1; NOTE: Assertions have been autogenerated by utils/update_test_checks.py 2; RUN: opt < %s -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s 3 4; This looks like a normal sign extension, but it's not. 5; This comes up in JPEG decoding. This check is really unpredictable, 6; so it is likely beneficial to avoid the branch. 7 8define i32 @extend_value(i32 %storage, i32 %nbits) { 9; CHECK-LABEL: @extend_value( 10; CHECK-NEXT: bb: 11; CHECK-NEXT: [[SKIPNBITS:%.*]] = sub i32 32, [[NBITS:%.*]] 12; CHECK-NEXT: [[VALUE:%.*]] = lshr i32 [[STORAGE:%.*]], [[SKIPNBITS]] 13; CHECK-NEXT: [[SHOULDEXTEND:%.*]] = icmp sgt i32 [[STORAGE]], -1 14; CHECK-NEXT: [[HIGHBITMASK:%.*]] = shl nsw i32 -1, [[NBITS]] 15; CHECK-NEXT: [[HIGHBITMASKPLUSONE:%.*]] = add nsw i32 [[HIGHBITMASK]], 1 16; CHECK-NEXT: [[EXTENDED:%.*]] = add i32 [[HIGHBITMASKPLUSONE]], [[VALUE]] 17; CHECK-NEXT: [[RES:%.*]] = select i1 [[SHOULDEXTEND]], i32 [[EXTENDED]], i32 [[VALUE]] 18; CHECK-NEXT: ret i32 [[RES]] 19; 20bb: 21 %skipnbits = sub i32 32, %nbits 22 %value = lshr i32 %storage, %skipnbits 23 %shouldextend = icmp sgt i32 %storage, -1 24 br i1 %shouldextend, label %extend, label %end 25 26extend: ; preds = %bb 27 %highbitmask = shl nsw i32 -1, %nbits 28 %highbitmaskplusone = add nsw i32 %highbitmask, 1 29 %extended = add i32 %highbitmaskplusone, %value 30 br label %end 31 32end: ; preds = %extend, %bb 33 %res = phi i32 [ %extended, %extend ], [ %value, %bb ] 34 ret i32 %res 35} 36