[otbn,dv] Add register type coverage for GPR insn fields
This code adds coverpoints and crosses to track the generic coverage
targets we have for GPR fields of instructions.
It also fixes the bits for "off_cp" coverpoints that are used to track
immediate offsets for bn.lid, bn.sid, beq and bne.
Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/hw/ip/otbn/doc/dv/index.md b/hw/ip/otbn/doc/dv/index.md
index f6f4bf7..f7d1803 100644
--- a/hw/ip/otbn/doc/dv/index.md
+++ b/hw/ip/otbn/doc/dv/index.md
@@ -156,6 +156,13 @@
For any instruction that reads from or writes to a GPR, we expect to see that operand equal to `x0`, `x1` and an arbitrary register in the range `x2 .. x31`.
We don't have any particular coverage requirements for WDRs (since all of them work essentially the same).
+> As for immediates, the code to track this is split by encoding-schema in `otbn_env_cov`.
+> Each register field gets a coverpoint with the same name, defined with the `DEF_GPR_CP` helper macro.
+> If the encoding schema has more than one instruction, the coverpoint is then crossed with the mnemonic, using the `DEF_MNEM_CROSS` helper macro.
+> For example, `add` is in the `enc_bnr_cg` covergroup.
+> This encoding schema's `GRD` field is tracked with the `grd_cp` coverpoint.
+> Finally, the relevant cross is called `grd_cross`.
+
For any source GPR, we require "toggle coverage" for its value.
For example, `ADD` reads from its `<grs1>` operand.
We want to see each of the 32 bits of that operand set and unset (giving 64 coverage points).
diff --git a/hw/ip/otbn/dv/uvm/env/otbn_env_cov.sv b/hw/ip/otbn/dv/uvm/env/otbn_env_cov.sv
index 91ce09a..56387c8 100644
--- a/hw/ip/otbn/dv/uvm/env/otbn_env_cov.sv
+++ b/hw/ip/otbn/dv/uvm/env/otbn_env_cov.sv
@@ -75,8 +75,27 @@
// bins mnem_add = {mnem_add};
`define DEF_MNEM_BIN(NAME) bins NAME = {NAME}
- // Cross a coverpoint with mnemonic_cp
-`define DEF_MNEM_CROSS(BASENAME) BASENAME``_cross: cross BASENAME``_cp, mnemonic_cp;
+ // Cross one, two or three coverpoints with mnemonic_cp.
+ //
+ // This is intentended to be used inside covergroups that support multiple instructions. In each
+ // of these, we define a coverpoint called mnemonic_cp to track which instruction is being
+ // sampled.
+`define DEF_MNEM_CROSS(BASENAME) \
+ BASENAME``_cross: cross BASENAME``_cp, mnemonic_cp;
+`define DEF_MNEM_CROSS2(BASE0, BASE1) \
+ BASE0``_``BASE1``_cross: cross BASE0``_cp, BASE1``_cp, mnemonic_cp;
+`define DEF_MNEM_CROSS3(BASE0, BASE1, BASE2) \
+ BASE0``_``BASE1``_``BASE2``_cross: \
+ cross BASE0``_cp, BASE1``_cp, BASE2``_cp, mnemonic_cp;
+
+ // A macro to define bins for GPR types. The point is that there are 3 interesting types of GPR:
+ // x0, x1 and everything else.
+`define GPR_BIN_TYPES \
+ { bins gpr_x0 = {5'd0}; bins gpr_x1 = {5'd1}; bins gpr_other = {[5'd2:$]}; }
+
+ // Declare a GPR coverpoint with the 3 types above
+`define DEF_GPR_CP(NAME, BITS) \
+ NAME: coverpoint insn_data[BITS] `GPR_BIN_TYPES
// Per-encoding covergroups
covergroup enc_bna_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -210,6 +229,10 @@
grd_inc_cp: coverpoint insn_data[7];
grs_inc_cp: coverpoint insn_data[9];
+
+ `DEF_GPR_CP(grs_cp, 19:15)
+ `DEF_GPR_CP(grd_cp, 24:20)
+ `DEF_MNEM_CROSS2(grs, grd)
endgroup
covergroup enc_bnr_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -242,9 +265,16 @@
inc1_cp: coverpoint insn_data[8];
off_cp: coverpoint {insn_data[31:25], insn_data[11:9]} { bins extremes[] = {'0, '1}; }
+ `DEF_GPR_CP(grs1_cp, 19:15)
+ // Note: Bits 24:20 are called grd for BN.LID or grs2 for BN.SID, but both are a GPR, so can be
+ // tracked the same here.
+ `DEF_GPR_CP(grx_cp, 24:20)
+
`DEF_MNEM_CROSS(incd)
`DEF_MNEM_CROSS(inc1)
`DEF_MNEM_CROSS(off)
+
+ `DEF_MNEM_CROSS2(grs1, grx)
endgroup
covergroup enc_b_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -254,8 +284,16 @@
illegal_bins other = default;
}
- off_cp: coverpoint insn_data[31:20] { bins extremes[] = {12'h800, 12'h7ff}; }
+ off_cp: coverpoint {insn_data[31], insn_data[7], insn_data[30:25], insn_data[11:8]} {
+ bins extremes[] = {12'h800, 12'h7ff};
+ }
+
+ `DEF_GPR_CP(grs1_cp, 19:15)
+ `DEF_GPR_CP(grs2_cp, 24:20)
+
`DEF_MNEM_CROSS(off)
+
+ `DEF_MNEM_CROSS2(grs1, grs2)
endgroup
covergroup enc_fixed_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -280,7 +318,13 @@
}
imm_cp: coverpoint insn_data[31:20] { bins extremes[] = {12'h800, 12'h7ff}; }
+
+ `DEF_GPR_CP(grd_cp, 11:7)
+ `DEF_GPR_CP(grs1_cp, 19:15)
+
`DEF_MNEM_CROSS(imm)
+
+ `DEF_MNEM_CROSS2(grd, grs1)
endgroup
covergroup enc_is_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -293,7 +337,13 @@
}
shamt_cp: coverpoint insn_data[24:20] { bins extremes[] = {'0, '1}; }
+
+ `DEF_GPR_CP(grd_cp, 11:7)
+ `DEF_GPR_CP(grs1_cp, 19:15)
+
`DEF_MNEM_CROSS(shamt)
+
+ `DEF_MNEM_CROSS2(grd, grs1)
endgroup
covergroup enc_j_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -303,6 +353,8 @@
}
off_cp: coverpoint insn_data[31:12] { bins extremes[] = {20'h80000, 20'h7ffff}; }
+
+ `DEF_GPR_CP(grd_cp, 11:7)
endgroup
covergroup enc_loop_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -313,6 +365,8 @@
}
sz_cp: coverpoint insn_data[31:20] { bins extremes[] = {'0, '1}; }
+
+ `DEF_GPR_CP(grs_cp, 19:15)
endgroup
covergroup enc_loopi_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -338,6 +392,12 @@
`DEF_MNEM_BIN(mnem_xor);
illegal_bins other = default;
}
+
+ `DEF_GPR_CP(grd_cp, 11:7)
+ `DEF_GPR_CP(grs1_cp, 19:15)
+ `DEF_GPR_CP(grs2_cp, 24:20)
+
+ `DEF_MNEM_CROSS3(grd, grs1, grs2)
endgroup
covergroup enc_s_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -346,7 +406,13 @@
illegal_bins other = default;
}
- off_cp: coverpoint insn_data[31:20] { bins extremes[] = {12'h800, 12'h7ff}; }
+ off_cp: coverpoint {insn_data[31:25], insn_data[11:7]} {
+ bins extremes[] = {12'h800, 12'h7ff};
+ }
+
+ `DEF_GPR_CP(grs1_cp, 19:15)
+ `DEF_GPR_CP(grs2_cp, 24:20)
+ `DEF_MNEM_CROSS2(grs1, grs2)
endgroup
covergroup enc_u_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -356,6 +422,8 @@
}
imm_cp: coverpoint insn_data[31:12] { bins extremes[] = {'0, '1}; }
+
+ `DEF_GPR_CP(grd_cp, 11:7)
endgroup
covergroup enc_wcsr_cg with function sample(mnem_str_t mnemonic, logic [31:0] insn_data);
@@ -512,5 +580,9 @@
`undef DEF_MNEM_BIN
`undef DEF_MNEM_CROSS
+`undef DEF_MNEM_CROSS2
+`undef DEF_MNEM_CROSS3
+`undef GPR_BIN_TYPES
+`undef DEF_GPR_CP
endclass
