[InstCombine] Fix for PR29124: reduce insertelements to shufflevector

If inserting more than one constant into a vector:

define <4 x float> @foo(<4 x float> %x) {
  %ins1 = insertelement <4 x float> %x, float 1.0, i32 1
  %ins2 = insertelement <4 x float> %ins1, float 2.0, i32 2
  ret <4 x float> %ins2
}

InstCombine could reduce that to a shufflevector:

define <4 x float> @goo(<4 x float> %x) {
 %shuf = shufflevector <4 x float> %x, <4 x float> <float undef, float 1.0, float 2.0, float undef>, <4 x i32><i32 0, i32 5, i32 6, i32 3>
 ret <4 x float> %shuf
}
Also, InstCombine tries to convert shuffle instruction to single insertelement, if one of the vectors is a constant vector and only a single element from this constant should be used in shuffle, i.e.
shufflevector <4 x float> %v, <4 x float> <float undef, float 1.0, float
undef, float undef>, <4 x i32> <i32 0, i32 5, i32 undef, i32 undef> ->
insertelement <4 x float> %v, float 1.0, 1

Differential Revision: https://reviews.llvm.org/D24182

llvm-svn: 282237

1 files changed, 23 insertions, 6 deletions

diff --git a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
index 9b45962569a..b3e614653cf 100644
--- a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
@@ -7,10 +7,9 @@ define<4 x float> @foo(<4 x float> %x) {
   ret<4 x float> %ins2
 }
 
-; FIXME: insertelements should fold to shuffle
+; insertelements should fold to shuffle
 ; CHECK-LABEL: @foo
-; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 1.000000e+00, i32 1
-; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 2.000000e+00, i32 2
+; CHECK-NEXT: shufflevector <4 x float> %{{.+}}, <4 x float> <float undef, float 1.000000e+00, float 2.000000e+00, float undef>, <4 x i32> <i32 0, i32 5, i32 6, i32 3>
 ; CHECK-NEXT: ret <4 x float> %
 
 define<4 x float> @bar(<4 x float> %x, float %a) {
@@ -45,12 +44,11 @@ define<4 x float> @bazz(<4 x float> %x, i32 %a) {
   ret<4 x float> %ins6
 }
 
-; FIXME: insertelements should fold to shuffle
+; insertelements should fold to shuffle
 ; CHECK-LABEL: @bazz
 ; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 1.000000e+00, i32 3
 ; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 5.000000e+00, i32 %
-; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 1.000000e+00, i32 1
-; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 2.000000e+00, i32 2
+; CHECK-NEXT: shufflevector <4 x float> %{{.+}}, <4 x float> <float undef, float 1.000000e+00, float 2.000000e+00, float undef>, <4 x i32> <i32 0, i32 5, i32 6, i32 3>
 ; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 7.000000e+00, i32 %
 ; CHECK-NEXT: ret <4 x float> %
 
@@ -75,3 +73,22 @@ define<4 x float> @bazzzz(<4 x float> %x) {
 ; CHECK-NEXT: insertelement <4 x float> %{{.+}}, float 2.000000e+00, i32 2
 ; CHECK-NEXT: ret <4 x float> %
 
+define<4 x float> @bazzzzz() {
+  %ins1 = insertelement <4 x float> insertelement (<4 x float> <float 1.0, float 2.0, float 3.0, float undef>, float 4.0, i32 3), float 5.0, i32 1
+  %ins2 = insertelement<4 x float> %ins1, float 10.0, i32 2
+  ret<4 x float> %ins2
+}
+
+; insertelements should fold to shuffle
+; CHECK-LABEL: @bazzzzz
+; CHECK-NEXT: ret <4 x float> <float 1.000000e+00, float 5.000000e+00, float 1.000000e+01, float 4.000000e+00>
+
+define<4 x float> @bazzzzzz(<4 x float> %x, i32 %a) {
+  %ins1 = insertelement <4 x float> insertelement (<4 x float> shufflevector (<4 x float> undef, <4 x float> <float 1.0, float 2.0, float 3.0, float 4.0> , <4 x i32> <i32 0, i32 5, i32 undef, i32 6> ), float 4.0, i32 3), float 5.0, i32 1
+  ret<4 x float> %ins1
+}
+
+; insertelements should fold to shuffle
+; CHECK-LABEL: @bazzzzz
+; CHECK-NEXT: ret <4 x float> <float undef, float 5.000000e+00, float undef, float 4.000000e+00>
+