1; NOTE: Assertions have been autogenerated by utils/update_test_checks.py 2; RUN: opt < %s -O1 -S -mattr=+lzcnt | FileCheck %s 3 4target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" 5target triple = "x86_64-unknown-linux-gnu" 6 7; This test ensures we are able to optimize the following loop to an llvm.abs 8; followed by an llvm.ctlz. 9; FIXME: LoopIdiom recongize is not forming llvm.ctlz. 10 11; int ctlz_zero_check(int n) 12; { 13; n = n >= 0 ? n : -n; 14; int i = 0; 15; while(n) { 16; n >>= 1; 17; i++; 18; } 19; return i; 20; } 21 22define i32 @ctlz_loop_with_abs(i32 %n) { 23; CHECK-LABEL: @ctlz_loop_with_abs( 24; CHECK-NEXT: entry: 25; CHECK-NEXT: [[TOBOOL_NOT1:%.*]] = icmp eq i32 [[N:%.*]], 0 26; CHECK-NEXT: br i1 [[TOBOOL_NOT1]], label [[WHILE_END:%.*]], label [[WHILE_BODY_PREHEADER:%.*]] 27; CHECK: while.body.preheader: 28; CHECK-NEXT: [[TMP0:%.*]] = tail call i32 @llvm.abs.i32(i32 [[N]], i1 true) 29; CHECK-NEXT: br label [[WHILE_BODY:%.*]] 30; CHECK: while.body: 31; CHECK-NEXT: [[N_ADDR_03:%.*]] = phi i32 [ [[TMP1:%.*]], [[WHILE_BODY]] ], [ [[TMP0]], [[WHILE_BODY_PREHEADER]] ] 32; CHECK-NEXT: [[I_02:%.*]] = phi i32 [ [[INC:%.*]], [[WHILE_BODY]] ], [ 0, [[WHILE_BODY_PREHEADER]] ] 33; CHECK-NEXT: [[TMP1]] = lshr i32 [[N_ADDR_03]], 1 34; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[I_02]], 1 35; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp samesign ult i32 [[N_ADDR_03]], 2 36; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label [[WHILE_END]], label [[WHILE_BODY]] 37; CHECK: while.end: 38; CHECK-NEXT: [[I_0_LCSSA:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INC]], [[WHILE_BODY]] ] 39; CHECK-NEXT: ret i32 [[I_0_LCSSA]] 40; 41entry: 42 %cmp = icmp sge i32 %n, 0 43 br i1 %cmp, label %cond.true, label %cond.false 44 45cond.true: ; preds = %entry 46 br label %cond.end 47 48cond.false: ; preds = %entry 49 %sub = sub nsw i32 0, %n 50 br label %cond.end 51 52cond.end: ; preds = %cond.false, %cond.true 53 %cond = phi i32 [ %n, %cond.true ], [ %sub, %cond.false ] 54 br label %while.cond 55 56while.cond: ; preds = %while.body, %cond.end 57 %i.0 = phi i32 [ 0, %cond.end ], [ %inc, %while.body ] 58 %n.addr.0 = phi i32 [ %cond, %cond.end ], [ %shr, %while.body ] 59 %tobool = icmp ne i32 %n.addr.0, 0 60 br i1 %tobool, label %while.body, label %while.end 61 62while.body: ; preds = %while.cond 63 %shr = ashr i32 %n.addr.0, 1 64 %inc = add nsw i32 %i.0, 1 65 br label %while.cond 66 67while.end: ; preds = %while.cond 68 ret i32 %i.0 69} 70