[InstCombine] canonicalize insertelement of scalar constant ahead of insertelement...

insertelement (insertelement X, Y, IdxC1), ScalarC, IdxC2 -->
insertelement (insertelement X, ScalarC, IdxC2), Y, IdxC1

As noted in the code comment and seen in the test changes, the motivation is that by pulling
constant insertion up, we may be able to constant fold some insertelement instructions.

Differential Revision: https://reviews.llvm.org/D31196

llvm-svn: 298520

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 10f03c4bdd88350f46e835bd8ee0ded1b7adf465..c29d3276526589cd4dd501fc7817d09cd6494520 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -645,6 +645,36 @@ static Instruction *foldInsSequenceIntoBroadcast(InsertElementInst &InsElt) {
   return new ShuffleVectorInst(InsertFirst, UndefValue::get(VT), ZeroMask);
 }
 
+/// If we have an insertelement instruction feeding into another insertelement
+/// and the 2nd is inserting a constant into the vector, canonicalize that
+/// constant insertion before the insertion of a variable:
+///
+/// insertelement (insertelement X, Y, IdxC1), ScalarC, IdxC2 -->
+/// insertelement (insertelement X, ScalarC, IdxC2), Y, IdxC1
+///
+/// This has the potential of eliminating the 2nd insertelement instruction
+/// via constant folding of the scalar constant into a vector constant.
+static Instruction *hoistInsEltConst(InsertElementInst &InsElt2,
+                                     InstCombiner::BuilderTy &Builder) {
+  auto *InsElt1 = dyn_cast<InsertElementInst>(InsElt2.getOperand(0));
+  if (!InsElt1 || !InsElt1->hasOneUse())
+    return nullptr;
+
+  Value *X, *Y;
+  Constant *ScalarC;
+  ConstantInt *IdxC1, *IdxC2;
+  if (match(InsElt1->getOperand(0), m_Value(X)) &&
+      match(InsElt1->getOperand(1), m_Value(Y)) && !isa<Constant>(Y) &&
+      match(InsElt1->getOperand(2), m_ConstantInt(IdxC1)) &&
+      match(InsElt2.getOperand(1), m_Constant(ScalarC)) &&
+      match(InsElt2.getOperand(2), m_ConstantInt(IdxC2)) && IdxC1 != IdxC2) {
+    Value *NewInsElt1 = Builder.CreateInsertElement(X, ScalarC, IdxC2);
+    return InsertElementInst::Create(NewInsElt1, Y, IdxC1);
+  }
+
+  return nullptr;
+}
+
 /// insertelt (shufflevector X, CVec, Mask|insertelt X, C1, CIndex1), C, CIndex
 /// --> shufflevector X, CVec', Mask'
 static Instruction *foldConstantInsEltIntoShuffle(InsertElementInst &InsElt) {
@@ -806,6 +836,9 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
   if (Instruction *Shuf = foldConstantInsEltIntoShuffle(IE))
     return Shuf;
 
+  if (Instruction *NewInsElt = hoistInsEltConst(IE, *Builder))
+    return NewInsElt;
+
   // Turn a sequence of inserts that broadcasts a scalar into a single
   // insert + shufflevector.
   if (Instruction *Broadcast = foldInsSequenceIntoBroadcast(IE))

diff --git a/llvm/test/Transforms/InstCombine/bitcast-bigendian.ll b/llvm/test/Transforms/InstCombine/bitcast-bigendian.ll
index 1a91d11d8aeed54d1a801b0db2b522013ca4bd7f..a6b2ac85c9c25bfe779338d91a801ebac83eaa1a 100644 (file)
--- a/llvm/test/Transforms/InstCombine/bitcast-bigendian.ll
+++ b/llvm/test/Transforms/InstCombine/bitcast-bigendian.ll
@@ -81,9 +81,8 @@ define <2 x float> @test5(float %A, float %B) {
 
 define <2 x float> @test6(float %A){
 ; CHECK-LABEL: @test6(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x float> undef, float %A, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x float> [[TMP1]], float 4.200000e+01, i32 1
-; CHECK-NEXT:    ret <2 x float> [[TMP2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x float> <float undef, float 4.200000e+01>, float %A, i32 0
+; CHECK-NEXT:    ret <2 x float> [[TMP1]]
 ;
   %tmp23 = bitcast float %A to i32
   %tmp24 = zext i32 %tmp23 to i64

diff --git a/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll b/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
index 4507deb7f023a78873df235e5e46633aaa153990..29f774c5f62b5b191632481a796d5d9267769d8a 100644 (file)
--- a/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll
@@ -86,11 +86,8 @@ define <8 x float> @widen_extract4(<8 x float> %ins, <2 x float> %ext) {
 
 define <8 x i16> @pr26015(<4 x i16> %t0) {
 ; CHECK-LABEL: @pr26015(
-; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x i16> %t0, <4 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
-; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <4 x i16> %t0, i32 2
-; CHECK-NEXT:    [[T2:%.*]] = insertelement <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 undef, i16 undef>, i16 [[TMP2]], i32 3
-; CHECK-NEXT:    [[T3:%.*]] = insertelement <8 x i16> [[T2]], i16 0, i32 6
-; CHECK-NEXT:    [[T5:%.*]] = shufflevector <8 x i16> [[T3]], <8 x i16> [[TMP1]], <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 11>
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x i16> %t0, <4 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 2, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
+; CHECK-NEXT:    [[T5:%.*]] = shufflevector <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 0, i16 undef>, <8 x i16> [[TMP1]], <8 x i32> <i32 0, i32 1, i32 2, i32 10, i32 4, i32 5, i32 6, i32 11>
 ; CHECK-NEXT:    ret <8 x i16> [[T5]]
 ;
   %t1 = extractelement <4 x i16> %t0, i32 2
@@ -110,8 +107,7 @@ define <8 x i16> @pr25999(<4 x i16> %t0, i1 %b) {
 ; CHECK-NEXT:    br i1 %b, label %if, label %end
 ; CHECK:       if:
 ; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x i16> %t0, <4 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
-; CHECK-NEXT:    [[T2:%.*]] = insertelement <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 undef, i16 undef>, i16 [[T1]], i32 3
-; CHECK-NEXT:    [[T3:%.*]] = insertelement <8 x i16> [[T2]], i16 0, i32 6
+; CHECK-NEXT:    [[T3:%.*]] = insertelement <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 0, i16 undef>, i16 [[T1]], i32 3
 ; CHECK-NEXT:    [[T5:%.*]] = shufflevector <8 x i16> [[T3]], <8 x i16> [[TMP1]], <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 11>
 ; CHECK-NEXT:    ret <8 x i16> [[T5]]
 ; CHECK:       end:

diff --git a/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll b/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll
index e29c9eef74a4d6333c21ea6d463c34e157596464..5f27634da19cc8da57aaa77ce69d5505a8ab5849 100644 (file)
--- a/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll
+++ b/llvm/test/Transforms/InstCombine/vec_demanded_elts.ll
@@ -182,10 +182,9 @@ define <4 x float> @dead_shuffle_elt(<4 x float> %x, <2 x float> %y) nounwind {
 
 define <2 x float> @test_fptrunc(double %f) {
 ; CHECK-LABEL: @test_fptrunc(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x double> undef, double %f, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x double> [[TMP1]], double 0.000000e+00, i32 1
-; CHECK-NEXT:    [[TMP3:%.*]] = fptrunc <2 x double> [[TMP2]] to <2 x float>
-; CHECK-NEXT:    ret <2 x float> [[TMP3]]
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x double> <double undef, double 0.000000e+00>, double %f, i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = fptrunc <2 x double> [[TMP1]] to <2 x float>
+; CHECK-NEXT:    ret <2 x float> [[TMP2]]
 ;
   %tmp9 = insertelement <4 x double> undef, double %f, i32 0
   %tmp10 = insertelement <4 x double> %tmp9, double 0.000000e+00, i32 1
@@ -198,10 +197,9 @@ define <2 x float> @test_fptrunc(double %f) {
 
 define <2 x double> @test_fpext(float %f) {
 ; CHECK-LABEL: @test_fpext(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x float> undef, float %f, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x float> [[TMP1]], float 0.000000e+00, i32 1
-; CHECK-NEXT:    [[TMP3:%.*]] = fpext <2 x float> [[TMP2]] to <2 x double>
-; CHECK-NEXT:    ret <2 x double> [[TMP3]]
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x float> <float undef, float 0.000000e+00>, float %f, i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = fpext <2 x float> [[TMP1]] to <2 x double>
+; CHECK-NEXT:    ret <2 x double> [[TMP2]]
 ;
   %tmp9 = insertelement <4 x float> undef, float %f, i32 0
   %tmp10 = insertelement <4 x float> %tmp9, float 0.000000e+00, i32 1
@@ -223,8 +221,7 @@ define <4 x double> @test_shuffle(<4 x double> %f) {
 
 define <4 x float> @test_select(float %f, float %g) {
 ; CHECK-LABEL: @test_select(
-; CHECK-NEXT:    [[A0:%.*]] = insertelement <4 x float> undef, float %f, i32 0
-; CHECK-NEXT:    [[A3:%.*]] = insertelement <4 x float> [[A0]], float 3.000000e+00, i32 3
+; CHECK-NEXT:    [[A3:%.*]] = insertelement <4 x float> <float undef, float undef, float undef, float 3.000000e+00>, float %f, i32 0
 ; CHECK-NEXT:    [[RET:%.*]] = shufflevector <4 x float> [[A3]], <4 x float> <float undef, float 4.000000e+00, float 5.000000e+00, float undef>, <4 x i32> <i32 0, i32 5, i32 6, i32 3>
 ; CHECK-NEXT:    ret <4 x float> [[RET]]
 ;

diff --git a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
index 8db937a9a344b72d7ee5fbf97f218799c1fe4e71..c358509d690e9b19b47bbc6ec7d3f2383688b9bc 100644 (file)
--- a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
@@ -12,10 +12,12 @@ define <4 x float> @foo(<4 x float> %x) {
   ret <4 x float> %ins2
 }
 
+; Insert of a constant is canonicalized ahead of insert of a variable.
+
 define <4 x float> @bar(<4 x float> %x, float %a) {
 ; CHECK-LABEL: @bar(
-; CHECK-NEXT:    [[INS1:%.*]] = insertelement <4 x float> %x, float %a, i32 1
-; CHECK-NEXT:    [[INS2:%.*]] = insertelement <4 x float> [[INS1]], float 2.000000e+00, i32 2
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <4 x float> %x, float 2.000000e+00, i32 2
+; CHECK-NEXT:    [[INS2:%.*]] = insertelement <4 x float> [[TMP1]], float %a, i32 1
 ; CHECK-NEXT:    ret <4 x float> [[INS2]]
 ;
   %ins1 = insertelement<4 x float> %x, float %a, i32 1