[llvm] r353233 - [InstCombine] split shuffle test to show extra use constraint; NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Tue Feb  5 14:46:13 2019
New Revision: 353233

URL: http://llvm.org/viewvc/llvm-project?rev=353233&view=rev
Log:
[InstCombine] split shuffle test to show extra use constraint; NFC

As discussed in D53037, this transform can cause codegen problems
if the 1st shuffle has multiple uses.

Modified:
    llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll

Modified: llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll?rev=353233&r1=353232&r2=353233&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/vec_shuffle.ll Tue Feb  5 14:46:13 2019
@@ -182,10 +182,21 @@ define <2 x i8> @extract_subvector_of_sh
   ret <2 x i8> %extract_subv
 }
 
-; Extra uses are ok.
 ; Undef elements in either mask are ok. Undefs from the 2nd shuffle mask should propagate to the new shuffle.
 ; The type of the inputs does not have to match the output type.
 
+define <4 x i8> @extract_subvector_of_shuffle_undefs_types(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @extract_subvector_of_shuffle_undefs_types(
+; CHECK-NEXT:    [[EXTRACT_SUBV:%.*]] = shufflevector <2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]], <4 x i32> <i32 undef, i32 2, i32 0, i32 undef>
+; CHECK-NEXT:    ret <4 x i8> [[EXTRACT_SUBV]]
+;
+  %shuf = shufflevector <2 x i8> %x, <2 x i8> %y, <5 x i32> <i32 undef, i32 2, i32 0, i32 1, i32 0>
+  %extract_subv = shufflevector <5 x i8> %shuf, <5 x i8> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 undef>
+  ret <4 x i8> %extract_subv
+}
+
+; FIXME: Extra uses are not ok - we should only do the transform when we can eliminate an instruction.
+
 declare void @use_v5i8(<5 x i8>)
 
 define <4 x i8> @extract_subvector_of_shuffle_extra_use(<2 x i8> %x, <2 x i8> %y) {
@@ -723,8 +734,8 @@ define <8 x i8> @pr19730(<16 x i8> %in0)
 
 define i32 @pr19737(<4 x i32> %in0) {
 ; CHECK-LABEL: @pr19737(
-; CHECK-NEXT:    [[RV_RHS:%.*]] = extractelement <4 x i32> [[IN0:%.*]], i32 0
-; CHECK-NEXT:    ret i32 [[RV_RHS]]
+; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <4 x i32> [[IN0:%.*]], i32 0
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %shuffle.i = shufflevector <4 x i32> zeroinitializer, <4 x i32> %in0, <4 x i32> <i32 0, i32 4, i32 2, i32 6>
   %neg.i = xor <4 x i32> %shuffle.i, <i32 -1, i32 -1, i32 -1, i32 -1>