InstCombine: Fold more shuffles of shuffles.

Always fold a shuffle-of-shuffle into a single shuffle when there's only one
input vector in the first place. Continue to be more conservative when there's
multiple inputs.

rdar://13402653
PR15866

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180802 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 10 insertions, 11 deletions

diff --git a/test/Transforms/BBVectorize/simple.ll b/test/Transforms/BBVectorize/simple.ll
index a447908..a22ad15 100644
--- a/test/Transforms/BBVectorize/simple.ll
+++ b/test/Transforms/BBVectorize/simple.ll
@@ -139,11 +139,10 @@ define <8 x i8> @test6(<8 x i8> %A1, <8 x i8> %A2, <8 x i8> %B1, <8 x i8> %B2) {
 ; CHECK: %Z1 = add <16 x i8> %Y1, %X1.v.i1
         %Q1 = shufflevector <8 x i8> %Z1, <8 x i8> %Z2, <8 x i32> <i32 15, i32 8, i32 6, i32 1, i32 13, i32 10, i32 4, i32 3>
         %Q2 = shufflevector <8 x i8> %Z2, <8 x i8> %Z2, <8 x i32> <i32 6, i32 7, i32 0, i32 1, i32 2, i32 4, i32 4, i32 1>
-; CHECK: %Q1.v.i1 = shufflevector <16 x i8> %Z1, <16 x i8> undef, <16 x i32> <i32 8, i32 undef, i32 10, i32 undef, i32 undef, i32 13, i32 undef, i32 15, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
-; CHECK: %Q1 = shufflevector <16 x i8> %Z1, <16 x i8> %Q1.v.i1, <16 x i32> <i32 23, i32 16, i32 6, i32 1, i32 21, i32 18, i32 4, i32 3, i32 14, i32 15, i32 8, i32 9, i32 10, i32 12, i32 12, i32 9>
-	%R  = mul <8 x i8> %Q1, %Q2
-; CHECK: %Q1.v.r1 = shufflevector <16 x i8> %Q1, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
-; CHECK: %Q1.v.r2 = shufflevector <16 x i8> %Q1, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+        %R  = mul <8 x i8> %Q1, %Q2
+; CHECK:  %Q1.v.i1 = shufflevector <16 x i8> %Z1, <16 x i8> undef, <16 x i32> <i32 8, i32 undef, i32 10, i32 undef, i32 undef, i32 13, i32 undef, i32 15, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+; CHECK:  %Q1.v.r1 = shufflevector <16 x i8> %Z1, <16 x i8> %Q1.v.i1, <8 x i32> <i32 23, i32 16, i32 6, i32 1, i32 21, i32 18, i32 4, i32 3>
+; CHECK:  %Q1.v.r2 = shufflevector <16 x i8> %Z1, <16 x i8> undef, <8 x i32> <i32 14, i32 15, i32 8, i32 9, i32 10, i32 12, i32 12, i32 9>
 ; CHECK: %R = mul <8 x i8> %Q1.v.r1, %Q1.v.r2
 	ret <8 x i8> %R
 ; CHECK: ret <8 x i8> %R
diff --git a/test/Transforms/InstCombine/vec_shuffle.ll b/test/Transforms/InstCombine/vec_shuffle.ll
index 37d4d56..37c19f1 100644
--- a/test/Transforms/InstCombine/vec_shuffle.ll
+++ b/test/Transforms/InstCombine/vec_shuffle.ll
@@ -86,14 +86,14 @@ define <4 x i8> @test9(<16 x i8> %tmp6) nounwind {
 }
 
 ; Same as test9, but make sure that "undef" mask values are not confused with
-; mask values of 2*N, where N is the mask length.  These shuffles should not
-; be folded (because [8,9,4,8] may not be a mask supported by the target).
-define <4 x i8> @test9a(<16 x i8> %tmp6) nounwind {
+; mask values of 2*N, where N is the mask length of the result.  Make sure when
+; folding these shuffles that 'undef' mask values stay that way in the result
+; instead of getting mapped to the 2*N'th entry of the source.
+define <4 x i8> @test9a(<16 x i8> %in, <16 x i8> %in2) nounwind {
 ; CHECK: @test9a
-; CHECK-NEXT: shufflevector
-; CHECK-NEXT: shufflevector
+; CHECK-NEXT: shufflevector <16 x i8> %in, <16 x i8> %in2, <4 x i32> <i32 16, i32 9, i32 4, i32 undef>
 ; CHECK-NEXT: ret
-	%tmp7 = shufflevector <16 x i8> %tmp6, <16 x i8> undef, <4 x i32> < i32 undef, i32 9, i32 4, i32 8 >		; <<4 x i8>> [#uses=1]
+	%tmp7 = shufflevector <16 x i8> %in, <16 x i8> %in2, <4 x i32> < i32 undef, i32 9, i32 4, i32 16 >		; <<4 x i8>> [#uses=1]
 	%tmp9 = shufflevector <4 x i8> %tmp7, <4 x i8> undef, <4 x i32> < i32 3, i32 1, i32 2, i32 0 >		; <<4 x i8>> [#uses=1]
 	ret <4 x i8> %tmp9
 }