# VMAXSH — Return Maximum of Scalar FP16 Values

Instruction En bit Mode Flag Support Instruction En bit Mode Flag Support 64/32 CPUID Feature Instruction En bit Mode Flag CPUID Feature Instruction En bit Mode Flag Op/ 64/32 CPUID Feature Instruction En bit Mode Flag 64/32 CPUID Feature Instruction En bit Mode Flag CPUID Feature Instruction En bit Mode Flag Op/ 64/32 CPUID Feature |  | Support |  | Description
--- | --- | --- | --- | ---
EVEX.LLIG.F3.MAP5.W0 5F /r VMAXSH xmm1{k1}{z}, xmm2, xmm3/m16 {sae} | A | V/V | AVX512-FP16 | Return the maximum low FP16 value between xmm3/m16 and xmm2 and store the result in xmm1 subject to writemask k1. Bits 127:16 of xmm2 are copied to xmm1[127:16].

## Instruction Operand Encoding ¶

Op/En | Tuple | Operand 1 | Operand 2 | Operand 3 | Operand 4
--- | --- | --- | --- | --- | ---
A | Scalar | ModRM:reg (w) | VEX.vvvv (r) | ModRM:r/m (r) | N/A

### Description ¶

This instruction performs a compare of the low packed FP16 values in the first source operand and the second source operand and returns the maximum value for the pair of values to the destination operand.

If the values being compared are both 0.0s (of either sign), the value in the second operand (source operand) is returned. If a value in the second operand is an SNaN, then SNaN is forwarded unchanged to the destination (that is, a QNaN version of the SNaN is not returned).

If only one value is a NaN (SNaN or QNaN) for this instruction, the second operand (source operand), either a NaN or a valid floating-point value, is written to the result. If instead of this behavior, it is required that the NaN source operand (from either the first or second operand) be returned, the action of VMAXSH can be emulated using a sequence of instructions, such as, a comparison followed by AND, ANDN, and OR.

Bits 127:16 of the destination operand are copied from the corresponding bits of the first source operand. Bits MAXVL-1:128 of the destination operand are zeroed. The low FP16 element of the destination is updated according to the writemask.

### Operation ¶

    def MAX(SRC1, SRC2):
        IF (SRC1 = 0.0) and (SRC2 = 0.0):
            DEST := SRC2
        ELSE IF (SRC1 = NaN):
            DEST := SRC2
        ELSE IF (SRC2 = NaN):
            DEST := SRC2
        ELSE IF (SRC1 > SRC2):
            DEST := SRC1
        ELSE:
            DEST := SRC2

#### VMAXSH dest, src1, src2 ¶

    IF k1[0] OR *no writemask*:
        DEST.fp16[0] := MAX(SRC1.fp16[0], SRC2.fp16[0])
    ELSE IF *zeroing*:
        DEST.fp16[0] := 0
    // else dest.fp16[j] remains unchanged
    DEST[127:16] := SRC1[127:16]
    DEST[MAXVL-1:128] := 0

### Intel C/C++ Compiler Intrinsic Equivalent ¶

    VMAXSH __m128h _mm_mask_max_round_sh (__m128h src, __mmask8 k, __m128h a, __m128h b, int sae);

    VMAXSH __m128h _mm_maskz_max_round_sh (__mmask8 k, __m128h a, __m128h b, int sae);

    VMAXSH __m128h _mm_max_round_sh (__m128h a, __m128h b, int sae);

    VMAXSH __m128h _mm_mask_max_sh (__m128h src, __mmask8 k, __m128h a, __m128h b);

    VMAXSH __m128h _mm_maskz_max_sh (__mmask8 k, __m128h a, __m128h b);

    VMAXSH __m128h _mm_max_sh (__m128h a, __m128h b);

### SIMD Floating-Point Exceptions ¶

Invalid, Denormal

### Other Exceptions ¶

EVEX-encoded instructions, see Table 2-47, “Type E3 Class Exception Conditions.”