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predecode: Add more comments to row_predecode_rom and insn_code values

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This adds comments to row_predecode_rom to aid understanding how the
columns in the second half of the table are allocated to different
primary opcodes, and to the insn_code values to assist in locating the
code with a given numeric value.  No code change.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras 2022-08-04 15:25:06 +10:00
parent 6db626d245
commit 58e799b350
2 changed files with 35 additions and 31 deletions
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58
decode_types.vhdl
View File

@ -32,7 +32,7 @@ package decode_types is
-- comparisons of the insn_code for the instruction with a few constants.
type insn_code is (
-- The following instructions don't have an RB operand or access FPRs
INSN_illegal,
INSN_illegal, -- 0
INSN_fetch_fail,
INSN_addi,
INSN_addic,
@ -42,7 +42,7 @@ package decode_types is
INSN_addpcis,
INSN_addze,
INSN_andi_dot,
INSN_andis_dot,
INSN_andis_dot, -- 10
INSN_attn,
INSN_b,
INSN_bc,
@ -52,7 +52,7 @@ package decode_types is
INSN_cbcdtd,
INSN_cdtbcd,
INSN_cmpi,
INSN_cmpli,
INSN_cmpli, -- 20
INSN_cntlzw,
INSN_cntlzd,
INSN_cnttzw,
@ -62,7 +62,7 @@ package decode_types is
INSN_creqv,
INSN_crnand,
INSN_crnor,
INSN_cror,
INSN_cror, -- 30
INSN_crorc,
INSN_crxor,
INSN_darn,
@ -72,7 +72,7 @@ package decode_types is
INSN_extsw,
INSN_extswsli,
INSN_isync,
INSN_lbz,
INSN_lbz, -- 40
INSN_lbzu,
INSN_ld,
INSN_ldu,
@ -82,7 +82,7 @@ package decode_types is
INSN_lhzu,
INSN_lwa,
INSN_lwz,
INSN_lwzu,
INSN_lwzu, -- 50
INSN_mcrf,
INSN_mcrfs,
INSN_mcrxrx,
@ -92,7 +92,7 @@ package decode_types is
INSN_mtcrf,
INSN_mtfsb,
INSN_mtfsfi,
INSN_mtmsr,
INSN_mtmsr, -- 60
INSN_mtmsrd,
INSN_mtspr,
INSN_mulli,
@ -102,7 +102,7 @@ package decode_types is
INSN_oris,
INSN_popcntb,
INSN_popcntw,
INSN_popcntd,
INSN_popcntd, -- 70
INSN_prtyw,
INSN_prtyd,
INSN_rfid,
@ -112,7 +112,7 @@ package decode_types is
INSN_rldimi,
INSN_rlwimi,
INSN_rlwinm,
INSN_sc,
INSN_sc, -- 80
INSN_setb,
INSN_slbia,
INSN_sradi,
@ -122,7 +122,7 @@ package decode_types is
INSN_std,
INSN_stdu,
INSN_sth,
INSN_sthu,
INSN_sthu, -- 90
INSN_stw,
INSN_stwu,
INSN_subfic,
@ -132,7 +132,7 @@ package decode_types is
INSN_tdi,
INSN_tlbsync,
INSN_twi,
INSN_wait,
INSN_wait, -- 100
INSN_xori,
INSN_xoris,
@ -150,7 +150,7 @@ package decode_types is
INSN_and,
INSN_andc,
INSN_bperm,
INSN_cmp,
INSN_cmp, -- 120
INSN_cmpb,
INSN_cmpeqb,
INSN_cmpl,
@ -160,7 +160,7 @@ package decode_types is
INSN_dcbt,
INSN_dcbtst,
INSN_dcbz,
INSN_divd,
INSN_divd, -- 130
INSN_divdu,
INSN_divde,
INSN_divdeu,
@ -170,7 +170,7 @@ package decode_types is
INSN_divweu,
INSN_eqv,
INSN_icbi,
INSN_icbt,
INSN_icbt, -- 140
INSN_isel,
INSN_lbarx,
INSN_lbzcix,
@ -180,7 +180,7 @@ package decode_types is
INSN_ldbrx,
INSN_ldcix,
INSN_ldx,
INSN_ldux,
INSN_ldux, -- 150
INSN_lharx,
INSN_lhax,
INSN_lhaux,
@ -190,7 +190,7 @@ package decode_types is
INSN_lhzux,
INSN_lwarx,
INSN_lwax,
INSN_lwaux,
INSN_lwaux, -- 160
INSN_lwbrx,
INSN_lwzcix,
INSN_lwzx,
@ -200,7 +200,7 @@ package decode_types is
INSN_moduw,
INSN_modud,
INSN_mulhw,
INSN_mulhwu,
INSN_mulhwu, -- 170
INSN_mulhd,
INSN_mulhdu,
INSN_mullw,
@ -210,7 +210,7 @@ package decode_types is
INSN_or,
INSN_orc,
INSN_rldcl,
INSN_rldcr,
INSN_rldcr, -- 180
INSN_rlwnm,
INSN_slw,
INSN_sld,
@ -220,7 +220,7 @@ package decode_types is
INSN_srd,
INSN_stbcix,
INSN_stbcx,
INSN_stbx,
INSN_stbx, -- 190
INSN_stbux,
INSN_stdbrx,
INSN_stdcix,
@ -230,7 +230,7 @@ package decode_types is
INSN_sthbrx,
INSN_sthcix,
INSN_sthcx,
INSN_sthx,
INSN_sthx, -- 200
INSN_sthux,
INSN_stwbrx,
INSN_stwcix,
@ -240,7 +240,7 @@ package decode_types is
INSN_subf,
INSN_subfc,
INSN_subfe,
INSN_td,
INSN_td, -- 210
INSN_tlbie,
INSN_tlbiel,
INSN_tw,
@ -272,7 +272,7 @@ package decode_types is
INSN_stfdu,
INSN_stfs,
INSN_stfsu,
INSN_stfdux,
INSN_stfdux, -- 260
INSN_stfdx,
INSN_stfiwx,
INSN_stfsux,
@ -284,7 +284,7 @@ package decode_types is
INSN_lfs,
INSN_lfsu,
INSN_lfdx,
INSN_lfdux,
INSN_lfdux, -- 270
INSN_lfiwax,
INSN_lfiwzx,
INSN_lfsx,
@ -296,7 +296,7 @@ package decode_types is
INSN_fadd,
INSN_fadds,
INSN_fcfid,
INSN_fcfids,
INSN_fcfids, -- 280
INSN_fcfidu,
INSN_fcfidus,
INSN_fcmpo,
@ -306,7 +306,7 @@ package decode_types is
INSN_fctidz,
INSN_fctidu,
INSN_fctiduz,
INSN_fctiw,
INSN_fctiw, -- 290
INSN_fctiwz,
INSN_fctiwu,
INSN_fctiwuz,
@ -316,7 +316,7 @@ package decode_types is
INSN_fmrgew,
INSN_fmrgow,
INSN_fnabs,
INSN_fneg,
INSN_fneg, -- 300
INSN_fre,
INSN_fres,
INSN_frim,
@ -326,7 +326,7 @@ package decode_types is
INSN_frsp,
INSN_frsqrte,
INSN_frsqrtes,
INSN_fsqrt,
INSN_fsqrt, -- 310
INSN_fsqrts,
INSN_fsub,
INSN_fsubs,
@ -339,7 +339,7 @@ package decode_types is
INSN_318, INSN_319,
-- The following instructions access FRA, FRB (possibly) and FRC operands
INSN_fmul,
INSN_fmul, -- 320
INSN_fmuls,
INSN_fmadd,
INSN_fmadds,
@ -349,7 +349,7 @@ package decode_types is
INSN_fnmadds,
INSN_fnmsub,
INSN_fnmsubs,
INSN_fsel
INSN_fsel -- 330
);
constant INSN_first_rb : insn_code := INSN_add;

8
predecode.vhdl
View File

@ -389,6 +389,8 @@ architecture behaviour of predecoder is
-- fit into 2048 entries, the columns are remapped so that 16-24 are
-- stored here as 8-15; in other words the address bits are
-- 1, insn(10..6), 1, insn(5), insn(3..1)
-- Columns 16-17 here are opcode 19 columns 0-1
-- Columns 24-31 here are opcode 19 columns 16-23
2#1_10000_11000# => INSN_bcctr,
2#1_00000_11000# => INSN_bclr,
2#1_10001_11000# => INSN_bctar,
@ -405,15 +407,17 @@ architecture behaviour of predecoder is
2#1_00000_11010# => INSN_rfid,
-- Major opcode 59
-- Address bits are 1, insn(10..6), 1, 0, insn(3..1)
-- Only column 14 is valid here; columns 16-31 are handled in the major table
-- Column 14 is mapped to column 6 of the space which is
-- mostly used for opcode 19.
-- Column 14 is mapped to column 22.
-- Columns 20-23 here are opcode 59 columns 12-15
2#1_11010_10110# => INSN_fcfids,
2#1_11110_10110# => INSN_fcfidus,
-- Major opcode 63
-- Columns 0-15 are mapped here; columns 16-31 are in the major table.
-- Address bits are 1, insn(10:6), 0, insn(4:1)
-- Columns 0-15 here are opcode 63 columns 0-15
2#1_00000_00000# => INSN_fcmpu,
2#1_00001_00000# => INSN_fcmpo,
2#1_00010_00000# => INSN_mcrfs,