RFR: 8339790: Support Intel APX setzucc instruction [v4]

[Sandhya Viswanathan]

On Fri, 13 Sep 2024 20:37:27 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> - Support APX variant of SETcc, which supports zero-upper semantics (full register writer). Sets the destination operand to 0 or 1 depending on the settings of the status flags (CF, SF, OF, ZF, and PF) in the EFLAGS register. The destination operand points to a byte register or a byte in memory. The
>> condition code suffix (cc) indicates the condition being tested for. Additionally, if ND = 1 and the destination is a GPR, then also set the upper 56 bits of the GPR to 0.
>> - This saves emitting an explicit MOVZX instruction after setCC.
>> - These new instructions are encoded using 4 byte Extended EVEX encoding.
>> 
>> Validation performed over stand alone test point using Intel SDE.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review comments resolution.

src/hotspot/cpu/x86/assembler_x86.cpp line 16052:

> 16050: 
> 16051:   // Encoding Format : eevex_prefix | opcode_cc | modrm
> 16052:   int encode = vex_prefix_and_encode(dst->encoding(), 0, 0, VEX_SIMD_F2, /* MAP4 */VEX_OPCODE_0F_3C, &attributes);

We could replace this with:
int encode = evex_prefix_and_encode_ndd(dst->encoding(), 0, 0, VEX_SIMD_F2, /* MAP4 */VEX_OPCODE_0F_3C, &attributes);

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 10426:

> 10424: 
> 10425: void MacroAssembler::setcc(Assembler::Condition comparison, Register dst) {
> 10426:   if (VM_Version::supports_apx_f()) {

We could check UseAPX here instead of VM_Version::supports_apx_f().

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20920#discussion_r1761638922
PR Review Comment: https://git.openjdk.org/jdk/pull/20920#discussion_r1761942325