[ConstantFolding] Add constant folding for scalable vector interleave intrinsics. #168668

topperc · 2025-11-19T05:56:56Z

We can constant fold interleave of identical splat vectors to a larger splat vector.

llvmbot · 2025-11-19T05:57:23Z

@llvm/pr-subscribers-llvm-analysis

@llvm/pr-subscribers-llvm-transforms

Author: Craig Topper (topperc)

Changes

We can constant fold interleave of identical splat vectors to a larger splat vector.

Full diff: https://github.com/llvm/llvm-project/pull/168668.diff

2 Files Affected:

(modified) llvm/lib/Analysis/ConstantFolding.cpp (+16)
(modified) llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll (+112)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
old mode 100755
new mode 100644
index a13df6c5bf552..e1bbcec306edc
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -4307,6 +4307,22 @@ static Constant *ConstantFoldScalableVectorCall(
       return ConstantVector::getNullValue(SVTy);
     break;
   }
+  case Intrinsic::vector_interleave2:
+  case Intrinsic::vector_interleave3:
+  case Intrinsic::vector_interleave4:
+  case Intrinsic::vector_interleave5:
+  case Intrinsic::vector_interleave6:
+  case Intrinsic::vector_interleave7:
+  case Intrinsic::vector_interleave8: {
+    Constant *SplatVal = Operands[0]->getSplatValue();
+    if (!SplatVal)
+      return nullptr;
+
+    if (!llvm::all_equal(Operands))
+      return nullptr;
+
+    return ConstantVector::getSplat(SVTy->getElementCount(), SplatVal);
+  }
   default:
     break;
   }
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll b/llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll
index 848f0d17ff373..2d8a444141a2b 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll
@@ -51,6 +51,22 @@ define <8 x i32> @fold_vector_interleave2() {
   ret <8 x i32> %1
 }
 
+define <vscale x 8 x i32> @fold_scalable_vector_interleave2() {
+; CHECK-LABEL: define <vscale x 8 x i32> @fold_scalable_vector_interleave2() {
+; CHECK-NEXT:    ret <vscale x 8 x i32> zeroinitializer
+;
+  %1 = call <vscale x 8 x i32> @llvm.vector.interleave2.nxv8i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 8 x i32> %1
+}
+
+define <vscale x 8 x i32> @fold_scalable_vector_interleave2_splat() {
+; CHECK-LABEL: define <vscale x 8 x i32> @fold_scalable_vector_interleave2_splat() {
+; CHECK-NEXT:    ret <vscale x 8 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 8 x i32> @llvm.vector.interleave2.nxv8i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 8 x i32> %1
+}
+
 define <12 x i32> @fold_vector_interleave3() {
 ; CHECK-LABEL: define <12 x i32> @fold_vector_interleave3() {
 ; CHECK-NEXT:    ret <12 x i32> <i32 1, i32 5, i32 9, i32 2, i32 6, i32 10, i32 3, i32 7, i32 11, i32 4, i32 8, i32 12>
@@ -59,6 +75,22 @@ define <12 x i32> @fold_vector_interleave3() {
   ret <12 x i32> %1
 }
 
+define <vscale x 12 x i32> @fold_scalable_vector_interleave3() {
+; CHECK-LABEL: define <vscale x 12 x i32> @fold_scalable_vector_interleave3() {
+; CHECK-NEXT:    ret <vscale x 12 x i32> zeroinitializer
+;
+  %1 = call <vscale x 12 x i32> @llvm.vector.interleave3.nxv8i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 12 x i32> %1
+}
+
+define <vscale x 12 x i32> @fold_scalable_vector_interleave3_splat() {
+; CHECK-LABEL: define <vscale x 12 x i32> @fold_scalable_vector_interleave3_splat() {
+; CHECK-NEXT:    ret <vscale x 12 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 12 x i32> @llvm.vector.interleave3.nxv8i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 12 x i32> %1
+}
+
 define <16 x i32> @fold_vector_interleave4() {
 ; CHECK-LABEL: define <16 x i32> @fold_vector_interleave4() {
 ; CHECK-NEXT:    ret <16 x i32> <i32 1, i32 5, i32 9, i32 13, i32 2, i32 6, i32 10, i32 14, i32 3, i32 7, i32 11, i32 15, i32 4, i32 8, i32 12, i32 16>
@@ -67,6 +99,22 @@ define <16 x i32> @fold_vector_interleave4() {
   ret <16 x i32> %1
 }
 
+define <vscale x 16 x i32> @fold_scalable_vector_interleave4() {
+; CHECK-LABEL: define <vscale x 16 x i32> @fold_scalable_vector_interleave4() {
+; CHECK-NEXT:    ret <vscale x 16 x i32> zeroinitializer
+;
+  %1 = call <vscale x 16 x i32> @llvm.vector.interleave4.nxv16i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 16 x i32> %1
+}
+
+define <vscale x 16 x i32> @fold_scalable_vector_interleave4_splat() {
+; CHECK-LABEL: define <vscale x 16 x i32> @fold_scalable_vector_interleave4_splat() {
+; CHECK-NEXT:    ret <vscale x 16 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 16 x i32> @llvm.vector.interleave4.nxv16i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 16 x i32> %1
+}
+
 define <20 x i32> @fold_vector_interleave5() {
 ; CHECK-LABEL: define <20 x i32> @fold_vector_interleave5() {
 ; CHECK-NEXT:    ret <20 x i32> <i32 1, i32 5, i32 9, i32 13, i32 17, i32 2, i32 6, i32 10, i32 14, i32 18, i32 3, i32 7, i32 11, i32 15, i32 19, i32 4, i32 8, i32 12, i32 16, i32 20>
@@ -75,6 +123,22 @@ define <20 x i32> @fold_vector_interleave5() {
   ret <20 x i32> %1
 }
 
+define <vscale x 20 x i32> @fold_scalable_vector_interleave5() {
+; CHECK-LABEL: define <vscale x 20 x i32> @fold_scalable_vector_interleave5() {
+; CHECK-NEXT:    ret <vscale x 20 x i32> zeroinitializer
+;
+  %1 = call <vscale x 20 x i32> @llvm.vector.interleave5.nxv20i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 20 x i32> %1
+}
+
+define <vscale x 20 x i32> @fold_scalable_vector_interleave5_splat() {
+; CHECK-LABEL: define <vscale x 20 x i32> @fold_scalable_vector_interleave5_splat() {
+; CHECK-NEXT:    ret <vscale x 20 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 20 x i32> @llvm.vector.interleave5.nxv20i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 20 x i32> %1
+}
+
 define <24 x i32> @fold_vector_interleave6() {
 ; CHECK-LABEL: define <24 x i32> @fold_vector_interleave6() {
 ; CHECK-NEXT:    ret <24 x i32> <i32 1, i32 5, i32 9, i32 13, i32 17, i32 21, i32 2, i32 6, i32 10, i32 14, i32 18, i32 22, i32 3, i32 7, i32 11, i32 15, i32 19, i32 23, i32 4, i32 8, i32 12, i32 16, i32 20, i32 24>
@@ -83,6 +147,22 @@ define <24 x i32> @fold_vector_interleave6() {
   ret <24 x i32> %1
 }
 
+define <vscale x 24 x i32> @fold_scalable_vector_interleave6() {
+; CHECK-LABEL: define <vscale x 24 x i32> @fold_scalable_vector_interleave6() {
+; CHECK-NEXT:    ret <vscale x 24 x i32> zeroinitializer
+;
+  %1 = call <vscale x 24 x i32> @llvm.vector.interleave6.nxv24i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 24 x i32> %1
+}
+
+define <vscale x 24 x i32> @fold_scalable_vector_interleave6_splat() {
+; CHECK-LABEL: define <vscale x 24 x i32> @fold_scalable_vector_interleave6_splat() {
+; CHECK-NEXT:    ret <vscale x 24 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 24 x i32> @llvm.vector.interleave6.nxv24i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 24 x i32> %1
+}
+
 define <28 x i32> @fold_vector_interleave7() {
 ; CHECK-LABEL: define <28 x i32> @fold_vector_interleave7() {
 ; CHECK-NEXT:    ret <28 x i32> <i32 1, i32 5, i32 9, i32 13, i32 17, i32 21, i32 25, i32 2, i32 6, i32 10, i32 14, i32 18, i32 22, i32 26, i32 3, i32 7, i32 11, i32 15, i32 19, i32 23, i32 27, i32 4, i32 8, i32 12, i32 16, i32 20, i32 24, i32 28>
@@ -91,6 +171,22 @@ define <28 x i32> @fold_vector_interleave7() {
   ret <28 x i32> %1
 }
 
+define <vscale x 28 x i32> @fold_scalable_vector_interleave7() {
+; CHECK-LABEL: define <vscale x 28 x i32> @fold_scalable_vector_interleave7() {
+; CHECK-NEXT:    ret <vscale x 28 x i32> zeroinitializer
+;
+  %1 = call <vscale x 28 x i32> @llvm.vector.interleave7.nxv28i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 28 x i32> %1
+}
+
+define <vscale x 28 x i32> @fold_scalable_vector_interleave7_splat() {
+; CHECK-LABEL: define <vscale x 28 x i32> @fold_scalable_vector_interleave7_splat() {
+; CHECK-NEXT:    ret <vscale x 28 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 28 x i32> @llvm.vector.interleave7.nxv28i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 28 x i32> %1
+}
+
 define <32 x i32> @fold_vector_interleave8() {
 ; CHECK-LABEL: define <32 x i32> @fold_vector_interleave8() {
 ; CHECK-NEXT:    ret <32 x i32> <i32 1, i32 5, i32 9, i32 13, i32 17, i32 21, i32 25, i32 29, i32 2, i32 6, i32 10, i32 14, i32 18, i32 22, i32 26, i32 30, i32 3, i32 7, i32 11, i32 15, i32 19, i32 23, i32 27, i32 31, i32 4, i32 8, i32 12, i32 16, i32 20, i32 24, i32 28, i32 32>
@@ -99,6 +195,22 @@ define <32 x i32> @fold_vector_interleave8() {
   ret <32 x i32> %1
 }
 
+define <vscale x 32 x i32> @fold_scalable_vector_interleave8() {
+; CHECK-LABEL: define <vscale x 32 x i32> @fold_scalable_vector_interleave8() {
+; CHECK-NEXT:    ret <vscale x 32 x i32> zeroinitializer
+;
+  %1 = call <vscale x 32 x i32> @llvm.vector.interleave8.nxv32i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 32 x i32> %1
+}
+
+define <vscale x 32 x i32> @fold_scalable_vector_interleave8_splat() {
+; CHECK-LABEL: define <vscale x 32 x i32> @fold_scalable_vector_interleave8_splat() {
+; CHECK-NEXT:    ret <vscale x 32 x i32> splat (i32 1)
+;
+  %1 = call <vscale x 32 x i32> @llvm.vector.interleave8.nxv32i32(<vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1), <vscale x 4 x i32> splat (i32 1))
+  ret <vscale x 32 x i32> %1
+}
+
 define {<4 x i32>, <4 x i32>} @fold_vector_deinterleave2() {
 ; CHECK-LABEL: define { <4 x i32>, <4 x i32> } @fold_vector_deinterleave2() {
 ; CHECK-NEXT:    ret { <4 x i32>, <4 x i32> } { <4 x i32> <i32 1, i32 2, i32 3, i32 4>, <4 x i32> <i32 5, i32 6, i32 7, i32 8> }

github-actions · 2025-11-19T06:41:27Z

🐧 Linux x64 Test Results

186403 tests passed
4864 tests skipped

dtcxzyw

LG

preames

LGTM w/additional tests added.

llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll

… intrinsics.

…able-interleave

Pre-commit tests. NFC

741a54c

topperc requested review from mshockwave, nikic, npanchen and preames November 19, 2025 05:56

llvmbot added llvm:instcombine Covers the InstCombine, InstSimplify and AggressiveInstCombine passes llvm:analysis Includes value tracking, cost tables and constant folding llvm:transforms labels Nov 19, 2025

dtcxzyw approved these changes Nov 19, 2025

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preames approved these changes Nov 19, 2025

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llvm/test/Transforms/InstSimplify/ConstProp/vector-calls.ll Show resolved Hide resolved

npanchen approved these changes Nov 19, 2025

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topperc force-pushed the pr/constant-fold-scalable-interleave branch from d49c0db to 44f277a Compare November 19, 2025 17:59

topperc added 2 commits November 19, 2025 11:19

fixup! negative test

3a8ad4b

[ConstantFolding] Add constant folding for scalable vector interleave…

d7c17ce

… intrinsics.

topperc force-pushed the pr/constant-fold-scalable-interleave branch from 44f277a to d7c17ce Compare November 19, 2025 19:26

mshockwave approved these changes Nov 19, 2025

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Merge remote-tracking branch 'origin/main' into pr/constant-fold-scal…

64d43d5

…able-interleave

topperc merged commit 8830525 into llvm:main Nov 19, 2025
8 of 9 checks passed

topperc deleted the pr/constant-fold-scalable-interleave branch November 19, 2025 23:50

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[ConstantFolding] Add constant folding for scalable vector interleave intrinsics. #168668

[ConstantFolding] Add constant folding for scalable vector interleave intrinsics. #168668

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[ConstantFolding] Add constant folding for scalable vector interleave intrinsics. #168668

[ConstantFolding] Add constant folding for scalable vector interleave intrinsics. #168668

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