_mm_roundscale_ss
Classification
AVX-512, Miscellaneous, CPUID Test: AVX512F
Header File
immintrin.h
Instruction
VRNDSCALESS xmm, xmm, xmm, imm8
Synopsis
 _mm_roundscale_ss(__m128 a, __m128 b, const int imm8);
Description
Round the lower single-precision (32-bit) floating-point element in "b" to the number of fraction bits specified by "imm8", store the result in the lower element of "dst", and copy the upper 3 packed elements from "a" to the upper elements of "dst". [round_imm_note]
Operation
DEFINE RoundScaleFP32(src1[31:0], imm8[7:0]) {
	m[31:0] := FP32(imm8[7:4]) // number of fraction bits after the binary point to be preserved
	tmp[31:0] := POW(FP32(2.0), -m) * ROUND(POW(FP32(2.0), m) * src1[31:0], imm8[3:0])
	IF IsInf(tmp[31:0])
		tmp[31:0] := src1[31:0]
	FI
	RETURN tmp[31:0]
}
dst[31:0] := RoundScaleFP32(b[31:0], imm8[7:0])
dst[127:32] := a[127:32]
dst[MAX:128] := 0