusminus code
    iterator. Redefine as define_insn_and_split.  Add alternative 1
    and split insn after reload for unmatched operand 0.
    (*subqi_ext<mode>_1): Redefine as define_insn_and_split.  Add
    alternative 1 and split insn after reload for unmatched operand 0.
    (*<any_logic:code>qi_ext<mode>_0): Merge pattern from
    "*andqi_ext<mode>_0" and and "*<any_logic:code>qi_ext<mode>_0" using
    any_logic code iterator.
    (*<any_logic:code>qi_ext<mode>_1): Merge pattern from
    "*andqi_ext<mode>_1" and "*<any_logic:code>qi_ext<mode>_1" using
    any_logic code iterator. Redefine as define_insn_and_split.  Add
    alternative 1 and split insn after reload for unmatched operand 0.
    (*<any_logic:code>qi_ext<mode>_1_cc): Merge pattern from
    "*andqi_ext<mode>_1_cc" and "*xorqi_ext<mode>_1_cc" using any_logic
    code iterator. Redefine as define_insn_and_split.  Add alternative 1
    and split insn after reload for unmatched operand 0.
    (*<any_logic:code>qi_ext<mode>_2): Merge pattern from
    "*andqi_ext<mode>_2" and "*<any_or:code>qi_ext<mode>_2" using
    any_logic code iterator. Redefine as define_insn_and_split.  Add
    alternative 1 and split insn after reload for unmatched operand 0.
    (*<any_logic:code>qi_ext<mode>_3): Redefine as define_insn_and_split.
    Add alternative 1 and split insn after reload for unmatched operand 0.
    (*negqi_ext<mode>_1): Rename from "*negqi_ext<mode>_2".  Add
    alternative 1 and split insn after reload for unmatched operand 0.
    (*one_cmplqi_ext<mode>_1): Ditto.
    (*ashlqi_ext<mode>_1): Ditto.
    (*<any_shiftrt:insn>qi_ext<mode>_1): Ditto.

gcc/testsuite/ChangeLog:

    * gcc.target/i386/pr78904-1.c (test_sub): New test.
    * gcc.target/i386/pr78904-1a.c (test_sub): Ditto.
    * gcc.target/i386/pr78904-1b.c (test_sub): Ditto.
    * gcc.target/i386/pr78904-2.c (test_sub): Ditto.
    * gcc.target/i386/pr78904-2a.c (test_sub): Ditto.
    * gcc.target/i386/pr78904-2b.c (test_sub): Ditto.
    * gcc.target/i386/pr78952-4.c (test_sub): Ditto.
    * gcc.target/i386/pr82524.c: New test.
    * gcc.target/i386/pr82524-1.c: New test.
    * gcc.target/i386/pr82524-2.c: New test.
    * gcc.target/i386/pr82524-3.c: New test.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Uros.