[PATCH] D112318: [InstCombine] Extend pattern to replace shuffle's insertelement operand

[Piotr Sobczak via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG03961709edd1: [InstCombine] Extend pattern to replace shuffle's insertelement operand (authored by piotr).

Changed prior to commit:
  https://reviews.llvm.org/D112318?vs=381555&id=384360#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112318/new/

https://reviews.llvm.org/D112318

Files:
  llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
  llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll


Index: llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
===================================================================
--- llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
+++ llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
@@ -696,7 +696,7 @@
 ; CHECK-LABEL: @insert_undemanded_element_unequal_length_op0(
 ; CHECK-NEXT:    [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.200000e+01, i32 3
 ; CHECK-NEXT:    call void @use(<4 x float> [[INS]])
-; CHECK-NEXT:    [[S:%.*]] = shufflevector <4 x float> [[INS]], <4 x float> [[Y:%.*]], <5 x i32> <i32 undef, i32 0, i32 7, i32 1, i32 4>
+; CHECK-NEXT:    [[S:%.*]] = shufflevector <4 x float> [[X]], <4 x float> [[Y:%.*]], <5 x i32> <i32 undef, i32 0, i32 7, i32 1, i32 4>
 ; CHECK-NEXT:    ret <5 x float> [[S]]
 ;
   %ins = insertelement <4 x float> %x, float 42.0, i32 3
@@ -709,7 +709,7 @@
 ; CHECK-LABEL: @insert_undemanded_element_unequal_length_op1(
 ; CHECK-NEXT:    [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.200000e+01, i32 3
 ; CHECK-NEXT:    call void @use(<4 x float> [[INS]])
-; CHECK-NEXT:    [[S:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> [[INS]], <5 x i32> <i32 undef, i32 3, i32 2, i32 1, i32 4>
+; CHECK-NEXT:    [[S:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> [[X]], <5 x i32> <i32 undef, i32 3, i32 2, i32 1, i32 4>
 ; CHECK-NEXT:    ret <5 x float> [[S]]
 ;
   %ins = insertelement <4 x float> %x, float 42.0, i32 3
Index: llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -2268,12 +2268,8 @@
   SmallVector<int, 16> Mask;
   Shuf.getShuffleMask(Mask);
 
-  // The shuffle must not change vector sizes.
-  // TODO: This restriction could be removed if the insert has only one use
-  //       (because the transform would require a new length-changing shuffle).
   int NumElts = Mask.size();
-  if (NumElts != (int)(cast<FixedVectorType>(V0->getType())->getNumElements()))
-    return nullptr;
+  int InpNumElts = cast<FixedVectorType>(V0->getType())->getNumElements();
 
   // This is a specialization of a fold in SimplifyDemandedVectorElts. We may
   // not be able to handle it there if the insertelement has >1 use.
@@ -2290,11 +2286,16 @@
   if (match(V1, m_InsertElt(m_Value(X), m_Value(), m_ConstantInt(IdxC)))) {
     // Offset the index constant by the vector width because we are checking for
     // accesses to the 2nd vector input of the shuffle.
-    IdxC += NumElts;
+    IdxC += InpNumElts;
     // shuf ?, (inselt X, ?, IdxC), Mask --> shuf ?, X, Mask
     if (!is_contained(Mask, (int)IdxC))
       return IC.replaceOperand(Shuf, 1, X);
   }
+  // For the rest of the transform, the shuffle must not change vector sizes.
+  // TODO: This restriction could be removed if the insert has only one use
+  //       (because the transform would require a new length-changing shuffle).
+  if (NumElts != InpNumElts)
+    return nullptr;
 
   // shuffle (insert ?, Scalar, IndexC), V1, Mask --> insert V1, Scalar, IndexC'
   auto isShufflingScalarIntoOp1 = [&](Value *&Scalar, ConstantInt *&IndexC) {


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