[Matrix] Propagate shape information through Select insts #141876
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@llvm/pr-subscribers-llvm-transforms Author: Jon Roelofs (jroelofs) ChangesFull diff: https://github.com/llvm/llvm-project/pull/141876.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
index 756a72e6d97bc..6cfe077b602d3 100644
--- a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
@@ -269,6 +269,15 @@ computeShapeInfoForInst(Instruction *I,
return OpShape->second;
}
+ if (isa<SelectInst>(I)) {
+ auto OpShape = ShapeMap.find(I->getOperand(1));
+ if (OpShape != ShapeMap.end())
+ return OpShape->second;
+ OpShape = ShapeMap.find(I->getOperand(2));
+ if (OpShape != ShapeMap.end())
+ return OpShape->second;
+ }
+
if (isUniformShape(I)) {
// Find the first operand that has a known shape and use that.
for (auto &Op : I->operands()) {
@@ -623,7 +632,7 @@ class LowerMatrixIntrinsics {
default:
return false;
}
- return isUniformShape(V) || isa<StoreInst>(V) || isa<LoadInst>(V);
+ return isUniformShape(V) || isa<StoreInst>(V) || isa<LoadInst>(V) || isa<SelectInst>(V);
}
/// Propagate the shape information of instructions to their users.
@@ -710,6 +719,12 @@ class LowerMatrixIntrinsics {
} else if (isa<StoreInst>(V)) {
// Nothing to do. We forward-propagated to this so we would just
// backward propagate to an instruction with an already known shape.
+ } else if (auto *Select = dyn_cast<SelectInst>(V)) {
+ ShapeInfo Shape = ShapeMap[V];
+ if (setShapeInfo(Select->getOperand(1), Shape))
+ pushInstruction(Select, WorkList);
+ if (setShapeInfo(Select->getOperand(2), Shape))
+ pushInstruction(Select, WorkList);
} else if (isUniformShape(V)) {
// Propagate to all operands.
ShapeInfo Shape = ShapeMap[V];
@@ -1068,6 +1083,8 @@ class LowerMatrixIntrinsics {
Changed |= VisitBinaryOperator(BinOp);
if (auto *UnOp = dyn_cast<UnaryOperator>(Inst))
Changed |= VisitUnaryOperator(UnOp);
+ if (auto *Select = dyn_cast<SelectInst>(Inst))
+ Changed |= VisitSelectInst(Select);
if (match(Inst, m_Load(m_Value(Op1))))
Changed |= VisitLoad(cast<LoadInst>(Inst), Op1, Builder);
else if (match(Inst, m_Store(m_Value(Op1), m_Value(Op2))))
@@ -2198,6 +2215,35 @@ class LowerMatrixIntrinsics {
return true;
}
+ /// Lower selects, if shape information is available.
+ bool VisitSelectInst(SelectInst *Inst) {
+ auto I = ShapeMap.find(Inst);
+ if (I == ShapeMap.end())
+ return false;
+
+ Value *Cond = Inst->getOperand(0);
+ Value *OpA = Inst->getOperand(1);
+ Value *OpB = Inst->getOperand(2);
+
+ IRBuilder<> Builder(Inst);
+ ShapeInfo &Shape = I->second;
+
+ MatrixTy Result;
+ MatrixTy A = getMatrix(OpA, Shape, Builder);
+ MatrixTy B = getMatrix(OpB, Shape, Builder);
+
+ for (unsigned I = 0; I < Shape.getNumVectors(); ++I) {
+ auto *Sel = Builder.CreateSelect(Cond, A.getVector(I), B.getVector(I));
+ Result.addVector(Sel);
+ }
+
+ finalizeLowering(Inst,
+ Result.addNumComputeOps(getNumOps(Result.getVectorTy()) *
+ Result.getNumVectors()),
+ Builder);
+ return true;
+ }
+
/// Helper to linearize a matrix expression tree into a string. Currently
/// matrix expressions are linarized by starting at an expression leaf and
/// linearizing bottom up.
diff --git a/llvm/test/Transforms/LowerMatrixIntrinsics/select.ll b/llvm/test/Transforms/LowerMatrixIntrinsics/select.ll
new file mode 100644
index 0000000000000..acfd9228ee17a
--- /dev/null
+++ b/llvm/test/Transforms/LowerMatrixIntrinsics/select.ll
@@ -0,0 +1,26 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes='lower-matrix-intrinsics' -S < %s | FileCheck %s
+
+define void @select_2x2(i1 %cond, ptr %lhs, ptr %rhs, ptr %out) {
+; CHECK-LABEL: @select_2x2(
+; CHECK-NEXT: [[COL_LOAD:%.*]] = load <2 x float>, ptr [[LHS:%.*]], align 16
+; CHECK-NEXT: [[VEC_GEP:%.*]] = getelementptr float, ptr [[LHS]], i64 2
+; CHECK-NEXT: [[COL_LOAD1:%.*]] = load <2 x float>, ptr [[VEC_GEP]], align 8
+; CHECK-NEXT: [[COL_LOAD2:%.*]] = load <2 x float>, ptr [[RHS:%.*]], align 16
+; CHECK-NEXT: [[VEC_GEP3:%.*]] = getelementptr float, ptr [[RHS]], i64 2
+; CHECK-NEXT: [[COL_LOAD4:%.*]] = load <2 x float>, ptr [[VEC_GEP3]], align 8
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], <2 x float> [[COL_LOAD]], <2 x float> [[COL_LOAD2]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[COND]], <2 x float> [[COL_LOAD1]], <2 x float> [[COL_LOAD4]]
+; CHECK-NEXT: store <2 x float> [[TMP1]], ptr [[OUT:%.*]], align 16
+; CHECK-NEXT: [[VEC_GEP5:%.*]] = getelementptr float, ptr [[OUT]], i64 2
+; CHECK-NEXT: store <2 x float> [[TMP2]], ptr [[VEC_GEP5]], align 8
+; CHECK-NEXT: ret void
+;
+ %lhsv = load <4 x float>, ptr %lhs
+ %rhsv = load <4 x float>, ptr %rhs
+ %op = select i1 %cond, <4 x float> %lhsv, <4 x float> %rhsv
+ %opt = call <4 x float> @llvm.matrix.transpose(<4 x float> %op, i32 2, i32 2)
+ %optt = call <4 x float> @llvm.matrix.transpose(<4 x float> %opt, i32 2, i32 2)
+ store <4 x float> %optt, ptr %out
+ ret void
+}
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jroelofs
commented
May 29, 2025
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fhahn
reviewed
Jun 5, 2025
| ; | ||
| %lhsv = load <4 x float>, ptr %lhs | ||
| %rhsv = load <4 x float>, ptr %rhs | ||
| %op = select i1 %cond, <4 x float> %lhsv, <4 x float> %rhsv |
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this should probably also have a test where %cond is a vector.
And possibly one where we have shape info for %cond, to make sure we don't pick it for the result.
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we should pick that operand for the shape info if we have it and it's a vector, right?
Comment on lines
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| auto OpShape = ShapeMap.find(I->getOperand(1)); | ||
| if (OpShape != ShapeMap.end()) | ||
| return OpShape->second; | ||
| OpShape = ShapeMap.find(I->getOperand(2)); | ||
| if (OpShape != ShapeMap.end()) | ||
| return OpShape->second; |
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Picking the first operand with shape info should match what we do for uniform shapes, would probably be good to add a similar comment here (or unify the code below by only iterating over op1 & op2 for selects, via something like drop_front(I->operands()) not sure how much extra code that would be)
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ooh, that's a little nicer
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I think it should almost match, but not quite: we need to ignore the condition operand for shape info iff it is not a vector.
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