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proc_rmdead: use explicit pattern set when there are no wildcards 

If width of a case expression was large, explicit patterns could cause
the existing logic to take an extremely long time, or exhaust the
maximum size of the underlying set. For cases where all of the patterns
are fully defined and there are no constants in the case expression,
this change uses a simple set to track which patterns have been seen.
This commit is contained in:
Zachary Snow 2021-07-28 17:34:24 -04:00 committed by Zachary Snow
parent 4fec3a85cd
commit c016f6a423
4 changed files with 386 additions and 2 deletions
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65
passes/proc/proc_rmdead.cc
View File

@ -28,9 +28,62 @@
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
void proc_rmdead(RTLIL::SwitchRule *sw, int &counter, int &full_case_counter)
static bool can_use_fully_defined_pool(RTLIL::SwitchRule *sw)
{
BitPatternPool pool(sw->signal);
if (!GetSize(sw->signal))
return false;
for (const RTLIL::SigBit &bit : sw->signal)
if (bit.wire == NULL)
return false;
for (const RTLIL::CaseRule *cas : sw->cases)
for (const RTLIL::SigSpec &sig : cas->compare)
if (!sig.is_fully_def())
return false;
return true;
}
// This replicates the necessary parts of BitPatternPool's interface, but rather
// than storing remaining patterns, this explicitly stores which fully-defined
// constants have already been matched.
struct FullyDefinedPool
{
FullyDefinedPool(const RTLIL::SigSpec &signal)
: max_patterns{signal.size() >= 32 ? 0ul : 1ul << signal.size()}
{}
bool take(RTLIL::SigSpec sig)
{
if (default_reached || patterns.count(sig))
return false;
patterns.insert(sig);
return true;
}
void take_all()
{
default_reached = true;
}
bool empty()
{
return default_reached ||
(max_patterns && max_patterns == patterns.size());
}
pool<RTLIL::SigSpec> patterns;
bool default_reached = false;
size_t max_patterns;
};
void proc_rmdead(RTLIL::SwitchRule *sw, int &counter, int &full_case_counter);
template <class Pool>
static void proc_rmdead_impl(RTLIL::SwitchRule *sw, int &counter, int &full_case_counter)
{
Pool pool(sw->signal);
for (size_t i = 0; i < sw->cases.size(); i++)
{
@ -68,6 +121,14 @@ void proc_rmdead(RTLIL::SwitchRule *sw, int &counter, int &full_case_counter)
}
}
void proc_rmdead(RTLIL::SwitchRule *sw, int &counter, int &full_case_counter)
{
if (can_use_fully_defined_pool(sw))
proc_rmdead_impl<FullyDefinedPool>(sw, counter, full_case_counter);
else
proc_rmdead_impl<BitPatternPool>(sw, counter, full_case_counter);
}
struct ProcRmdeadPass : public Pass {
ProcRmdeadPass() : Pass("proc_rmdead", "eliminate dead trees in decision trees") { }
void help() override

46
tests/proc/rmdead.v Normal file
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@ -0,0 +1,46 @@
module top (
input wire signed x,
output reg [31:0] y
);
wire signed fail = ~x;
always @*
case (x)
1'b0: y = 0;
1'b1: y = 1;
default: y = fail;
endcase
always @*
case (x)
2'sb00: y = 0;
2'sb00: y = fail;
endcase
always @*
case (x)
2'sb00: y = 0;
default: y = fail;
2'sb01: y = 1;
2'sb10: y = 2;
2'sb11: y = 3;
2'sb00: y = fail;
2'sb01: y = fail;
2'sb10: y = fail;
2'sb11: y = fail;
endcase
always @*
case ({x, x})
2'b00: y = 0;
2'b01: y = 1;
2'b10: y = 2;
2'b11: y = 3;
default: y = fail;
2'b00: y = fail;
2'b01: y = fail;
2'b10: y = fail;
2'b11: y = fail;
endcase
endmodule

4
tests/proc/rmdead.ys Normal file
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@ -0,0 +1,4 @@
read_verilog rmdead.v
proc
opt_clean
select -assert-count 0 w:fail

273
tests/simple/case_large.v Normal file
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@ -0,0 +1,273 @@
module top (
input wire [127:0] x,
output reg [31:0] y
);
localparam A = 32'hDEAD_BEEF;
localparam B = 32'h0BAD_0B01;
localparam C = 32'hC001_D00D;
localparam D = 32'h1234_5678;
always @*
case (x)
{C,A,D,B}: y = 142;
{C,A,D,A}: y = 141;
{D,D,A,A}: y = 241;
{A,C,C,D}: y = 44;
{A,A,A,C}: y = 3;
{A,B,A,C}: y = 19;
{A,D,C,C}: y = 59;
{A,A,C,C}: y = 11;
{D,C,B,B}: y = 230;
{A,A,D,D}: y = 16;
{A,C,A,A}: y = 33;
{A,D,D,D}: y = 64;
{D,B,C,B}: y = 218;
{A,C,B,D}: y = 40;
{C,A,B,B}: y = 134;
{A,C,C,C}: y = 43;
{D,A,D,D}: y = 208;
{A,B,C,A}: y = 25;
{B,A,B,B}: y = 70;
{A,C,B,B}: y = 38;
{C,C,C,B}: y = 170;
{C,D,A,C}: y = 179;
{B,C,D,B}: y = 110;
{A,D,A,C}: y = 51;
{C,C,B,B}: y = 166;
{D,D,D,B}: y = 254;
{C,A,D,C}: y = 143;
{C,D,D,B}: y = 190;
{C,B,A,A}: y = 145;
{C,B,A,C}: y = 147;
{B,C,C,B}: y = 106;
{C,D,C,A}: y = 185;
{C,D,B,D}: y = 184;
{D,D,D,D}: y = 256;
{D,C,C,C}: y = 235;
{D,C,D,B}: y = 238;
{A,B,D,C}: y = 31;
{A,C,A,D}: y = 36;
{C,B,C,B}: y = 154;
{A,B,A,A}: y = 17;
{C,B,B,A}: y = 149;
{B,B,D,C}: y = 95;
{B,D,C,B}: y = 122;
{D,B,A,A}: y = 209;
{B,A,B,A}: y = 69;
{B,A,D,A}: y = 77;
{A,B,B,B}: y = 22;
{C,C,C,C}: y = 171;
{C,A,C,B}: y = 138;
{B,A,D,D}: y = 80;
{C,D,D,C}: y = 191;
{B,A,A,C}: y = 67;
{D,C,D,C}: y = 239;
{C,D,D,D}: y = 192;
{C,D,B,B}: y = 182;
{B,B,A,C}: y = 83;
{D,A,A,D}: y = 196;
{A,C,C,B}: y = 42;
{B,C,A,A}: y = 97;
{A,D,B,A}: y = 53;
{D,D,B,C}: y = 247;
{A,A,C,A}: y = 9;
{D,A,C,B}: y = 202;
{A,C,B,C}: y = 39;
{B,C,B,A}: y = 101;
{B,B,B,C}: y = 87;
{C,B,A,B}: y = 146;
{B,D,A,D}: y = 116;
{A,B,D,D}: y = 32;
{B,A,B,C}: y = 71;
{C,A,A,A}: y = 129;
{B,A,D,C}: y = 79;
{B,A,C,B}: y = 74;
{B,B,D,B}: y = 94;
{B,B,C,C}: y = 91;
{D,C,C,A}: y = 233;
{C,A,B,A}: y = 133;
{D,A,B,A}: y = 197;
{D,B,B,D}: y = 216;
{C,C,A,C}: y = 163;
{D,D,B,A}: y = 245;
{B,A,D,B}: y = 78;
{A,B,C,D}: y = 28;
{C,C,C,D}: y = 172;
{D,C,A,D}: y = 228;
{A,C,D,A}: y = 45;
{B,D,C,C}: y = 123;
{C,B,A,D}: y = 148;
{B,D,B,B}: y = 118;
{A,D,A,B}: y = 50;
{C,B,B,C}: y = 151;
{A,A,A,A}: y = 1;
{A,A,B,B}: y = 6;
{B,B,B,B}: y = 86;
{A,D,A,A}: y = 49;
{A,A,A,B}: y = 2;
{B,D,D,A}: y = 125;
{C,C,D,B}: y = 174;
{D,A,D,B}: y = 206;
{D,D,B,D}: y = 248;
{A,A,A,D}: y = 4;
{B,A,A,B}: y = 66;
{B,C,C,A}: y = 105;
{B,C,C,C}: y = 107;
{D,D,D,C}: y = 255;
{B,C,D,D}: y = 112;
{A,D,B,C}: y = 55;
{C,C,C,A}: y = 169;
{C,D,B,C}: y = 183;
{A,A,B,D}: y = 8;
{D,C,B,A}: y = 229;
{C,B,D,A}: y = 157;
{A,D,D,C}: y = 63;
{D,A,D,A}: y = 205;
{A,A,B,C}: y = 7;
{A,C,A,B}: y = 34;
{C,B,D,C}: y = 159;
{C,C,D,D}: y = 176;
{D,D,D,A}: y = 253;
{A,B,B,D}: y = 24;
{B,B,C,A}: y = 89;
{B,D,C,A}: y = 121;
{A,B,C,C}: y = 27;
{A,A,D,C}: y = 15;
{A,B,B,A}: y = 21;
{A,D,A,D}: y = 52;
{D,D,C,C}: y = 251;
{C,D,A,B}: y = 178;
{A,A,D,B}: y = 14;
{D,B,D,B}: y = 222;
{A,C,C,A}: y = 41;
{D,D,A,C}: y = 243;
{A,C,D,B}: y = 46;
{B,B,B,D}: y = 88;
{D,B,B,B}: y = 214;
{C,C,B,D}: y = 168;
{A,D,D,A}: y = 61;
{D,A,C,C}: y = 203;
{D,C,A,C}: y = 227;
{C,D,C,D}: y = 188;
{D,B,D,D}: y = 224;
{A,C,D,C}: y = 47;
{B,A,B,D}: y = 72;
{A,B,B,C}: y = 23;
{C,C,D,A}: y = 173;
{D,B,C,C}: y = 219;
{D,B,C,A}: y = 217;
{A,D,C,D}: y = 60;
{B,B,D,A}: y = 93;
{A,D,C,A}: y = 57;
{C,C,A,A}: y = 161;
{C,B,B,D}: y = 152;
{B,B,B,A}: y = 85;
{B,D,A,A}: y = 113;
{D,C,D,A}: y = 237;
{B,C,B,C}: y = 103;
{A,B,C,B}: y = 26;
{C,D,A,D}: y = 180;
{A,D,B,D}: y = 56;
{D,C,A,B}: y = 226;
{D,B,B,C}: y = 215;
{D,A,B,C}: y = 199;
{B,D,A,C}: y = 115;
{C,B,C,D}: y = 156;
{B,D,D,B}: y = 126;
{D,D,C,B}: y = 250;
{D,C,C,D}: y = 236;
{B,C,B,D}: y = 104;
{C,B,C,A}: y = 153;
{C,B,B,B}: y = 150;
{C,D,C,B}: y = 186;
{C,D,C,C}: y = 187;
{A,D,B,B}: y = 54;
{D,C,C,B}: y = 234;
{C,B,D,D}: y = 160;
{A,B,A,D}: y = 20;
{C,C,B,A}: y = 165;
{C,D,D,A}: y = 189;
{C,C,D,C}: y = 175;
{D,B,D,C}: y = 223;
{B,C,A,B}: y = 98;
{C,C,A,B}: y = 162;
{B,C,D,A}: y = 109;
{D,A,B,D}: y = 200;
{B,D,C,D}: y = 124;
{D,D,C,A}: y = 249;
{B,A,C,C}: y = 75;
{A,A,C,B}: y = 10;
{C,A,B,D}: y = 136;
{B,B,C,D}: y = 92;
{D,D,C,D}: y = 252;
{B,C,A,D}: y = 100;
{C,A,C,C}: y = 139;
{C,A,C,D}: y = 140;
{D,C,A,A}: y = 225;
{A,D,C,B}: y = 58;
{D,B,C,D}: y = 220;
{D,C,B,D}: y = 232;
{B,A,C,D}: y = 76;
{B,B,D,D}: y = 96;
{D,D,B,B}: y = 246;
{C,D,A,A}: y = 177;
{D,D,A,B}: y = 242;
{A,A,D,A}: y = 13;
{B,B,A,D}: y = 84;
{B,C,D,C}: y = 111;
{D,A,A,B}: y = 194;
{C,A,B,C}: y = 135;
{D,A,A,C}: y = 195;
{B,B,A,B}: y = 82;
{D,C,D,D}: y = 240;
{B,C,C,D}: y = 108;
{D,B,A,C}: y = 211;
{A,C,D,D}: y = 48;
{D,A,A,A}: y = 193;
{C,A,A,B}: y = 130;
{D,B,A,D}: y = 212;
{D,A,B,B}: y = 198;
{A,C,B,A}: y = 37;
{B,D,B,D}: y = 120;
{C,C,B,C}: y = 167;
{D,B,A,B}: y = 210;
{A,B,A,B}: y = 18;
{B,C,B,B}: y = 102;
{B,B,A,A}: y = 81;
{D,D,A,D}: y = 244;
{A,B,D,B}: y = 30;
{A,C,A,C}: y = 35;
{A,A,C,D}: y = 12;
{B,D,B,C}: y = 119;
{B,C,A,C}: y = 99;
{D,A,C,A}: y = 201;
{B,A,A,D}: y = 68;
{C,A,A,D}: y = 132;
{B,A,C,A}: y = 73;
{C,C,A,D}: y = 164;
{B,D,B,A}: y = 117;
{A,D,D,B}: y = 62;
{B,D,D,C}: y = 127;
{A,B,D,A}: y = 29;
{C,D,B,A}: y = 181;
{B,B,C,B}: y = 90;
{B,D,A,B}: y = 114;
{B,D,D,D}: y = 128;
{C,A,C,A}: y = 137;
{A,A,B,A}: y = 5;
{C,A,D,D}: y = 144;
{D,C,B,C}: y = 231;
{D,A,C,D}: y = 204;
{C,A,A,C}: y = 131;
{C,B,D,B}: y = 158;
{B,A,A,A}: y = 65;
{D,A,D,C}: y = 207;
{D,B,B,A}: y = 213;
{D,B,D,A}: y = 221;
{C,B,C,C}: y = 155;
default: y = 0;
endcase
endmodule