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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
c2bef73
Enable gen_vector_reduce in fuzz_simplify
alexreinking Mar 30, 2026
a8442de
Cast c0 / lanes to matching integer type
alexreinking Mar 30, 2026
01fe0d6
Merge branch 'main' into mcourteaux/simplify-bug
alexreinking Mar 30, 2026
b4eeeef
More explicit handling of crashing simplify with safe_simplify wrapper.
mcourteaux Mar 30, 2026
8e25c70
Remove noexcept from IRMatcher::BinOp::make
alexreinking Mar 31, 2026
4f85ddd
Print common placeholder names for Wild<i>
alexreinking Mar 31, 2026
7680287
Print h_{add,min,max,and_or} for vector_reduce operators
alexreinking Mar 31, 2026
e1e02da
In the simplifier, assert that the output type matches the result type.
alexreinking Mar 31, 2026
ae4024a
Fix h_or simplify rules that were only valid for lanes == 1
alexreinking Mar 31, 2026
c5f81fc
Revert "In the simplifier, assert that the output type matches the re…
alexreinking Mar 31, 2026
08bfbd6
Simplify h_and rewrite rules by removing redundant lanes == 1 checks.
alexreinking Apr 6, 2026
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39 changes: 24 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 +145,10 @@ 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) ||
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@abadams abadams Mar 30, 2026

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It looks like the analog to the third h_add rule is missing:

rewrite(h_min(broadcast(x, c0), lanes), broadcast(h_min(x, 1), lanes), c0 % lanes == 0) ||

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)) ||
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@abadams abadams Mar 30, 2026

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I think these two rules need to be guarded with no_overflow_type, because ramps are only strictly decreasing or increasing if there's no overflow.

false) {
return mutate(rewrite.result, info);
}
Expand All @@ -156,8 +161,10 @@ 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) ||
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@abadams abadams Mar 30, 2026 •
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Same missing rule as above

rewrite(h_max(ramp(x, y, arg_lanes), 1), x + max(y * (arg_lanes - 1), 0)) ||
rewrite(h_max(ramp(x, y, arg_lanes), lanes), ramp(x + max(y * (factor - 1), 0), y * factor, lanes)) ||
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@abadams abadams Mar 30, 2026

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Needs to be guarded with no_overflow_type, as above

false) {
return mutate(rewrite.result, info);
}
Expand All @@ -170,15 +177,16 @@ 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 +199,8 @@ 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
59 changes: 56 additions & 3 deletions test/correctness/simplify.cpp
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Expand Up @@ -805,11 +805,64 @@ 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));

{
Expr x = Variable::make(Int(32), "x");
Expr y = Variable::make(Int(32), "y");

// == Symbolic Strides ==

// 1. Min: Scalar Reduction (arg_lanes=4, lanes=1 -> factor=4)
check(VectorReduce::make(VectorReduce::Min, Ramp::make(x, y, 4), 1),
min(y, 0) * 3 + x);

// 2. Min: Vector Reduction (arg_lanes=6, lanes=2 -> factor=3)
check(VectorReduce::make(VectorReduce::Min, Ramp::make(x, y, 6), 2),
Ramp::make(min(y, 0) * 2 + x, y * 3, 2));

// 3. Max: Scalar Reduction (arg_lanes=4, lanes=1 -> factor=4)
check(VectorReduce::make(VectorReduce::Max, Ramp::make(x, y, 4), 1),
max(y, 0) * 3 + x);

// 4. Max: Vector Reduction (arg_lanes=6, lanes=2 -> factor=3)
check(VectorReduce::make(VectorReduce::Max, Ramp::make(x, y, 6), 2),
Ramp::make(max(y, 0) * 2 + x, y * 3, 2));

// == Constant Strides (Positive & Negative) ==

// 5. Min: Positive Stride (arg_lanes=8, lanes=2 -> factor=4, stride=2)
// Block 1: min(x, x+2, x+4, x+6) -> x
// Expected Base: x + min(2 * 3, 0) -> x + 0 -> x
// Expected Stride: 2 * 4 = 8
check(VectorReduce::make(VectorReduce::Min, Ramp::make(x, 2, 8), 2),
Ramp::make(x, 8, 2));

// 6. Max: Positive Stride (arg_lanes=8, lanes=2 -> factor=4, stride=2)
// Block 1: max(x, x+2, x+4, x+6) -> x+6
// Expected Base: x + max(2 * 3, 0) -> x + 6
// Expected Stride: 2 * 4 = 8
check(VectorReduce::make(VectorReduce::Max, Ramp::make(x, 2, 8), 2),
Ramp::make(x + 6, 8, 2));

// 7. Min: Negative Stride (arg_lanes=8, lanes=2 -> factor=4, stride=-2)
// Block 1: min(x, x-2, x-4, x-6) -> x-6
// Expected Base: x + min(-2 * 3, 0) -> x - 6
// Expected Stride: -2 * 4 = -8
check(VectorReduce::make(VectorReduce::Min, Ramp::make(x, -2, 8), 2),
Ramp::make(x + -6, -8, 2));

// 8. Max: Negative Stride (arg_lanes=8, lanes=2 -> factor=4, stride=-2)
// Block 1: max(x, x-2, x-4, x-6) -> x
// Expected Base: x + max(-2 * 3, 0) -> x + 0 -> x
// Expected Stride: -2 * 4 = -8
check(VectorReduce::make(VectorReduce::Max, Ramp::make(x, -2, 8), 2),
Ramp::make(x, -8, 2));
}

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