[llvm] r322660 - [InstCombine] add test to show hole in demanded bits; NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Wed Jan 17 06:27:35 2018
New Revision: 322660

URL: http://llvm.org/viewvc/llvm-project?rev=322660&view=rev
Log:
[InstCombine] add test to show hole in demanded bits; NFC

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

Modified: llvm/trunk/test/Transforms/InstCombine/and.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/and.ll?rev=322660&r1=322659&r2=322660&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/and.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/and.ll Wed Jan 17 06:27:35 2018
@@ -368,6 +368,25 @@ define <2 x i32> @and_demanded_bits_spla
   ret <2 x i32> %z
 }
 
+; zext (x >> 8) has all zeros in the high 24-bits:  0x000000xx
+; (y | 255) has all ones in the low 8-bits: 0xyyyyyyff
+; 'and' of those is all known bits - it's just 'z'.
+
+define i32 @and_zext_demanded(i16 %x, i32 %y) {
+; CHECK-LABEL: @and_zext_demanded(
+; CHECK-NEXT:    [[S:%.*]] = lshr i16 %x, 8
+; CHECK-NEXT:    [[Z:%.*]] = zext i16 [[S]] to i32
+; CHECK-NEXT:    [[O:%.*]] = or i32 %y, 255
+; CHECK-NEXT:    [[A:%.*]] = and i32 [[O]], [[Z]]
+; CHECK-NEXT:    ret i32 [[A]]
+;
+  %s = lshr i16 %x, 8
+  %z = zext i16 %s to i32
+  %o = or i32 %y, 255
+  %a = and i32 %o, %z
+  ret i32 %a
+}
+
 define i32 @test32(i32 %In) {
 ; CHECK-LABEL: @test32(
 ; CHECK-NEXT:    ret i32 0