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opt_expr: fix const lhs of $pow to $shl

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This commit is contained in:
Emil J. Tywoniak 2026-02-02 19:09:30 +01:00
parent ac427a79b0
commit 3bfeaee8ca
2 changed files with 61 additions and 2 deletions
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7
passes/opt/opt_expr.cc
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@ -1667,7 +1667,11 @@ skip_identity:
int bit_idx; int bit_idx;
const auto onehot = sig_a.is_onehot(&bit_idx); const auto onehot = sig_a.is_onehot(&bit_idx);
if (onehot) { // Power of two
// A is unsigned or positive
if (onehot && (!cell->parameters[ID::A_SIGNED].as_bool() || bit_idx < sig_a.size() - 1)) {
cell->parameters[ID::A_SIGNED] = 0;
// 2^B = 1<<B
if (bit_idx == 1) { if (bit_idx == 1) {
log_debug("Replacing pow cell `%s' in module `%s' with left-shift\n", log_debug("Replacing pow cell `%s' in module `%s' with left-shift\n",
cell->name.c_str(), module->name.c_str()); cell->name.c_str(), module->name.c_str());
@ -1679,7 +1683,6 @@ skip_identity:
log_debug("Replacing pow cell `%s' in module `%s' with multiply and left-shift\n", log_debug("Replacing pow cell `%s' in module `%s' with multiply and left-shift\n",
cell->name.c_str(), module->name.c_str()); cell->name.c_str(), module->name.c_str());
cell->type = ID($mul); cell->type = ID($mul);
cell->parameters[ID::A_SIGNED] = 0;
cell->setPort(ID::A, Const(bit_idx, cell->parameters[ID::A_WIDTH].as_int())); cell->setPort(ID::A, Const(bit_idx, cell->parameters[ID::A_WIDTH].as_int()));
SigSpec y_wire = module->addWire(NEW_ID, y_size); SigSpec y_wire = module->addWire(NEW_ID, y_size);

56
tests/opt/opt_expr.ys
View file

@ -319,3 +319,59 @@ check
equiv_opt -assert opt_expr -keepdc equiv_opt -assert opt_expr -keepdc
design -load postopt design -load postopt
select -assert-count 1 t:$mul r:A_WIDTH=4 %i r:B_WIDTH=4 %i r:Y_WIDTH=8 %i select -assert-count 1 t:$mul r:A_WIDTH=4 %i r:B_WIDTH=4 %i r:Y_WIDTH=8 %i
###########
design -reset
read_rtlil <<EOF
module \top
wire width 3 input 2 \binary
wire width 32 output 3 \y
cell $pow $0
parameter \A_WIDTH 32
parameter \B_WIDTH 3
parameter \A_SIGNED 1
parameter \B_SIGNED 0
parameter \Y_WIDTH 32
connect \A 2
connect \B \binary
connect \Y \y
end
end
EOF
scratchpad -set opt.did_something false
opt_expr
scratchpad -assert opt.did_something true
sat -verify -set binary 0 -prove y 1
sat -verify -set binary 1 -prove y 2
sat -verify -set binary 2 -prove y 4
sat -verify -set binary 3 -prove y 8
###########
design -reset
read_rtlil <<EOF
module \top
wire width 3 input 2 \binary
wire width 32 output 3 \y
cell $pow $0
parameter \A_WIDTH 2
parameter \B_WIDTH 3
parameter \A_SIGNED 1
parameter \B_SIGNED 0
parameter \Y_WIDTH 32
connect \A 2'10
connect \B \binary
connect \Y \y
end
end
EOF
scratchpad -set opt.did_something false
opt_expr
scratchpad -assert opt.did_something false