Zig 0.17.0-dev (Split by item)

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__clzsi2_thumb1

count0bits.__clzsi2_thumb1

fn __clzsi2_thumb1() callconv(.naked) void

File

lib/compiler_rt/count0bits.zig:52

Code

fn __clzsi2_thumb1() callconv(.naked) void {
    @setRuntimeSafety(false);

    // Similar to the generic version with the last two rounds replaced by a LUT
    asm volatile (
        \\ movs r1, #32
        \\ lsrs r2, r0, #16
        \\ beq 1f
        \\ subs r1, #16
        \\ movs r0, r2
        \\ 1:
        \\ lsrs r2, r0, #8
        \\ beq 1f
        \\ subs r1, #8
        \\ movs r0, r2
        \\ 1:
        \\ lsrs r2, r0, #4
        \\ beq 1f
        \\ subs r1, #4
        \\ movs r0, r2
        \\ 1:
        \\ adr r3, .lut
        \\ ldrb r0, [r3, r0]
        \\ subs r0, r1, r0
        \\ bx lr
        \\ .p2align 2
        \\ // Number of bits set in the 0-15 range
        \\ .lut:
        \\ .byte 0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4
    );

    unreachable;
}