MAXPS

Maximum of Packed Single Precision Floating-Point Values

stableVMJITAOTinstruction

Encodings

Operand encoding

Each mode is a value of the Op/En column above. It says which field of the encoded instruction carries each operand, in the order they are written, and whether the instruction reads it, writes it or both.

Measured cost

Description#

Performs a SIMD compare of the packed single precision floating-point values in the first source operand and the second source operand and returns the maximum value for each 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 MAXPS can be emulated using a sequence of instructions, such as, a comparison followed by AND, ANDN, and OR.

EVEX encoded versions: The first source operand (the second operand) is a ZMM/YMM/XMM register. The second source operand can be a ZMM/YMM/XMM register, a 512/256/128-bit memory location or a 512/256/128-bit vector broadcasted from a 32-bit memory location. The destination operand is a ZMM/YMM/XMM register conditionally updated with writemask k1.

VEX.256 encoded version: The first source operand is a YMM register. The second source operand can be a YMM register or a 256-bit memory location. The destination operand is a YMM register. The upper bits (MAXVL-1:256) of the corresponding ZMM register destination are zeroed.

VEX.128 encoded version: The first source operand is a XMM register. The second source operand can be a XMM register or a 128-bit memory location. The destination operand is a XMM register. The upper bits (MAXVL-1:128) of the corresponding ZMM register destination are zeroed.

128-bit Legacy SSE version: The second source can be an XMM register or an 128-bit memory location. The destination is not distinct from the first source XMM register and the upper bits (MAXVL-1:128) of the corresponding ZMM register destination are unmodified.

Operation#

MAX(SRC1, SRC2)
{

    IF ((SRC1 = 0.0) and (SRC2 = 0.0)) THEN DEST := SRC2;
          ELSE IF (SRC1 = NaN) THEN DEST := SRC2; FI;
          ELSE IF (SRC2 = NaN) THEN DEST := SRC2; FI;
          ELSE IF (SRC1 > SRC2) THEN DEST := SRC1;
          ELSE DEST := SRC2;

    FI;
}

VMAXPS (EVEX Encoded Versions)

(KL, VL) = (4, 128), (8, 256), (16, 512)

FOR j := 0 TO KL-1

i := j * 32

IF k1[j] OR *no writemask*

     THEN

             IF (EVEX.b = 1) AND (SRC2 *is memory*)

                  THEN

                    DEST[i+31:i] := MAX(SRC1[i+31:i], SRC2[31:0])

                  ELSE

                    DEST[i+31:i] := MAX(SRC1[i+31:i], SRC2[i+31:i])

             FI;

     ELSE

             IF *merging-masking*         ; merging-masking

                  THEN *DEST[i+31:i] remains unchanged*

                  ELSE DEST[i+31:i] := 0  ; zeroing-masking

             FI

FI;

ENDFOR

DEST[MAXVL-1:VL] := 0

VMAXPS (VEX.256 Encoded Version)
DEST[31:0] := MAX(SRC1[31:0], SRC2[31:0])
DEST[63:32] := MAX(SRC1[63:32], SRC2[63:32])
DEST[95:64] := MAX(SRC1[95:64], SRC2[95:64])
DEST[127:96] := MAX(SRC1[127:96], SRC2[127:96])
DEST[159:128] := MAX(SRC1[159:128], SRC2[159:128])
DEST[191:160] := MAX(SRC1[191:160], SRC2[191:160])
DEST[223:192] := MAX(SRC1[223:192], SRC2[223:192])
DEST[255:224] := MAX(SRC1[255:224], SRC2[255:224])
DEST[MAXVL-1:256] := 0


VMAXPS (VEX.128 Encoded Version)
DEST[31:0] := MAX(SRC1[31:0], SRC2[31:0])
DEST[63:32] := MAX(SRC1[63:32], SRC2[63:32])
DEST[95:64] := MAX(SRC1[95:64], SRC2[95:64])
DEST[127:96] := MAX(SRC1[127:96], SRC2[127:96])
DEST[MAXVL-1:128] := 0

MAXPS (128-bit Legacy SSE Version)
DEST[31:0] := MAX(DEST[31:0], SRC[31:0])
DEST[63:32] := MAX(DEST[63:32], SRC[63:32])
DEST[95:64] := MAX(DEST[95:64], SRC[95:64])
DEST[127:96] := MAX(DEST[127:96], SRC[127:96])
DEST[MAXVL-1:128] (Unmodified)

Intel C/C++ compiler intrinsics#

VMAXPS __m512 _mm512_max_ps( __m512 a, __m512 b);
VMAXPS __m512 _mm512_mask_max_ps(__m512 s, __mmask16 k, __m512 a, __m512 b);
VMAXPS __m512 _mm512_maskz_max_ps( __mmask16 k, __m512 a, __m512 b);
VMAXPS __m512 _mm512_max_round_ps( __m512 a, __m512 b, int);
VMAXPS __m512 _mm512_mask_max_round_ps(__m512 s, __mmask16 k, __m512 a, __m512 b, int);
VMAXPS __m512 _mm512_maskz_max_round_ps( __mmask16 k, __m512 a, __m512 b, int);
VMAXPS __m256 _mm256_mask_max_ps(__m256 s, __mmask8 k, __m256 a, __m256 b);
VMAXPS __m256 _mm256_maskz_max_ps( __mmask8 k, __m256 a, __m256 b);
VMAXPS __m128 _mm_mask_max_ps(__m128 s, __mmask8 k, __m128 a, __m128 b);
VMAXPS __m128 _mm_maskz_max_ps( __mmask8 k, __m128 a, __m128 b);
VMAXPS __m256 _mm256_max_ps (__m256 a, __m256 b);
MAXPS __m128 _mm_max_ps (__m128 a, __m128 b);

SIMD Floating-Point Exceptions#

Invalid (including QNaN Source Operand), Denormal.

Other Exceptions#

Non-EVEX-encoded instruction, see Table 2-19, "Type 2 Class Exception Conditions."

EVEX-encoded instruction, see Table 2-48, "Type E2 Class Exception Conditions."

Sources

• This instruction in the Intel manual
• Latency and throughput per microarchitecture