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FPU: Implement frsqrte[s] and a test for frsqrte

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This implements frsqrte by table lookup.  We first normalize the input
if necessary and adjust so that the exponent is even, giving us a
mantissa value in the range [1.0, 4.0), which is then used to look up
an entry in a 768-entry table.  The 768 entries are appended to the
table for reciprocal estimates, giving a table of 1024 entries in
total.  frsqrtes is implemented identically to frsqrte.

The estimate supplied is accurate to 1 part in 1024 or better.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
pull/245/head
Paul Mackerras 4 years ago
parent e1bbb786c0
commit 394f993e75
5 changed files with 239 additions and 6 deletions
Show Stats Download Patch File Download Diff File

2
decode1.vhdl
Unescape Escape View File

@ -421,6 +421,7 @@ architecture behaviour of decode1 is
2#10101# => (FPU, OP_FPOP, FRA, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fadds 2#10101# => (FPU, OP_FPOP, FRA, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fadds
2#11000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fres 2#11000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fres
2#11001# => (FPU, OP_FPOP, FRA, NONE, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fmuls 2#11001# => (FPU, OP_FPOP, FRA, NONE, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- fmuls
2#11010# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- frsqrtes
others => illegal_inst others => illegal_inst
); );


@ -479,6 +480,7 @@ architecture behaviour of decode1 is
2#0111# => (FPU, OP_FPOP, FRA, FRB, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fsel 2#0111# => (FPU, OP_FPOP, FRA, FRB, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fsel
2#1000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fre 2#1000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fre
2#1001# => (FPU, OP_FPOP, FRA, NONE, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fmul 2#1001# => (FPU, OP_FPOP, FRA, NONE, FRC, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- fmul
2#1010# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- frsqrte
others => illegal_inst others => illegal_inst
); );



194
fpu.vhdl
Unescape Escape View File

@ -41,7 +41,7 @@ architecture behaviour of fpu is
DO_FCFID, DO_FCTI, DO_FCFID, DO_FCTI,
DO_FRSP, DO_FRI, DO_FRSP, DO_FRI,
DO_FADD, DO_FMUL, DO_FDIV, DO_FADD, DO_FMUL, DO_FDIV,
DO_FRE, DO_FRE, DO_FRSQRTE,
DO_FSEL, DO_FSEL,
FRI_1, FRI_1,
ADD_SHIFT, ADD_2, ADD_3, ADD_SHIFT, ADD_2, ADD_3,
@ -50,6 +50,7 @@ architecture behaviour of fpu is
LOOKUP, LOOKUP,
DIV_2, DIV_3, DIV_4, DIV_5, DIV_6, DIV_2, DIV_3, DIV_4, DIV_5, DIV_6,
FRE_1, FRE_1,
RSQRT_1,
INT_SHIFT, INT_ROUND, INT_ISHIFT, INT_SHIFT, INT_ROUND, INT_ISHIFT,
INT_FINAL, INT_CHECK, INT_OFLOW, INT_FINAL, INT_CHECK, INT_OFLOW,
FINISH, NORMALIZE, FINISH, NORMALIZE,
@ -98,11 +99,12 @@ architecture behaviour of fpu is
exp_cmp : std_ulogic; exp_cmp : std_ulogic;
add_bsmall : std_ulogic; add_bsmall : std_ulogic;
is_multiply : std_ulogic; is_multiply : std_ulogic;
is_sqrt : std_ulogic;
first : std_ulogic; first : std_ulogic;
count : unsigned(1 downto 0); count : unsigned(1 downto 0);
end record; end record;


type lookup_table is array(0 to 255) of std_ulogic_vector(17 downto 0); type lookup_table is array(0 to 1023) of std_ulogic_vector(17 downto 0);


signal r, rin : reg_type; signal r, rin : reg_type;


@ -160,6 +162,8 @@ architecture behaviour of fpu is
constant MULADD_A : std_ulogic_vector(1 downto 0) := "10"; constant MULADD_A : std_ulogic_vector(1 downto 0) := "10";


-- Inverse lookup table, indexed by the top 8 fraction bits -- Inverse lookup table, indexed by the top 8 fraction bits
-- The first 256 entries are the reciprocal (1/x) lookup table,
-- and the remaining 768 entries are the reciprocal square root table.
-- Output range is [0.5, 1) in 0.19 format, though the top -- Output range is [0.5, 1) in 0.19 format, though the top
-- bit isn't stored since it is always 1. -- bit isn't stored since it is always 1.
-- Each output value is the inverse of the center of the input -- Each output value is the inverse of the center of the input
@ -199,7 +203,109 @@ architecture behaviour of fpu is
18x"04321", 18x"040dd", 18x"03e9b", 18x"03c5c", 18x"03a1f", 18x"037e4", 18x"035ac", 18x"03376", 18x"04321", 18x"040dd", 18x"03e9b", 18x"03c5c", 18x"03a1f", 18x"037e4", 18x"035ac", 18x"03376",
18x"03142", 18x"02f11", 18x"02ce2", 18x"02ab5", 18x"0288b", 18x"02663", 18x"0243d", 18x"02219", 18x"03142", 18x"02f11", 18x"02ce2", 18x"02ab5", 18x"0288b", 18x"02663", 18x"0243d", 18x"02219",
18x"01ff7", 18x"01dd8", 18x"01bbb", 18x"019a0", 18x"01787", 18x"01570", 18x"0135b", 18x"01149", 18x"01ff7", 18x"01dd8", 18x"01bbb", 18x"019a0", 18x"01787", 18x"01570", 18x"0135b", 18x"01149",
18x"00f39", 18x"00d2a", 18x"00b1e", 18x"00914", 18x"0070c", 18x"00506", 18x"00302", 18x"00100" 18x"00f39", 18x"00d2a", 18x"00b1e", 18x"00914", 18x"0070c", 18x"00506", 18x"00302", 18x"00100",
-- 1/sqrt(x) lookup table
-- Input is in the range [1, 4), i.e. two bits to the left of the
-- binary point. Those 2 bits index the following 3 blocks of 256 values.
-- 1.0 ... 1.9999
18x"3fe00", 18x"3fa06", 18x"3f612", 18x"3f224", 18x"3ee3a", 18x"3ea58", 18x"3e67c", 18x"3e2a4",
18x"3ded2", 18x"3db06", 18x"3d73e", 18x"3d37e", 18x"3cfc2", 18x"3cc0a", 18x"3c85a", 18x"3c4ae",
18x"3c106", 18x"3bd64", 18x"3b9c8", 18x"3b630", 18x"3b29e", 18x"3af10", 18x"3ab86", 18x"3a802",
18x"3a484", 18x"3a108", 18x"39d94", 18x"39a22", 18x"396b6", 18x"3934e", 18x"38fea", 18x"38c8c",
18x"38932", 18x"385dc", 18x"3828a", 18x"37f3e", 18x"37bf6", 18x"378b2", 18x"37572", 18x"37236",
18x"36efe", 18x"36bca", 18x"3689a", 18x"36570", 18x"36248", 18x"35f26", 18x"35c06", 18x"358ea",
18x"355d4", 18x"352c0", 18x"34fb0", 18x"34ca4", 18x"3499c", 18x"34698", 18x"34398", 18x"3409c",
18x"33da2", 18x"33aac", 18x"337bc", 18x"334cc", 18x"331e2", 18x"32efc", 18x"32c18", 18x"32938",
18x"3265a", 18x"32382", 18x"320ac", 18x"31dd8", 18x"31b0a", 18x"3183e", 18x"31576", 18x"312b0",
18x"30fee", 18x"30d2e", 18x"30a74", 18x"307ba", 18x"30506", 18x"30254", 18x"2ffa4", 18x"2fcf8",
18x"2fa4e", 18x"2f7a8", 18x"2f506", 18x"2f266", 18x"2efca", 18x"2ed2e", 18x"2ea98", 18x"2e804",
18x"2e572", 18x"2e2e4", 18x"2e058", 18x"2ddce", 18x"2db48", 18x"2d8c6", 18x"2d646", 18x"2d3c8",
18x"2d14c", 18x"2ced4", 18x"2cc5e", 18x"2c9ea", 18x"2c77a", 18x"2c50c", 18x"2c2a2", 18x"2c038",
18x"2bdd2", 18x"2bb70", 18x"2b90e", 18x"2b6b0", 18x"2b454", 18x"2b1fa", 18x"2afa4", 18x"2ad4e",
18x"2aafc", 18x"2a8ac", 18x"2a660", 18x"2a414", 18x"2a1cc", 18x"29f86", 18x"29d42", 18x"29b00",
18x"298c2", 18x"29684", 18x"2944a", 18x"29210", 18x"28fda", 18x"28da6", 18x"28b74", 18x"28946",
18x"28718", 18x"284ec", 18x"282c4", 18x"2809c", 18x"27e78", 18x"27c56", 18x"27a34", 18x"27816",
18x"275fa", 18x"273e0", 18x"271c8", 18x"26fb0", 18x"26d9c", 18x"26b8a", 18x"2697a", 18x"2676c",
18x"26560", 18x"26356", 18x"2614c", 18x"25f46", 18x"25d42", 18x"25b40", 18x"2593e", 18x"25740",
18x"25542", 18x"25348", 18x"2514e", 18x"24f58", 18x"24d62", 18x"24b6e", 18x"2497c", 18x"2478c",
18x"2459e", 18x"243b0", 18x"241c6", 18x"23fde", 18x"23df6", 18x"23c10", 18x"23a2c", 18x"2384a",
18x"2366a", 18x"2348c", 18x"232ae", 18x"230d2", 18x"22efa", 18x"22d20", 18x"22b4a", 18x"22976",
18x"227a2", 18x"225d2", 18x"22402", 18x"22234", 18x"22066", 18x"21e9c", 18x"21cd2", 18x"21b0a",
18x"21944", 18x"2177e", 18x"215ba", 18x"213fa", 18x"21238", 18x"2107a", 18x"20ebc", 18x"20d00",
18x"20b46", 18x"2098e", 18x"207d6", 18x"20620", 18x"2046c", 18x"202b8", 18x"20108", 18x"1ff58",
18x"1fda8", 18x"1fbfc", 18x"1fa50", 18x"1f8a4", 18x"1f6fc", 18x"1f554", 18x"1f3ae", 18x"1f208",
18x"1f064", 18x"1eec2", 18x"1ed22", 18x"1eb82", 18x"1e9e4", 18x"1e846", 18x"1e6aa", 18x"1e510",
18x"1e378", 18x"1e1e0", 18x"1e04a", 18x"1deb4", 18x"1dd20", 18x"1db8e", 18x"1d9fc", 18x"1d86c",
18x"1d6de", 18x"1d550", 18x"1d3c4", 18x"1d238", 18x"1d0ae", 18x"1cf26", 18x"1cd9e", 18x"1cc18",
18x"1ca94", 18x"1c910", 18x"1c78c", 18x"1c60a", 18x"1c48a", 18x"1c30c", 18x"1c18e", 18x"1c010",
18x"1be94", 18x"1bd1a", 18x"1bba0", 18x"1ba28", 18x"1b8b2", 18x"1b73c", 18x"1b5c6", 18x"1b452",
18x"1b2e0", 18x"1b16e", 18x"1affe", 18x"1ae8e", 18x"1ad20", 18x"1abb4", 18x"1aa46", 18x"1a8dc",
-- 2.0 ... 2.9999
18x"1a772", 18x"1a608", 18x"1a4a0", 18x"1a33a", 18x"1a1d4", 18x"1a070", 18x"19f0c", 18x"19da8",
18x"19c48", 18x"19ae6", 18x"19986", 18x"19828", 18x"196ca", 18x"1956e", 18x"19412", 18x"192b8",
18x"1915e", 18x"19004", 18x"18eae", 18x"18d56", 18x"18c00", 18x"18aac", 18x"18958", 18x"18804",
18x"186b2", 18x"18562", 18x"18412", 18x"182c2", 18x"18174", 18x"18026", 18x"17eda", 18x"17d8e",
18x"17c44", 18x"17afa", 18x"179b2", 18x"1786a", 18x"17724", 18x"175de", 18x"17498", 18x"17354",
18x"17210", 18x"170ce", 18x"16f8c", 18x"16e4c", 18x"16d0c", 18x"16bcc", 18x"16a8e", 18x"16950",
18x"16814", 18x"166d8", 18x"1659e", 18x"16464", 18x"1632a", 18x"161f2", 18x"160ba", 18x"15f84",
18x"15e4e", 18x"15d1a", 18x"15be6", 18x"15ab2", 18x"15980", 18x"1584e", 18x"1571c", 18x"155ec",
18x"154bc", 18x"1538e", 18x"15260", 18x"15134", 18x"15006", 18x"14edc", 18x"14db0", 18x"14c86",
18x"14b5e", 18x"14a36", 18x"1490e", 18x"147e6", 18x"146c0", 18x"1459a", 18x"14476", 18x"14352",
18x"14230", 18x"1410c", 18x"13fea", 18x"13eca", 18x"13daa", 18x"13c8a", 18x"13b6c", 18x"13a4e",
18x"13930", 18x"13814", 18x"136f8", 18x"135dc", 18x"134c2", 18x"133a8", 18x"1328e", 18x"13176",
18x"1305e", 18x"12f48", 18x"12e30", 18x"12d1a", 18x"12c06", 18x"12af2", 18x"129de", 18x"128ca",
18x"127b8", 18x"126a6", 18x"12596", 18x"12486", 18x"12376", 18x"12266", 18x"12158", 18x"1204a",
18x"11f3e", 18x"11e32", 18x"11d26", 18x"11c1a", 18x"11b10", 18x"11a06", 18x"118fc", 18x"117f4",
18x"116ec", 18x"115e4", 18x"114de", 18x"113d8", 18x"112d2", 18x"111ce", 18x"110ca", 18x"10fc6",
18x"10ec2", 18x"10dc0", 18x"10cbe", 18x"10bbc", 18x"10abc", 18x"109bc", 18x"108bc", 18x"107be",
18x"106c0", 18x"105c2", 18x"104c4", 18x"103c8", 18x"102cc", 18x"101d0", 18x"100d6", 18x"0ffdc",
18x"0fee2", 18x"0fdea", 18x"0fcf0", 18x"0fbf8", 18x"0fb02", 18x"0fa0a", 18x"0f914", 18x"0f81e",
18x"0f72a", 18x"0f636", 18x"0f542", 18x"0f44e", 18x"0f35a", 18x"0f268", 18x"0f176", 18x"0f086",
18x"0ef94", 18x"0eea4", 18x"0edb4", 18x"0ecc6", 18x"0ebd6", 18x"0eae8", 18x"0e9fa", 18x"0e90e",
18x"0e822", 18x"0e736", 18x"0e64a", 18x"0e55e", 18x"0e474", 18x"0e38a", 18x"0e2a0", 18x"0e1b8",
18x"0e0d0", 18x"0dfe8", 18x"0df00", 18x"0de1a", 18x"0dd32", 18x"0dc4c", 18x"0db68", 18x"0da82",
18x"0d99e", 18x"0d8ba", 18x"0d7d6", 18x"0d6f4", 18x"0d612", 18x"0d530", 18x"0d44e", 18x"0d36c",
18x"0d28c", 18x"0d1ac", 18x"0d0cc", 18x"0cfee", 18x"0cf0e", 18x"0ce30", 18x"0cd54", 18x"0cc76",
18x"0cb9a", 18x"0cabc", 18x"0c9e0", 18x"0c906", 18x"0c82a", 18x"0c750", 18x"0c676", 18x"0c59c",
18x"0c4c4", 18x"0c3ea", 18x"0c312", 18x"0c23a", 18x"0c164", 18x"0c08c", 18x"0bfb6", 18x"0bee0",
18x"0be0a", 18x"0bd36", 18x"0bc62", 18x"0bb8c", 18x"0baba", 18x"0b9e6", 18x"0b912", 18x"0b840",
18x"0b76e", 18x"0b69c", 18x"0b5cc", 18x"0b4fa", 18x"0b42a", 18x"0b35a", 18x"0b28a", 18x"0b1bc",
18x"0b0ee", 18x"0b01e", 18x"0af50", 18x"0ae84", 18x"0adb6", 18x"0acea", 18x"0ac1e", 18x"0ab52",
18x"0aa86", 18x"0a9bc", 18x"0a8f0", 18x"0a826", 18x"0a75c", 18x"0a694", 18x"0a5ca", 18x"0a502",
18x"0a43a", 18x"0a372", 18x"0a2aa", 18x"0a1e4", 18x"0a11c", 18x"0a056", 18x"09f90", 18x"09ecc",
-- 3.0 ... 3.9999
18x"09e06", 18x"09d42", 18x"09c7e", 18x"09bba", 18x"09af6", 18x"09a32", 18x"09970", 18x"098ae",
18x"097ec", 18x"0972a", 18x"09668", 18x"095a8", 18x"094e8", 18x"09426", 18x"09368", 18x"092a8",
18x"091e8", 18x"0912a", 18x"0906c", 18x"08fae", 18x"08ef0", 18x"08e32", 18x"08d76", 18x"08cba",
18x"08bfe", 18x"08b42", 18x"08a86", 18x"089ca", 18x"08910", 18x"08856", 18x"0879c", 18x"086e2",
18x"08628", 18x"08570", 18x"084b6", 18x"083fe", 18x"08346", 18x"0828e", 18x"081d8", 18x"08120",
18x"0806a", 18x"07fb4", 18x"07efe", 18x"07e48", 18x"07d92", 18x"07cde", 18x"07c2a", 18x"07b76",
18x"07ac2", 18x"07a0e", 18x"0795a", 18x"078a8", 18x"077f4", 18x"07742", 18x"07690", 18x"075de",
18x"0752e", 18x"0747c", 18x"073cc", 18x"0731c", 18x"0726c", 18x"071bc", 18x"0710c", 18x"0705e",
18x"06fae", 18x"06f00", 18x"06e52", 18x"06da4", 18x"06cf6", 18x"06c4a", 18x"06b9c", 18x"06af0",
18x"06a44", 18x"06998", 18x"068ec", 18x"06840", 18x"06796", 18x"066ea", 18x"06640", 18x"06596",
18x"064ec", 18x"06442", 18x"0639a", 18x"062f0", 18x"06248", 18x"061a0", 18x"060f8", 18x"06050",
18x"05fa8", 18x"05f00", 18x"05e5a", 18x"05db4", 18x"05d0e", 18x"05c68", 18x"05bc2", 18x"05b1c",
18x"05a76", 18x"059d2", 18x"0592e", 18x"05888", 18x"057e4", 18x"05742", 18x"0569e", 18x"055fa",
18x"05558", 18x"054b6", 18x"05412", 18x"05370", 18x"052ce", 18x"0522e", 18x"0518c", 18x"050ec",
18x"0504a", 18x"04faa", 18x"04f0a", 18x"04e6a", 18x"04dca", 18x"04d2c", 18x"04c8c", 18x"04bee",
18x"04b50", 18x"04ab0", 18x"04a12", 18x"04976", 18x"048d8", 18x"0483a", 18x"0479e", 18x"04700",
18x"04664", 18x"045c8", 18x"0452c", 18x"04490", 18x"043f6", 18x"0435a", 18x"042c0", 18x"04226",
18x"0418a", 18x"040f0", 18x"04056", 18x"03fbe", 18x"03f24", 18x"03e8c", 18x"03df2", 18x"03d5a",
18x"03cc2", 18x"03c2a", 18x"03b92", 18x"03afa", 18x"03a62", 18x"039cc", 18x"03934", 18x"0389e",
18x"03808", 18x"03772", 18x"036dc", 18x"03646", 18x"035b2", 18x"0351c", 18x"03488", 18x"033f2",
18x"0335e", 18x"032ca", 18x"03236", 18x"031a2", 18x"03110", 18x"0307c", 18x"02fea", 18x"02f56",
18x"02ec4", 18x"02e32", 18x"02da0", 18x"02d0e", 18x"02c7c", 18x"02bec", 18x"02b5a", 18x"02aca",
18x"02a38", 18x"029a8", 18x"02918", 18x"02888", 18x"027f8", 18x"0276a", 18x"026da", 18x"0264a",
18x"025bc", 18x"0252e", 18x"024a0", 18x"02410", 18x"02384", 18x"022f6", 18x"02268", 18x"021da",
18x"0214e", 18x"020c0", 18x"02034", 18x"01fa8", 18x"01f1c", 18x"01e90", 18x"01e04", 18x"01d78",
18x"01cee", 18x"01c62", 18x"01bd8", 18x"01b4c", 18x"01ac2", 18x"01a38", 18x"019ae", 18x"01924",
18x"0189c", 18x"01812", 18x"01788", 18x"01700", 18x"01676", 18x"015ee", 18x"01566", 18x"014de",
18x"01456", 18x"013ce", 18x"01346", 18x"012c0", 18x"01238", 18x"011b2", 18x"0112c", 18x"010a4",
18x"0101e", 18x"00f98", 18x"00f12", 18x"00e8c", 18x"00e08", 18x"00d82", 18x"00cfe", 18x"00c78",
18x"00bf4", 18x"00b70", 18x"00aec", 18x"00a68", 18x"009e4", 18x"00960", 18x"008dc", 18x"00858",
18x"007d6", 18x"00752", 18x"006d0", 18x"0064e", 18x"005cc", 18x"0054a", 18x"004c8", 18x"00446",
18x"003c4", 18x"00342", 18x"002c2", 18x"00240", 18x"001c0", 18x"00140", 18x"000c0", 18x"00040"
); );


-- Left and right shifter with 120 bit input and 64 bit output. -- Left and right shifter with 120 bit input and 64 bit output.
@ -424,9 +530,17 @@ begin


-- synchronous reads from lookup table -- synchronous reads from lookup table
lut_access: process(clk) lut_access: process(clk)
variable addrhi : std_ulogic_vector(1 downto 0);
variable addr : std_ulogic_vector(9 downto 0);
begin begin
if rising_edge(clk) then if rising_edge(clk) then
inverse_est <= '1' & inverse_table(to_integer(unsigned(r.b.mantissa(53 downto 46)))); if r.is_sqrt = '1' then
addrhi := r.b.mantissa(55 downto 54);
else
addrhi := "00";
end if;
addr := addrhi & r.b.mantissa(53 downto 46);
inverse_est <= '1' & inverse_table(to_integer(unsigned(addr)));
end if; end if;
end process; end process;


@ -488,6 +602,8 @@ begin
variable pcmpb_eq : std_ulogic; variable pcmpb_eq : std_ulogic;
variable pcmpb_lt : std_ulogic; variable pcmpb_lt : std_ulogic;
variable pshift : std_ulogic; variable pshift : std_ulogic;
variable renorm_sqrt : std_ulogic;
variable sqrt_exp : signed(EXP_BITS-1 downto 0);
begin begin
v := r; v := r;
illegal := '0'; illegal := '0';
@ -519,6 +635,7 @@ begin
v.round_mode := '0' & r.fpscr(FPSCR_RN+1 downto FPSCR_RN); v.round_mode := '0' & r.fpscr(FPSCR_RN+1 downto FPSCR_RN);
v.is_subtract := '0'; v.is_subtract := '0';
v.is_multiply := '0'; v.is_multiply := '0';
v.is_sqrt := '0';
v.add_bsmall := '0'; v.add_bsmall := '0';
adec := decode_dp(e_in.fra, int_input); adec := decode_dp(e_in.fra, int_input);
bdec := decode_dp(e_in.frb, int_input); bdec := decode_dp(e_in.frb, int_input);
@ -599,6 +716,7 @@ begin
msel_inv <= '0'; msel_inv <= '0';
set_y := '0'; set_y := '0';
pshift := '0'; pshift := '0';
renorm_sqrt := '0';
case r.state is case r.state is
when IDLE => when IDLE =>
if e_in.valid = '1' then if e_in.valid = '1' then
@ -654,6 +772,9 @@ begin
when "11001" => when "11001" =>
v.is_multiply := '1'; v.is_multiply := '1';
v.state := DO_FMUL; v.state := DO_FMUL;
when "11010" =>
v.is_sqrt := '1';
v.state := DO_FRSQRTE;
when others => when others =>
illegal := '1'; illegal := '1';
end case; end case;
@ -1157,6 +1278,48 @@ begin
arith_done := '1'; arith_done := '1';
end case; end case;


when DO_FRSQRTE =>
opsel_a <= AIN_B;
v.result_class := r.b.class;
v.result_sign := r.b.negative;
v.fpscr(FPSCR_FR) := '0';
v.fpscr(FPSCR_FI) := '0';
if r.b.class = NAN and r.b.mantissa(53) = '0' then
v.fpscr(FPSCR_VXSNAN) := '1';
invalid := '1';
end if;
v.shift := to_signed(1, EXP_BITS);
case r.b.class is
when FINITE =>
v.result_exp := r.b.exponent;
if r.b.negative = '1' then
v.fpscr(FPSCR_VXSQRT) := '1';
qnan_result := '1';
arith_done := '1';
elsif r.b.mantissa(54) = '0' then
v.state := RENORM_B;
elsif r.b.exponent(0) = '0' then
v.state := RSQRT_1;
else
v.state := RENORM_B2;
end if;
when NAN =>
-- result is B
arith_done := '1';
when INFINITY =>
if r.b.negative = '1' then
v.fpscr(FPSCR_VXSQRT) := '1';
qnan_result := '1';
else
v.result_class := ZERO;
end if;
arith_done := '1';
when ZERO =>
v.result_class := INFINITY;
zero_divide := '1';
arith_done := '1';
end case;

when RENORM_A => when RENORM_A =>
renormalize := '1'; renormalize := '1';
v.state := RENORM_A2; v.state := RENORM_A2;
@ -1184,11 +1347,16 @@ begin


when RENORM_B => when RENORM_B =>
renormalize := '1'; renormalize := '1';
renorm_sqrt := r.is_sqrt;
v.state := RENORM_B2; v.state := RENORM_B2;


when RENORM_B2 => when RENORM_B2 =>
set_b := '1'; set_b := '1';
v.result_exp := r.result_exp + r.shift; if r.is_sqrt = '0' then
v.result_exp := r.result_exp + r.shift;
else
v.result_exp := new_exp;
end if;
v.state := LOOKUP; v.state := LOOKUP;


when RENORM_C => when RENORM_C =>
@ -1287,8 +1455,10 @@ begin
v.first := '1'; v.first := '1';
if r.insn(4) = '0' then if r.insn(4) = '0' then
v.state := DIV_2; v.state := DIV_2;
else elsif r.insn(2) = '0' then
v.state := FRE_1; v.state := FRE_1;
else
v.state := RSQRT_1;
end if; end if;


when DIV_2 => when DIV_2 =>
@ -1367,6 +1537,14 @@ begin
v.shift := to_signed(1, EXP_BITS); v.shift := to_signed(1, EXP_BITS);
v.state := NORMALIZE; v.state := NORMALIZE;


when RSQRT_1 =>
opsel_r <= RES_MISC;
misc_sel <= "0111";
sqrt_exp := r.b.exponent(EXP_BITS-1) & r.b.exponent(EXP_BITS-1 downto 1);
v.result_exp := - sqrt_exp;
v.shift := to_signed(1, EXP_BITS);
v.state := NORMALIZE;

when INT_SHIFT => when INT_SHIFT =>
opsel_r <= RES_SHIFT; opsel_r <= RES_SHIFT;
set_x := '1'; set_x := '1';
@ -1807,6 +1985,10 @@ begin


if renormalize = '1' then if renormalize = '1' then
clz := count_left_zeroes(r.r); clz := count_left_zeroes(r.r);
if renorm_sqrt = '1' then
-- make denormalized value end up with even exponent
clz(0) := '1';
end if;
v.shift := resize(signed('0' & clz) - 9, EXP_BITS); v.shift := resize(signed('0' & clz) - 9, EXP_BITS);
end if; end if;



48
tests/fpu/fpu.c
Unescape Escape View File

@ -1244,6 +1244,53 @@ int fpu_test_20(void)
return trapit(0, test20); return trapit(0, test20);
} }


struct isqrtvals {
unsigned long val;
unsigned long inv;
} isqrtvals[] = {
{ 0x0000000000000000, 0x7ff0000000000000 },
{ 0x8000000000000000, 0xfff0000000000000 },
{ 0xfff0000000000000, 0x7ff8000000000000 },
{ 0x7ff0000000000000, 0x0000000000000000 },
{ 0xfff123456789abcd, 0xfff923456789abcd },
{ 0x3ff0000000000000, 0x3feff80000000000 },
{ 0x4000000000000000, 0x3fe69dc800000000 },
{ 0x4010000000000000, 0x3fdff80000000000 },
{ 0xbff0000000000000, 0x7ff8000000000000 },
{ 0x4008000000000000, 0x3fe2781800000000 },
{ 0x7fd0000000000000, 0x1ffff80000000000 },
{ 0x0008000000000000, 0x5fe69dc800000000 },
{ 0x0004000000000000, 0x5feff80000000000 },
{ 0x0002000000000000, 0x5ff69dc800000000 },
{ 0x0000000000000002, 0x61769dc800000000 },
{ 0x0000000000000001, 0x617ff80000000000 },
};

int test21(long arg)
{
long i;
unsigned long result;
struct isqrtvals *vp = isqrtvals;

set_fpscr(FPS_RN_NEAR);
for (i = 0; i < sizeof(isqrtvals) / sizeof(isqrtvals[0]); ++i, ++vp) {
asm("lfd 6,0(%0); frsqrte 7,6; stfd 7,0(%1)"
: : "b" (&vp->val), "b" (&result) : "memory");
if (result != vp->inv) {
print_hex(i, 2, " ");
print_hex(result, 16, " ");
return i + 1;
}
}
return 0;
}

int fpu_test_21(void)
{
enable_fp();
return trapit(0, test21);
}

int fail = 0; int fail = 0;


void do_test(int num, int (*test)(void)) void do_test(int num, int (*test)(void))
@ -1289,6 +1336,7 @@ int main(void)
do_test(18, fpu_test_18); do_test(18, fpu_test_18);
do_test(19, fpu_test_19); do_test(19, fpu_test_19);
do_test(20, fpu_test_20); do_test(20, fpu_test_20);
do_test(21, fpu_test_21);


return fail; return fail;
} }

BIN
tests/test_fpu.bin
View File

Binary file not shown.

1
tests/test_fpu.console_out
Unescape Escape View File

@ -18,3 +18,4 @@ test 17:PASS
test 18:PASS test 18:PASS
test 19:PASS test 19:PASS
test 20:PASS test 20:PASS
test 21:PASS

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