1;; This tests lowering of the implementations of table-based ctz 2;; algorithm to the llvm.cttz instruction in the -O3 case. 3 4;; C producer: 5;; int ctz1 (unsigned x) 6;; { 7;; static const char table[32] = 8;; { 9;; 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, 10;; 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 11;; }; 12;; return table[((unsigned)((x & -x) * 0x077CB531U)) >> 27]; 13;; } 14;; Compiled as: clang -O3 test.c -S -emit-llvm -Xclang -disable-llvm-optzns 15 16; RUN: opt -O3 -S < %s | FileCheck %s 17 18; CHECK: call range(i32 0, 33) i32 @llvm.cttz.i32 19 20@ctz1.table = internal constant [32 x i8] c"\00\01\1C\02\1D\0E\18\03\1E\16\14\0F\19\11\04\08\1F\1B\0D\17\15\13\10\07\1A\0C\12\06\0B\05\0A\09", align 16 21 22define i32 @ctz1(i32 noundef %x) { 23entry: 24 %x.addr = alloca i32, align 4 25 store i32 %x, ptr %x.addr, align 4 26 %0 = load i32, ptr %x.addr, align 4 27 %1 = load i32, ptr %x.addr, align 4 28 %sub = sub i32 0, %1 29 %and = and i32 %0, %sub 30 %mul = mul i32 %and, 125613361 31 %shr = lshr i32 %mul, 27 32 %idxprom = zext i32 %shr to i64 33 %arrayidx = getelementptr inbounds [32 x i8], ptr @ctz1.table, i64 0, i64 %idxprom 34 %2 = load i8, ptr %arrayidx, align 1 35 %conv = sext i8 %2 to i32 36 ret i32 %conv 37} 38