this patch adds support for new fussion in znver5 documented in the
optimization manual:

   The Zen5 microarchitecture adds support to fuse reg-reg MOV Instructions
   with certain ALU instructions. The following conditions need to be met for
   fusion to happen:
     - The MOV should be reg-reg mov with Opcode 0x89 or 0x8B
     - The MOV is followed by an ALU instruction where the MOV and ALU destination register match.
     - The ALU instruction may source only registers or immediate data. There cannot be any memory source.
     - The ALU instruction sources either the source or dest of MOV instruction.
     - If ALU instruction has 2 reg sources, they should be different.
     - The following ALU instructions can fuse with an older qualified MOV instruction:
       ADD ADC AND XOR OP SUB SBB INC DEC NOT SAL / SHL SHR SAR
       (I assume OP is OR)

I also increased issue rate from 4 to 6.  Theoretically znver5 can do more, but
with our model we can't realy use it.
Increasing issue rate to 8 leads to infinite loop in scheduler.

Finally, I also enabled fuse_alu_and_branch since it is supported by
znver5 (I think by earlier zens too).

New fussion pattern moves quite few instructions around in common code:
@@ -2210,13 +2210,13 @@
        .cfi_offset 3, -32
        leaq    63(%rsi), %rbx
        movq    %rbx, %rbp
+       shrq    $6, %rbp
+       salq    $3, %rbp
        subq    $16, %rsp
        .cfi_def_cfa_offset 48
        movq    %rdi, %r12
-       shrq    $6, %rbp
-       movq    %rsi, 8(%rsp)
-       salq    $3, %rbp
        movq    %rbp, %rdi
+       movq    %rsi, 8(%rsp)
        call    _Znwm
        movq    8(%rsp), %rsi
        movl    $0, 8(%r12)
@@ -2224,8 +2224,8 @@
        movq    %rax, (%r12)
        movq    %rbp, 32(%r12)
        testq   %rsi, %rsi
-       movq    %rsi, %rdx
        cmovns  %rsi, %rbx
+       movq    %rsi, %rdx
        sarq    $63, %rdx
        shrq    $58, %rdx
        sarq    $6, %rbx
which should help decoder bandwidth and perhaps also cache, though I was not
able to measure off-noise effect on SPEC.

gcc/ChangeLog:

	* config/i386/i386.h (TARGET_FUSE_MOV_AND_ALU): New tune.
	* config/i386/x86-tune-sched.cc (ix86_issue_rate): Updat for znver5.
	(ix86_adjust_cost): Add TODO about znver5 memory latency.
	(ix86_fuse_mov_alu_p): New.
	(ix86_macro_fusion_pair_p): Use it.
	* config/i386/x86-tune.def (X86_TUNE_FUSE_ALU_AND_BRANCH): Add ZNVER5.
	(X86_TUNE_FUSE_MOV_AND_ALU): New tune;