[Bug target/70321] New: [6 Regression] STV generates less optimized code

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70321

            Bug ID: 70321
           Summary: [6 Regression] STV generates less optimized code
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: enkovich.gnu at gmail dot com, ubizjak at gmail dot com
  Target Milestone: ---
            Target: i386

[hjl@gnu-tools-1 bitwise-1]$ cat z.i
void
foo (long long ixi)
{
  if (ixi != 14348907)
    __builtin_abort ();
}
[hjl@gnu-tools-1 bitwise-1]$ make z.s z1.s
/export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -O2 -m32 -S -o z.s z.i
/export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -O2 -m32 -mno-stv -S -o z1.s
z.i
[hjl@gnu-tools-1 bitwise-1]$ cat z.s
        .file   "z.i"
        .text
        .p2align 4,,15
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        subl    $12, %esp
        .cfi_def_cfa_offset 16
        movl    20(%esp), %edx
        movl    16(%esp), %eax
        xorb    $0, %dh
        xorl    $14348907, %eax
        movl    %edx, %ecx
        orl     %eax, %ecx
        jne     .L5
        addl    $12, %esp
        .cfi_remember_state
        .cfi_def_cfa_offset 4
        ret
.L5:
        .cfi_restore_state
        call    abort
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .ident  "GCC: (GNU) 6.0.0 20160318 (experimental)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 bitwise-1]$ cat z1.s
        .file   "z.i"
        .text
        .p2align 4,,15
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        subl    $12, %esp
        .cfi_def_cfa_offset 16
        movl    16(%esp), %eax
        xorl    $14348907, %eax
        orl     20(%esp), %eax
        jne     .L5
        addl    $12, %esp
        .cfi_remember_state
        .cfi_def_cfa_offset 4
        ret
.L5:
        .cfi_restore_state
        call    abort
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .ident  "GCC: (GNU) 6.0.0 20160318 (experimental)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 bitwise-1]$ 

STV generates:

        movl    20(%esp), %edx
        movl    16(%esp), %eax
        xorb    $0, %dh
        xorl    $14348907, %eax
        movl    %edx, %ecx
        orl     %eax, %ecx

vs

        movl    16(%esp), %eax
        xorl    $14348907, %eax
        orl     20(%esp), %eax