[llvm] r365342 - [InstCombine] canonicalize insert+splat to/from element 0 of vector
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 8 09:26:48 PDT 2019
Author: spatel
Date: Mon Jul 8 09:26:48 2019
New Revision: 365342
URL: http://llvm.org/viewvc/llvm-project?rev=365342&view=rev
Log:
[InstCombine] canonicalize insert+splat to/from element 0 of vector
We recognize a splat from element 0 in (VectorUtils) llvm::getSplatValue()
and also in ShuffleVectorInst::isZeroEltSplatMask(), so this converts
to that form for better matching.
The backend generically turns these patterns into build_vector,
so there should be no codegen difference.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp?rev=365342&r1=365341&r2=365342&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp Mon Jul 8 09:26:48 2019
@@ -1346,6 +1346,41 @@ static Instruction *foldSelectShuffleWit
return NewBO;
}
+/// If we have an insert of a scalar to a non-zero element of an undefined
+/// vector and then shuffle that value, that's the same as inserting to the zero
+/// element and shuffling. Splatting from the zero element is recognized as the
+/// canonical form of splat.
+static Instruction *canonicalizeInsertSplat(ShuffleVectorInst &Shuf,
+ InstCombiner::BuilderTy &Builder) {
+ Value *Op0 = Shuf.getOperand(0), *Op1 = Shuf.getOperand(1);
+ Constant *Mask = Shuf.getMask();
+ Value *X;
+ uint64_t IndexC;
+
+ // Match a shuffle that is a splat to a non-zero element.
+ if (!match(Op0, m_OneUse(m_InsertElement(m_Undef(), m_Value(X),
+ m_ConstantInt(IndexC)))) ||
+ !match(Op1, m_Undef()) || match(Mask, m_ZeroInt()) || IndexC == 0)
+ return nullptr;
+
+ // Insert into element 0 of an undef vector.
+ UndefValue *UndefVec = UndefValue::get(Shuf.getType());
+ Constant *Zero = Builder.getInt32(0);
+ Value *NewIns = Builder.CreateInsertElement(UndefVec, X, Zero);
+
+ // Splat from element 0. Any mask element that is undefined remains undefined.
+ // For example:
+ // shuf (inselt undef, X, 2), undef, <2,2,undef>
+ // --> shuf (inselt undef, X, 0), undef, <0,0,undef>
+ unsigned NumMaskElts = Shuf.getType()->getVectorNumElements();
+ SmallVector<Constant *, 16> NewMask(NumMaskElts, Zero);
+ for (unsigned i = 0; i != NumMaskElts; ++i)
+ if (isa<UndefValue>(Mask->getAggregateElement(i)))
+ NewMask[i] = Mask->getAggregateElement(i);
+
+ return new ShuffleVectorInst(NewIns, UndefVec, ConstantVector::get(NewMask));
+}
+
/// Try to fold shuffles that are the equivalent of a vector select.
static Instruction *foldSelectShuffle(ShuffleVectorInst &Shuf,
InstCombiner::BuilderTy &Builder,
@@ -1714,6 +1749,9 @@ Instruction *InstCombiner::visitShuffleV
return &SVI;
}
+ if (Instruction *I = canonicalizeInsertSplat(SVI, Builder))
+ return I;
+
if (Instruction *I = foldSelectShuffle(SVI, Builder, DL))
return I;
Modified: llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll?rev=365342&r1=365341&r2=365342&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll Mon Jul 8 09:26:48 2019
@@ -427,8 +427,8 @@ define <5 x float> @insert_not_undef_shu
define <4 x float> @insert_nonzero_index_splat(float %x) {
; CHECK-LABEL: @insert_nonzero_index_splat(
-; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 2
-; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 2, i32 undef>
+; CHECK-NEXT: [[TMP1:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[TMP1]], <4 x float> undef, <4 x i32> <i32 undef, i32 0, i32 0, i32 undef>
; CHECK-NEXT: ret <4 x float> [[SPLAT]]
;
%xv = insertelement <4 x float> undef, float %x, i32 2
@@ -438,8 +438,8 @@ define <4 x float> @insert_nonzero_index
define <3 x double> @insert_nonzero_index_splat_narrow(double %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_narrow(
-; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x double> undef, double [[X:%.*]], i32 3
-; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x double> [[XV]], <4 x double> undef, <3 x i32> <i32 3, i32 undef, i32 3>
+; CHECK-NEXT: [[TMP1:%.*]] = insertelement <3 x double> undef, double [[X:%.*]], i32 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <3 x double> [[TMP1]], <3 x double> undef, <3 x i32> <i32 0, i32 undef, i32 0>
; CHECK-NEXT: ret <3 x double> [[SPLAT]]
;
%xv = insertelement <4 x double> undef, double %x, i32 3
@@ -449,8 +449,8 @@ define <3 x double> @insert_nonzero_inde
define <5 x i7> @insert_nonzero_index_splat_widen(i7 %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_widen(
-; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x i7> undef, i7 [[X:%.*]], i32 1
-; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x i7> [[XV]], <4 x i7> undef, <5 x i32> <i32 undef, i32 1, i32 1, i32 undef, i32 1>
+; CHECK-NEXT: [[TMP1:%.*]] = insertelement <5 x i7> undef, i7 [[X:%.*]], i32 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <5 x i7> [[TMP1]], <5 x i7> undef, <5 x i32> <i32 undef, i32 0, i32 0, i32 undef, i32 0>
; CHECK-NEXT: ret <5 x i7> [[SPLAT]]
;
%xv = insertelement <4 x i7> undef, i7 %x, i32 1
@@ -458,6 +458,8 @@ define <5 x i7> @insert_nonzero_index_sp
ret <5 x i7> %splat
}
+; Negative test - don't increase instruction count
+
define <4 x float> @insert_nonzero_index_splat_extra_use(float %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_extra_use(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 2
@@ -470,3 +472,29 @@ define <4 x float> @insert_nonzero_index
%splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 2, i32 undef>
ret <4 x float> %splat
}
+
+; Negative test - non-undef base vector
+
+define <4 x float> @insert_nonzero_index_splat_wrong_base(float %x, <4 x float> %y) {
+; CHECK-LABEL: @insert_nonzero_index_splat_wrong_base(
+; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> [[Y:%.*]], float [[X:%.*]], i32 2
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 3, i32 undef>
+; CHECK-NEXT: ret <4 x float> [[SPLAT]]
+;
+ %xv = insertelement <4 x float> %y, float %x, i32 2
+ %splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 3, i32 undef>
+ ret <4 x float> %splat
+}
+
+; Negative test - non-constant insert index
+
+define <4 x float> @insert_nonzero_index_splat_wrong_index(float %x, i32 %index) {
+; CHECK-LABEL: @insert_nonzero_index_splat_wrong_index(
+; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 [[INDEX:%.*]]
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 1, i32 1, i32 undef>
+; CHECK-NEXT: ret <4 x float> [[SPLAT]]
+;
+ %xv = insertelement <4 x float> undef, float %x, i32 %index
+ %splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 1, i32 1, i32 undef>
+ ret <4 x float> %splat
+}
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