[llvm] r341708 - [InstCombine] narrow vector select with padded condition and extracted result (PR38691)
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Fri Sep 7 14:03:34 PDT 2018
Author: spatel
Date: Fri Sep 7 14:03:34 2018
New Revision: 341708
URL: http://llvm.org/viewvc/llvm-project?rev=341708&view=rev
Log:
[InstCombine] narrow vector select with padded condition and extracted result (PR38691)
shuf (sel (shuf NarrowCond, undef, WideMask), X, Y), undef, NarrowMask) -->
sel NarrowCond, (shuf X, undef, NarrowMask), (shuf Y, undef, NarrowMask)
The motivating case from:
https://bugs.llvm.org/show_bug.cgi?id=38691
...is the last regression test. In that case, we're just left with the narrow select.
Note that if we do create new shuffles, they use the existing extraction identity mask,
so there's no danger that this transform creates arbitrary shuffles.
Differential Revision: https://reviews.llvm.org/D51496
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
llvm/trunk/test/Transforms/InstCombine/shuffle-select-narrow.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp?rev=341708&r1=341707&r2=341708&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp Fri Sep 7 14:03:34 2018
@@ -1350,6 +1350,41 @@ static Instruction *foldSelectShuffle(Sh
return NewBO;
}
+/// Match a shuffle-select-shuffle pattern where the shuffles are widening and
+/// narrowing (concatenating with undef and extracting back to the original
+/// length). This allows replacing the wide select with a narrow select.
+Instruction *narrowVectorSelect(ShuffleVectorInst &Shuf,
+ InstCombiner::BuilderTy &Builder) {
+ // This must be a narrowing identity shuffle. It extracts the 1st N elements
+ // of the 1st vector operand of a shuffle.
+ if (!match(Shuf.getOperand(1), m_Undef()) || !Shuf.isIdentityWithExtract())
+ return nullptr;
+
+ // The vector being shuffled must be a vector select that we can eliminate.
+ // TODO: The one-use requirement could be eased if X and/or Y are constants.
+ Value *Cond, *X, *Y;
+ if (!match(Shuf.getOperand(0),
+ m_OneUse(m_Select(m_Value(Cond), m_Value(X), m_Value(Y)))))
+ return nullptr;
+
+ // We need a narrow condition value. It must be extended with undef elements
+ // and have the same number of elements as this shuffle.
+ unsigned NarrowNumElts = Shuf.getType()->getVectorNumElements();
+ Value *NarrowCond;
+ if (!match(Cond, m_OneUse(m_ShuffleVector(m_Value(NarrowCond), m_Undef(),
+ m_Constant()))) ||
+ NarrowCond->getType()->getVectorNumElements() != NarrowNumElts ||
+ !cast<ShuffleVectorInst>(Cond)->isIdentityWithPadding())
+ return nullptr;
+
+ // shuf (sel (shuf NarrowCond, undef, WideMask), X, Y), undef, NarrowMask) -->
+ // sel NarrowCond, (shuf X, undef, NarrowMask), (shuf Y, undef, NarrowMask)
+ Value *Undef = UndefValue::get(X->getType());
+ Value *NarrowX = Builder.CreateShuffleVector(X, Undef, Shuf.getMask());
+ Value *NarrowY = Builder.CreateShuffleVector(Y, Undef, Shuf.getMask());
+ return SelectInst::Create(NarrowCond, NarrowX, NarrowY);
+}
+
Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
Value *LHS = SVI.getOperand(0);
Value *RHS = SVI.getOperand(1);
@@ -1360,6 +1395,9 @@ Instruction *InstCombiner::visitShuffleV
if (Instruction *I = foldSelectShuffle(SVI, Builder, DL))
return I;
+ if (Instruction *I = narrowVectorSelect(SVI, Builder))
+ return I;
+
unsigned VWidth = SVI.getType()->getVectorNumElements();
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
Modified: llvm/trunk/test/Transforms/InstCombine/shuffle-select-narrow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/shuffle-select-narrow.ll?rev=341708&r1=341707&r2=341708&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/shuffle-select-narrow.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/shuffle-select-narrow.ll Fri Sep 7 14:03:34 2018
@@ -1,13 +1,13 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
-; TODO: Narrow the select operands to eliminate the existing shuffles and replace a wide select with a narrow select.
+; Narrow the select operands to eliminate the existing shuffles and replace a wide select with a narrow select.
define <2 x i8> @narrow_shuffle_of_select(<2 x i1> %cmp, <4 x i8> %x, <4 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select(
-; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
-; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x i8> [[X:%.*]], <4 x i8> [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <4 x i8> [[X:%.*]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: [[TMP2:%.*]] = shufflevector <4 x i8> [[Y:%.*]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i8> [[TMP1]], <2 x i8> [[TMP2]]
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%widecmp = shufflevector <2 x i1> %cmp, <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
@@ -31,13 +31,13 @@ define <2 x i8> @narrow_shuffle_of_selec
ret <2 x i8> %r
}
-; TODO: Verify that undef elements are acceptable for identity shuffle mask. Also check FP types.
+; Verify that undef elements are acceptable for identity shuffle mask. Also check FP types.
define <3 x float> @narrow_shuffle_of_select_undefs(<3 x i1> %cmp, <4 x float> %x, <4 x float> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_undefs(
-; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <3 x i1> [[CMP:%.*]], <3 x i1> undef, <4 x i32> <i32 undef, i32 1, i32 2, i32 undef>
-; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x float> [[X:%.*]], <4 x float> [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x float> [[WIDESEL]], <4 x float> undef, <3 x i32> <i32 0, i32 1, i32 undef>
+; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <4 x float> [[X:%.*]], <4 x float> undef, <3 x i32> <i32 0, i32 1, i32 undef>
+; CHECK-NEXT: [[TMP2:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> undef, <3 x i32> <i32 0, i32 1, i32 undef>
+; CHECK-NEXT: [[R:%.*]] = select <3 x i1> [[CMP:%.*]], <3 x float> [[TMP1]], <3 x float> [[TMP2]]
; CHECK-NEXT: ret <3 x float> [[R]]
;
%widecmp = shufflevector <3 x i1> %cmp, <3 x i1> undef, <4 x i32> <i32 undef, i32 1, i32 2, i32 undef>
@@ -49,36 +49,42 @@ define <3 x float> @narrow_shuffle_of_se
declare void @use(<4 x i8>)
declare void @use_cmp(<4 x i1>)
+; Negative test - extra use would require more instructions than we started with.
+
define <2 x i8> @narrow_shuffle_of_select_use1(<2 x i1> %cmp, <4 x i8> %x, <4 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_use1(
; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x i8> [[X:%.*]], <4 x i8> [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: call void @use(<4 x i8> [[WIDESEL]])
+; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%widecmp = shufflevector <2 x i1> %cmp, <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
%widesel = select <4 x i1> %widecmp, <4 x i8> %x, <4 x i8> %y
- %r = shufflevector <4 x i8> %widesel, <4 x i8> undef, <2 x i32> <i32 0, i32 1>
call void @use(<4 x i8> %widesel)
+ %r = shufflevector <4 x i8> %widesel, <4 x i8> undef, <2 x i32> <i32 0, i32 1>
ret <2 x i8> %r
}
+; Negative test - extra use would require more instructions than we started with.
+
define <2 x i8> @narrow_shuffle_of_select_use2(<2 x i1> %cmp, <4 x i8> %x, <4 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_use2(
; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+; CHECK-NEXT: call void @use_cmp(<4 x i1> [[WIDECMP]])
; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x i8> [[X:%.*]], <4 x i8> [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
-; CHECK-NEXT: call void @use_cmp(<4 x i1> [[WIDECMP]])
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%widecmp = shufflevector <2 x i1> %cmp, <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+ call void @use_cmp(<4 x i1> %widecmp)
%widesel = select <4 x i1> %widecmp, <4 x i8> %x, <4 x i8> %y
%r = shufflevector <4 x i8> %widesel, <4 x i8> undef, <2 x i32> <i32 0, i32 1>
- call void @use_cmp(<4 x i1> %widecmp)
ret <2 x i8> %r
}
+; Negative test - mismatched types would require extra shuffling.
+
define <3 x i8> @narrow_shuffle_of_select_mismatch_types1(<2 x i1> %cmp, <4 x i8> %x, <4 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_mismatch_types1(
; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
@@ -92,6 +98,8 @@ define <3 x i8> @narrow_shuffle_of_selec
ret <3 x i8> %r
}
+; Negative test - mismatched types would require extra shuffling.
+
define <3 x i8> @narrow_shuffle_of_select_mismatch_types2(<4 x i1> %cmp, <6 x i8> %x, <6 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_mismatch_types2(
; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <4 x i1> [[CMP:%.*]], <4 x i1> undef, <6 x i32> <i32 0, i32 1, i32 2, i32 3, i32 undef, i32 undef>
@@ -105,13 +113,11 @@ define <3 x i8> @narrow_shuffle_of_selec
ret <3 x i8> %r
}
-; TODO: Narrowing constants does not require creating new narrowing shuffle instructions.
+; Narrowing constants does not require creating new narrowing shuffle instructions.
define <2 x i8> @narrow_shuffle_of_select_consts(<2 x i1> %cmp) {
; CHECK-LABEL: @narrow_shuffle_of_select_consts(
-; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
-; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x i8> <i8 -1, i8 -2, i8 undef, i8 undef>, <4 x i8> <i8 1, i8 2, i8 undef, i8 undef>
-; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i8> <i8 -1, i8 -2>, <2 x i8> <i8 1, i8 2>
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%widecmp = shufflevector <2 x i1> %cmp, <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
@@ -121,15 +127,11 @@ define <2 x i8> @narrow_shuffle_of_selec
}
; PR38691 - https://bugs.llvm.org/show_bug.cgi?id=38691
-; TODO: If the operands are widened only to be narrowed back, then all of the shuffles are unnecessary.
+; If the operands are widened only to be narrowed back, then all of the shuffles are unnecessary.
define <2 x i8> @narrow_shuffle_of_select_with_widened_ops(<2 x i1> %cmp, <2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @narrow_shuffle_of_select_with_widened_ops(
-; CHECK-NEXT: [[WIDEX:%.*]] = shufflevector <2 x i8> [[X:%.*]], <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
-; CHECK-NEXT: [[WIDEY:%.*]] = shufflevector <2 x i8> [[Y:%.*]], <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
-; CHECK-NEXT: [[WIDECMP:%.*]] = shufflevector <2 x i1> [[CMP:%.*]], <2 x i1> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
-; CHECK-NEXT: [[WIDESEL:%.*]] = select <4 x i1> [[WIDECMP]], <4 x i8> [[WIDEX]], <4 x i8> [[WIDEY]]
-; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i8> [[WIDESEL]], <4 x i8> undef, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]
; CHECK-NEXT: ret <2 x i8> [[R]]
;
%widex = shufflevector <2 x i8> %x, <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
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