[llvm] 6080387 - [InstSimplify] fold splat of inserted constant to vector constant
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Sun Dec 15 06:33:40 PST 2019
Author: Sanjay Patel
Date: 2019-12-15T09:32:03-05:00
New Revision: 6080387f136af5a51bbc310abb08c7158d7cd9d2
URL: https://github.com/llvm/llvm-project/commit/6080387f136af5a51bbc310abb08c7158d7cd9d2
DIFF: https://github.com/llvm/llvm-project/commit/6080387f136af5a51bbc310abb08c7158d7cd9d2.diff
LOG: [InstSimplify] fold splat of inserted constant to vector constant
shuf (inselt ?, C, IndexC), undef, <IndexC, IndexC...> --> <C, C...>
This is another missing shuffle fold pattern uncovered by the
shuffle correctness fix from D70246.
The problem was visible in the post-commit thread example, but
we managed to overcome the limitation for that particular case
with D71220.
This is something like the inverse of the previous fix - there
we didn't demand the inserted scalar, and here we are only
demanding an inserted scalar.
Differential Revision: https://reviews.llvm.org/D71488
Added:
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
llvm/test/Transforms/InstSimplify/shufflevector.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index fd67078940bd..afcca2ab1fa3 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4452,6 +4452,30 @@ static Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
ShuffleVectorInst::commuteShuffleMask(Indices, InVecNumElts);
}
+ // A splat of an inserted scalar constant becomes a vector constant:
+ // shuf (inselt ?, C, IndexC), undef, <IndexC, IndexC...> --> <C, C...>
+ // NOTE: We may have commuted above, so analyze the updated Indices, not the
+ // original mask constant.
+ Constant *C;
+ ConstantInt *IndexC;
+ if (match(Op0, m_InsertElement(m_Value(), m_Constant(C),
+ m_ConstantInt(IndexC)))) {
+ // Match a splat shuffle mask of the insert index allowing undef elements.
+ int InsertIndex = IndexC->getZExtValue();
+ if (all_of(Indices, [InsertIndex](int MaskElt) {
+ return MaskElt == InsertIndex || MaskElt == -1;
+ })) {
+ assert(isa<UndefValue>(Op1) && "Expected undef operand 1 for splat");
+
+ // Shuffle mask undefs become undefined constant result elements.
+ SmallVector<Constant *, 16> VecC(MaskNumElts, C);
+ for (unsigned i = 0; i != MaskNumElts; ++i)
+ if (Indices[i] == -1)
+ VecC[i] = UndefValue::get(C->getType());
+ return ConstantVector::get(VecC);
+ }
+ }
+
// A shuffle of a splat is always the splat itself. Legal if the shuffle's
// value type is same as the input vectors' type.
if (auto *OpShuf = dyn_cast<ShuffleVectorInst>(Op0))
diff --git a/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll b/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
index 83fd7b6129ee..d29bcc7d4172 100644
--- a/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
@@ -725,8 +725,7 @@ define <4 x float> @insert_demanded_element_op1(<4 x float> %x, <4 x float> %y)
define <4 x float> @splat_constant(<4 x float> %x) {
; CHECK-LABEL: @splat_constant(
; CHECK-NEXT: [[INS3:%.*]] = insertelement <4 x float> [[X:%.*]], float 3.000000e+00, i32 3
-; CHECK-NEXT: [[SPLAT3:%.*]] = shufflevector <4 x float> [[INS3]], <4 x float> undef, <4 x i32> <i32 3, i32 3, i32 3, i32 3>
-; CHECK-NEXT: [[R:%.*]] = fadd <4 x float> [[INS3]], [[SPLAT3]]
+; CHECK-NEXT: [[R:%.*]] = fadd <4 x float> [[INS3]], <float 3.000000e+00, float 3.000000e+00, float 3.000000e+00, float 3.000000e+00>
; CHECK-NEXT: ret <4 x float> [[R]]
;
%ins3 = insertelement <4 x float> %x, float 3.0, i32 3
diff --git a/llvm/test/Transforms/InstSimplify/shufflevector.ll b/llvm/test/Transforms/InstSimplify/shufflevector.ll
index 38d605faee57..14c4205f444b 100644
--- a/llvm/test/Transforms/InstSimplify/shufflevector.ll
+++ b/llvm/test/Transforms/InstSimplify/shufflevector.ll
@@ -250,9 +250,7 @@ define <2 x float> @PR32872(<2 x float> %x) {
define <5 x i8> @splat_inserted_constant(<4 x i8> %x) {
; CHECK-LABEL: @splat_inserted_constant(
-; CHECK-NEXT: [[INS3:%.*]] = insertelement <4 x i8> [[X:%.*]], i8 42, i64 3
-; CHECK-NEXT: [[SPLAT5:%.*]] = shufflevector <4 x i8> [[INS3]], <4 x i8> undef, <5 x i32> <i32 3, i32 3, i32 3, i32 3, i32 3>
-; CHECK-NEXT: ret <5 x i8> [[SPLAT5]]
+; CHECK-NEXT: ret <5 x i8> <i8 42, i8 42, i8 42, i8 42, i8 42>
;
%ins3 = insertelement <4 x i8> %x, i8 42, i64 3
%splat5 = shufflevector <4 x i8> %ins3, <4 x i8> undef, <5 x i32> <i32 3, i32 3, i32 3, i32 3, i32 3>
@@ -261,9 +259,7 @@ define <5 x i8> @splat_inserted_constant(<4 x i8> %x) {
define <4 x float> @splat_inserted_constant_undef_elt(<4 x float> %x) {
; CHECK-LABEL: @splat_inserted_constant_undef_elt(
-; CHECK-NEXT: [[INS1:%.*]] = insertelement <4 x float> [[X:%.*]], float 1.200000e+01, i32 1
-; CHECK-NEXT: [[SPLAT1:%.*]] = shufflevector <4 x float> [[INS1]], <4 x float> undef, <4 x i32> <i32 1, i32 1, i32 undef, i32 1>
-; CHECK-NEXT: ret <4 x float> [[SPLAT1]]
+; CHECK-NEXT: ret <4 x float> <float 1.200000e+01, float 1.200000e+01, float undef, float 1.200000e+01>
;
%ins1 = insertelement <4 x float> %x, float 12.0, i32 1
%splat1 = shufflevector <4 x float> %ins1, <4 x float> undef, <4 x i32> <i32 1, i32 1, i32 undef, i32 1>
@@ -272,9 +268,7 @@ define <4 x float> @splat_inserted_constant_undef_elt(<4 x float> %x) {
define <2 x i8> @splat_inserted_constant_not_canonical(<3 x i8> %x, <3 x i8> %y) {
; CHECK-LABEL: @splat_inserted_constant_not_canonical(
-; CHECK-NEXT: [[INS2:%.*]] = insertelement <3 x i8> [[X:%.*]], i8 23, i7 2
-; CHECK-NEXT: [[SPLAT2:%.*]] = shufflevector <3 x i8> [[Y:%.*]], <3 x i8> [[INS2]], <2 x i32> <i32 undef, i32 5>
-; CHECK-NEXT: ret <2 x i8> [[SPLAT2]]
+; CHECK-NEXT: ret <2 x i8> <i8 undef, i8 23>
;
%ins2 = insertelement <3 x i8> %x, i8 23, i7 2
%splat2 = shufflevector <3 x i8> %y, <3 x i8> %ins2, <2 x i32> <i32 undef, i32 5>
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