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 is the naive implementation of x86 BZHI/BEXTR instruction: 5; it takes input and bit count, and extracts low nbits up to bit width. 6; I.e. unlike shift it does not have any UB when nbits >= bitwidth. 7; Which means we don't need a while PHI here, simple select will do. 8define i32 @extract_low_bits(i32 %input, i32 %nbits) { 9; CHECK-LABEL: @extract_low_bits( 10; CHECK-NEXT: begin: 11; CHECK-NEXT: [[SHOULD_MASK:%.*]] = icmp ult i32 [[NBITS:%.*]], 32 12; CHECK-NEXT: [[MASK_NOT:%.*]] = shl nsw i32 -1, [[NBITS]] 13; CHECK-NEXT: [[MASK:%.*]] = xor i32 [[MASK_NOT]], -1 14; CHECK-NEXT: [[MASKED:%.*]] = and i32 [[MASK]], [[INPUT:%.*]] 15; CHECK-NEXT: [[RES:%.*]] = select i1 [[SHOULD_MASK]], i32 [[MASKED]], i32 [[INPUT]] 16; CHECK-NEXT: ret i32 [[RES]] 17; 18begin: 19 %should_mask = icmp ult i32 %nbits, 32 20 br i1 %should_mask, label %perform_masking, label %end 21 22perform_masking: ; preds = %begin 23 %mask.not = shl nsw i32 -1, %nbits 24 %mask = xor i32 %mask.not, -1 25 %masked = and i32 %mask, %input 26 br label %end 27 28end: ; preds = %perform_masking, %begin 29 %res = phi i32 [ %masked, %perform_masking ], [ %input, %begin ] 30 ret i32 %res 31} 32