On Fri, 5 Aug 2022 16:36:23 GMT, Smita Kamath <svkam...@openjdk.org> wrote:
> 8289552: Make intrinsic conversions between bit representations of half
> precision values and floats
src/hotspot/cpu/x86/assembler_x86.cpp line 1927:
> 1925: assert(VM_Version::supports_evex(), "");
> 1926: InstructionAttr attributes(vector_len, /* rex_w */ false, /*
> legacy_mode */ false, /* no_mask_reg */ true, /*uses_vl */ true);
> 1927: attributes.set_is_evex_instruction();
This instruction is supported on AVX (vex encoded) platform as well.
Please rename this as vcvtps2ph and update the check to include supports_evex
or supports_f16C. The is_evex_instruction check should then be remvoed.
src/hotspot/cpu/x86/assembler_x86.cpp line 1931:
> 1929: emit_int8((unsigned char)0x1D);
> 1930: emit_int8((unsigned char)(0xC0 | encode));
> 1931: emit_int8(imm8);
You could do emit_int24() here.
src/hotspot/cpu/x86/assembler_x86.cpp line 1937:
> 1935: assert(VM_Version::supports_evex(), "");
> 1936: InstructionAttr attributes(vector_len, /* rex_w */ false, /*
> legacy_mode */false, /* no_mask_reg */ true, /* uses_vl */ true);
> 1937: attributes.set_is_evex_instruction();
This instruction is supported on AVX (vex encoded) platform as well.
Please rename this as vcvtph2ps and update the check to include supports_evex
or supports_f16C. The is_evex_instruction check should then be remvoed.
src/hotspot/cpu/x86/x86.ad line 1686:
> 1684: case Op_ConvHF2F:
> 1685: if (!VM_Version::supports_evex() ||
> !VM_Version::supports_avx512vl()) {
> 1686: return false;
Please include supports_f16c here.
src/hotspot/cpu/x86/x86_64.ad line 11310:
> 11308:
> 11309: instruct convF2HF_reg_reg(rRegI dst, regF src, regF tmp) %{
> 11310: predicate(VM_Version::supports_evex());
The predicate could be removed as the check is fully done in
match_rule_supported.
src/hotspot/cpu/x86/x86_64.ad line 11313:
> 11311: effect(TEMP tmp);
> 11312: match(Set dst (ConvF2HF src));
> 11313: format %{ "evcvtps2ph $dst,$src" %}
It will be good to also show the tmp register in the format.
src/hotspot/cpu/x86/x86_64.ad line 11323:
> 11321:
> 11322: instruct convHF2F_reg_reg(regF dst, rRegI src) %{
> 11323: predicate(VM_Version::supports_evex());
The predicate could be removed as it is fully covered in the
match_rule_supported.
src/hotspot/share/opto/convertnode.cpp line 251:
> 249:
> //------------------------------Identity---------------------------------------
> 250: Node* ConvHF2FNode::Identity(PhaseGVN* phase) {
> 251: return (in(1)->Opcode() == Op_ConvF2HF) ? in(1)->in(1) : this;
We cannot do this optimization:
HF2F(F2HF(x)) != x
This is because precision and range both are lost when we convert F2HF.
src/hotspot/share/opto/convertnode.hpp line 150:
> 148: virtual const Type *bottom_type() const { return Type::FLOAT; }
> 149: virtual const Type* Value(PhaseGVN* phase) const;
> 150: virtual Node* Identity(PhaseGVN* phase);
The identity method could be removed from ConvHF2FNode
-------------
PR: https://git.openjdk.org/jdk/pull/9781
