[llvm] r303755 - [InstCombine] add tests to show potential missing folds; NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Wed May 24 09:56:51 2017
New Revision: 303755

URL: http://llvm.org/viewvc/llvm-project?rev=303755&view=rev
Log:
[InstCombine] add tests to show potential missing folds; NFC

As noted in https://bugs.llvm.org/show_bug.cgi?id=33138 and
the comments, there are multiple ways to view this. If we
choose not to solve this in InstCombine, these tests will
serve as documentation of that choice.

Modified:
    llvm/trunk/test/Transforms/InstCombine/icmp-xor-signbit.ll

Modified: llvm/trunk/test/Transforms/InstCombine/icmp-xor-signbit.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp-xor-signbit.ll?rev=303755&r1=303754&r2=303755&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp-xor-signbit.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp-xor-signbit.ll Wed May 24 09:56:51 2017
@@ -187,3 +187,42 @@ define <2 x i1> @uge_to_slt_splat(<2 x i
   ret <2 x i1> %cmp
 }
 
+; PR33138, part 2: https://bugs.llvm.org/show_bug.cgi?id=33138
+; TODO: We could look through vector bitcasts for icmp folds,
+; or we could canonicalize bitcast ahead of logic ops with constants.
+
+define <8 x i1> @sgt_to_ugt_bitcasted_splat(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @sgt_to_ugt_bitcasted_splat(
+; CHECK-NEXT:    [[A:%.*]] = xor <2 x i32> %x, <i32 -2139062144, i32 -2139062144>
+; CHECK-NEXT:    [[B:%.*]] = xor <2 x i32> %y, <i32 -2139062144, i32 -2139062144>
+; CHECK-NEXT:    [[C:%.*]] = bitcast <2 x i32> [[A]] to <8 x i8>
+; CHECK-NEXT:    [[D:%.*]] = bitcast <2 x i32> [[B]] to <8 x i8>
+; CHECK-NEXT:    [[E:%.*]] = icmp sgt <8 x i8> [[C]], [[D]]
+; CHECK-NEXT:    ret <8 x i1> [[E]]
+;
+  %a = xor <2 x i32> %x, <i32 2155905152, i32 2155905152> ; 0x80808080
+  %b = xor <2 x i32> %y, <i32 2155905152, i32 2155905152>
+  %c = bitcast <2 x i32> %a to <8 x i8>
+  %d = bitcast <2 x i32> %b to <8 x i8>
+  %e = icmp sgt <8 x i8> %c, %d
+  ret <8 x i1> %e
+}
+
+; TODO: This is false (little-endian). How should that be recognized?
+; Ie, should InstSimplify know this directly, should InstCombine canonicalize
+; this so InstSimplify can know this, or is that not something that we want
+; either pass to recognize?
+
+define <2 x i1> @negative_simplify_splat(<4 x i8> %x) {
+; CHECK-LABEL: @negative_simplify_splat(
+; CHECK-NEXT:    [[A:%.*]] = or <4 x i8> %x, <i8 0, i8 -128, i8 0, i8 -128>
+; CHECK-NEXT:    [[B:%.*]] = bitcast <4 x i8> [[A]] to <2 x i16>
+; CHECK-NEXT:    [[C:%.*]] = icmp sgt <2 x i16> [[B]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[C]]
+;
+  %a = or <4 x i8> %x, <i8 0, i8 128, i8 0, i8 128>
+  %b = bitcast <4 x i8> %a to <2 x i16>
+  %c = icmp sgt <2 x i16> %b, zeroinitializer
+  ret <2 x i1> %c
+}
+