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core: Add support for floating-point loads and stores

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This extends the register file so it can hold FPR values, and
implements the FP loads and stores that do not require conversion
between single and double precision.

We now have the FP, FE0 and FE1 bits in MSR.  FP loads and stores
cause a FP unavailable interrupt if MSR[FP] = 0.

The FPU facilities are optional and their presence is controlled by
the HAS_FPU generic passed down from the top-level board file.  It
defaults to true for all except the A7-35 boards.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras
2020-08-28 12:49:48 +10:00
parent e1672ea709
commit 45cd8f4fc3
18 changed files with 217 additions and 65 deletions
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30
decode2.vhdl
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@@ -11,6 +11,7 @@ use work.insn_helpers.all;
entity decode2 is
generic (
EX1_BYPASS : boolean := true;
HAS_FPU : boolean := true;
-- Non-zero to enable log data collection
LOG_LENGTH : natural := 0
);
@@ -73,7 +74,7 @@ architecture behaviour of decode2 is
-- If it's all 0, we don't treat it as a dependency as slow SPRs
-- operations are single issue.
--
assert is_fast_spr(ispr) = '1' or ispr = "000000"
assert is_fast_spr(ispr) = '1' or ispr = "0000000"
report "Decode A says SPR but ISPR is invalid:" &
to_hstring(ispr) severity failure;
return (is_fast_spr(ispr), ispr, reg_data);
@@ -118,7 +119,7 @@ architecture behaviour of decode2 is
-- ISPR must be either a valid fast SPR number or all 0 for a slow SPR.
-- If it's all 0, we don't treat it as a dependency as slow SPRs
-- operations are single issue.
assert is_fast_spr(ispr) = '1' or ispr = "000000"
assert is_fast_spr(ispr) = '1' or ispr = "0000000"
report "Decode B says SPR but ISPR is invalid:" &
to_hstring(ispr) severity failure;
ret := (is_fast_spr(ispr), ispr, reg_data);
@@ -137,6 +138,12 @@ architecture behaviour of decode2 is
return ('1', gpr_to_gspr(insn_rs(insn_in)), reg_data);
when RCR =>
return ('1', gpr_to_gspr(insn_rcreg(insn_in)), reg_data);
when FRS =>
if HAS_FPU then
return ('1', fpr_to_gspr(insn_frt(insn_in)), reg_data);
else
return ('0', (others => '0'), (others => '0'));
end if;
when NONE =>
return ('0', (others => '0'), (others => '0'));
end case;
@@ -150,16 +157,22 @@ architecture behaviour of decode2 is
return ('1', gpr_to_gspr(insn_rt(insn_in)));
when RA =>
return ('1', gpr_to_gspr(insn_ra(insn_in)));
when FRT =>
if HAS_FPU then
return ('1', fpr_to_gspr(insn_frt(insn_in)));
else
return ('0', "0000000");
end if;
when SPR =>
-- ISPR must be either a valid fast SPR number or all 0 for a slow SPR.
-- If it's all 0, we don't treat it as a dependency as slow SPRs
-- operations are single issue.
assert is_fast_spr(ispr) = '1' or ispr = "000000"
assert is_fast_spr(ispr) = '1' or ispr = "0000000"
report "Decode B says SPR but ISPR is invalid:" &
to_hstring(ispr) severity failure;
return (is_fast_spr(ispr), ispr);
when NONE =>
return ('0', "000000");
return ('0', "0000000");
end case;
end;
@@ -212,7 +225,7 @@ architecture behaviour of decode2 is
signal gpr_b_bypass : std_ulogic;
signal gpr_c_read_valid : std_ulogic;
signal gpr_c_read : gpr_index_t;
signal gpr_c_read : gspr_index_t;
signal gpr_c_bypass : std_ulogic;
signal cr_write_valid : std_ulogic;
@@ -284,8 +297,9 @@ begin
else gpr_to_gspr(insn_ra(d_in.insn));
r_out.read2_reg <= d_in.ispr2 when d_in.decode.input_reg_b = SPR
else gpr_to_gspr(insn_rb(d_in.insn));
r_out.read3_reg <= insn_rcreg(d_in.insn) when d_in.decode.input_reg_c = RCR
else insn_rs(d_in.insn);
r_out.read3_reg <= gpr_to_gspr(insn_rcreg(d_in.insn)) when d_in.decode.input_reg_c = RCR
else fpr_to_gspr(insn_frt(d_in.insn)) when d_in.decode.input_reg_c = FRS and HAS_FPU
else gpr_to_gspr(insn_rs(d_in.insn));
c_out.read <= d_in.decode.input_cr;
@@ -394,7 +408,7 @@ begin
gpr_b_read <= decoded_reg_b.reg;
gpr_c_read_valid <= decoded_reg_c.reg_valid;
gpr_c_read <= gspr_to_gpr(decoded_reg_c.reg);
gpr_c_read <= decoded_reg_c.reg;
cr_write_valid <= d_in.decode.output_cr or decode_rc(d_in.decode.rc, d_in.insn);
cr_bypass_avail <= '0';