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fix(simplifier): VectorReduce(Broadcast(Vector)) used wrong semantics of Broadcast(Vector). #9074

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fix(simplifier): VectorReduce(Broadcast(Vector)) used wrong semantics of Broadcast(Vector). #9074

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2f810de
fix(simplifier): VectorReduce(Broadcast(Vector)) used wrong semantics…
mcourteaux Mar 22, 2026
88900c9
Merge branch 'main' into mcourteaux/simplify-bug
mcourteaux Mar 22, 2026
0526414
improve(simplifier): More general rules for VectorReduce max/min of R…
mcourteaux Mar 23, 2026
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37 changes: 22 additions & 15 deletions src/Simplify_Exprs.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -130,7 +130,10 @@ Expr Simplify::visit(const VectorReduce *op, ExprInfo *info) {
auto rewrite = IRMatcher::rewriter(IRMatcher::h_add(value, lanes), op->type);
if (rewrite(h_add(x * broadcast(y, arg_lanes), lanes), h_add(x, lanes) * broadcast(y, lanes)) ||
rewrite(h_add(broadcast(x, arg_lanes) * y, lanes), h_add(y, lanes) * broadcast(x, lanes)) ||
rewrite(h_add(broadcast(x, arg_lanes), lanes), broadcast(x * factor, lanes))) {
rewrite(h_add(broadcast(x, arg_lanes), lanes), broadcast(x * factor, lanes)) ||
rewrite(h_add(broadcast(x, c0), lanes), broadcast(h_add(x, lanes / c0), c0), lanes % c0 == 0) ||
rewrite(h_add(broadcast(x, c0), lanes), broadcast(h_add(x, 1) * (c0 / lanes), lanes), c0 % lanes == 0) ||
false) {
return mutate(rewrite.result, info);
}
break;
Expand All @@ -142,8 +145,9 @@ Expr Simplify::visit(const VectorReduce *op, ExprInfo *info) {
rewrite(h_min(max(x, broadcast(y, arg_lanes)), lanes), max(h_min(x, lanes), broadcast(y, lanes))) ||
rewrite(h_min(max(broadcast(x, arg_lanes), y), lanes), max(h_min(y, lanes), broadcast(x, lanes))) ||
rewrite(h_min(broadcast(x, arg_lanes), lanes), broadcast(x, lanes)) ||
rewrite(h_min(broadcast(x, c0), lanes), h_min(x, lanes), factor % c0 == 0) ||
rewrite(h_min(ramp(x, y, arg_lanes), lanes), x + min(y * (arg_lanes - 1), 0)) ||
rewrite(h_min(broadcast(x, c0), 1), h_min(x, 1)) ||
rewrite(h_min(broadcast(x, c0), lanes), broadcast(h_min(x, lanes / c0), c0), lanes % c0 == 0) ||
(lanes == 1 && rewrite(h_min(ramp(x, y, arg_lanes), lanes), x + min(y * (arg_lanes - 1), 0))) ||
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@abadams abadams Mar 23, 2026

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I think this (and the max one) could be more general:

rewrite(h_min(ramp(x, y, arg_lanes), 1), x + min(y * (arg_lanes - 1), 0)) ||
rewrite(h_min(ramp(x, y, arg_lanes), lanes), ramp(x + min(y * (factor - 1), 0), y * factor, lanes)) ||

Not sure if the more general case would ever come up though. Maybe it's not worth it.

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@mcourteaux mcourteaux Mar 23, 2026

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With some assistance of Claude to break it down, I am convinced too that these more general rules are good. I'll add them, along with some tests.

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@mcourteaux mcourteaux Mar 23, 2026 •
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Added them! Code formatting looks a lot better. 🥳

false) {
return mutate(rewrite.result, info);
}
Expand All @@ -156,8 +160,9 @@ Expr Simplify::visit(const VectorReduce *op, ExprInfo *info) {
rewrite(h_max(max(x, broadcast(y, arg_lanes)), lanes), max(h_max(x, lanes), broadcast(y, lanes))) ||
rewrite(h_max(max(broadcast(x, arg_lanes), y), lanes), max(h_max(y, lanes), broadcast(x, lanes))) ||
rewrite(h_max(broadcast(x, arg_lanes), lanes), broadcast(x, lanes)) ||
rewrite(h_max(broadcast(x, c0), lanes), h_max(x, lanes), factor % c0 == 0) ||
rewrite(h_max(ramp(x, y, arg_lanes), lanes), x + max(y * (arg_lanes - 1), 0)) ||
rewrite(h_max(broadcast(x, c0), 1), h_max(x, 1)) ||
rewrite(h_max(broadcast(x, c0), lanes), broadcast(h_max(x, lanes / c0), c0), lanes % c0 == 0) ||
(lanes == 1 && rewrite(h_max(ramp(x, y, arg_lanes), lanes), x + max(y * (arg_lanes - 1), 0))) ||
false) {
return mutate(rewrite.result, info);
}
Expand All @@ -170,15 +175,16 @@ Expr Simplify::visit(const VectorReduce *op, ExprInfo *info) {
rewrite(h_and(x && broadcast(y, arg_lanes), lanes), h_and(x, lanes) && broadcast(y, lanes)) ||
rewrite(h_and(broadcast(x, arg_lanes) && y, lanes), h_and(y, lanes) && broadcast(x, lanes)) ||
rewrite(h_and(broadcast(x, arg_lanes), lanes), broadcast(x, lanes)) ||
rewrite(h_and(broadcast(x, c0), lanes), h_and(x, lanes), factor % c0 == 0) ||
rewrite(h_and(ramp(x, y, arg_lanes) < broadcast(z, arg_lanes), lanes),
x + max(y * (arg_lanes - 1), 0) < z) ||
rewrite(h_and(ramp(x, y, arg_lanes) <= broadcast(z, arg_lanes), lanes),
x + max(y * (arg_lanes - 1), 0) <= z) ||
rewrite(h_and(broadcast(x, arg_lanes) < ramp(y, z, arg_lanes), lanes),
x < y + min(z * (arg_lanes - 1), 0)) ||
rewrite(h_and(broadcast(x, arg_lanes) < ramp(y, z, arg_lanes), lanes),
x <= y + min(z * (arg_lanes - 1), 0)) ||
rewrite(h_and(broadcast(x, c0), lanes), broadcast(h_and(x, lanes / c0), c0), lanes % c0 == 0) ||
rewrite(h_and(broadcast(x, c0), lanes), broadcast(h_and(x, 1), lanes), c0 >= lanes) ||
(lanes == 1 && rewrite(h_and(ramp(x, y, arg_lanes) < broadcast(z, arg_lanes), lanes),
x + max(y * (arg_lanes - 1), 0) < z)) ||
(lanes == 1 && rewrite(h_and(ramp(x, y, arg_lanes) <= broadcast(z, arg_lanes), lanes),
x + max(y * (arg_lanes - 1), 0) <= z)) ||
(lanes == 1 && rewrite(h_and(broadcast(x, arg_lanes) < ramp(y, z, arg_lanes), lanes),
x < y + min(z * (arg_lanes - 1), 0))) ||
(lanes == 1 && rewrite(h_and(broadcast(x, arg_lanes) < ramp(y, z, arg_lanes), lanes),
x <= y + min(z * (arg_lanes - 1), 0))) ||
false) {
return mutate(rewrite.result, info);
}
Expand All @@ -191,7 +197,8 @@ Expr Simplify::visit(const VectorReduce *op, ExprInfo *info) {
rewrite(h_or(x && broadcast(y, arg_lanes), lanes), h_or(x, lanes) && broadcast(y, lanes)) ||
rewrite(h_or(broadcast(x, arg_lanes) && y, lanes), h_or(y, lanes) && broadcast(x, lanes)) ||
rewrite(h_or(broadcast(x, arg_lanes), lanes), broadcast(x, lanes)) ||
rewrite(h_or(broadcast(x, c0), lanes), h_or(x, lanes), factor % c0 == 0) ||
rewrite(h_or(broadcast(x, c0), lanes), broadcast(h_or(x, lanes / c0), c0), lanes % c0 == 0) ||
rewrite(h_or(broadcast(x, c0), lanes), broadcast(h_or(x, 1), lanes), c0 >= lanes) ||
// type of arg_lanes is somewhat indeterminate
rewrite(h_or(ramp(x, y, arg_lanes) < broadcast(z, arg_lanes), lanes),
x + min(y * (arg_lanes - 1), 0) < z) ||
Expand Down
6 changes: 3 additions & 3 deletions test/correctness/simplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -805,11 +805,11 @@ void check_vectors() {
check(VectorReduce::make(VectorReduce::And, Broadcast::make(bool_vector, 4), 1),
VectorReduce::make(VectorReduce::And, bool_vector, 1));
check(VectorReduce::make(VectorReduce::Or, Broadcast::make(bool_vector, 4), 2),
VectorReduce::make(VectorReduce::Or, bool_vector, 2));
Broadcast::make(VectorReduce::make(VectorReduce::Or, bool_vector, 1), 2));
check(VectorReduce::make(VectorReduce::Min, Broadcast::make(int_vector, 4), 4),
int_vector);
Broadcast::make(VectorReduce::make(VectorReduce::Min, int_vector, 1), 4));
check(VectorReduce::make(VectorReduce::Max, Broadcast::make(int_vector, 4), 8),
VectorReduce::make(VectorReduce::Max, Broadcast::make(int_vector, 4), 8));
Broadcast::make(VectorReduce::make(VectorReduce::Max, int_vector, 2), 4));

{
// h_add(broadcast(x, 8), 4) should simplify to broadcast(x * 2, 4)
Expand Down
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