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[NFC] Add test that shows that InstCombine can do better

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llvm-svn: 336258
This commit is contained in:
Max Kazantsev 2018-07-04 10:32:02 +00:00
parent 6f5c420176
commit 97daf8f423
1 changed files with 24 additions and 0 deletions
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24
test/Transforms/InstCombine/max_known_bits.ll Normal file
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -instcombine < %s | FileCheck %s
; TODO: The entire thing should be folded to and i16 %0, 255.
define i16 @foo(i16 ) {
; CHECK-LABEL: @foo(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP1:%.*]] = and i16 [[TMP0:%.*]], 255
; CHECK-NEXT: [[TMP2:%.*]] = zext i16 [[TMP1]] to i32
; CHECK-NEXT: [[TMP3:%.*]] = icmp ult i32 [[TMP2]], 255
; CHECK-NEXT: [[TMP4:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 255
; CHECK-NEXT: [[TMP5:%.*]] = trunc i32 [[TMP4]] to i16
; CHECK-NEXT: [[TMP6:%.*]] = and i16 [[TMP5]], 255
; CHECK-NEXT: ret i16 [[TMP6]]
;
entry:
%1 = and i16 %0, 255
%2 = zext i16 %1 to i32
%3 = icmp ult i32 %2, 255
%4 = select i1 %3, i32 %2, i32 255
%5 = trunc i32 %4 to i16
%6 = and i16 %5, 255
ret i16 %6
}