MOVSS

Move or Merge Scalar Single Precision Floating-Point Value

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#

Moves a scalar single precision floating-point value from the source operand (second operand) to the destination operand (first operand). The source and destination operands can be XMM registers or 32-bit memory locations. This instruction can be used to move a single precision floating-point value to and from the low doubleword of an XMM register and a 32-bit memory location, or to move a single precision floating-point value between the low doublewords of two XMM registers. The instruction cannot be used to transfer data between memory locations.

Legacy version: When the source and destination operands are XMM registers, bits (MAXVL-1:32) of the corresponding destination register are unmodified. When the source operand is a memory location and destination

operand is an XMM registers, Bits (127:32) of the destination operand is cleared to all 0s, bits MAXVL:128 of the destination operand remains unchanged.

VEX and EVEX encoded register-register syntax: Moves a scalar single precision floating-point value from the second source operand (the third operand) to the low doubleword element of the destination operand (the first operand). Bits 127:32 of the destination operand are copied from the first source operand (the second operand). Bits (MAXVL-1:128) of the corresponding destination register are zeroed.

VEX and EVEX encoded memory load syntax: When the source operand is a memory location and destination operand is an XMM registers, bits MAXVL:32 of the destination operand is cleared to all 0s.

EVEX encoded versions: The low doubleword of the destination is updated according to the writemask.

Note: For memory store form instruction "VMOVSS m32, xmm1", VEX.vvvv is reserved and must be 1111b otherwise instruction will #UD. For memory store form instruction "VMOVSS mv {k1}, xmm1", EVEX.vvvv is reserved and must be 1111b otherwise instruction will #UD.

Software should ensure VMOVSS is encoded with VEX.L=0. Encoding VMOVSS with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation#

VMOVSS (EVEX.LLIG.F3.0F.W0 11 /r When the Source Operand is Memory and the Destination is an XMM Register)

IF k1[0] or *no writemask*

     THEN DEST[31:0] := SRC[31:0]

     ELSE

     IF *merging-masking*           ; merging-masking

           THEN *DEST[31:0] remains unchanged*

           ELSE                     ; zeroing-masking

           THEN DEST[31:0] := 0

     FI;

FI;

DEST[MAXVL-1:32] := 0

VMOVSS (EVEX.LLIG.F3.0F.W0 10 /r When the Source Operand is an XMM Register and the Destination is Memory)

IF k1[0] or *no writemask*

     THEN DEST[31:0] := SRC[31:0]

     ELSE *DEST[31:0] remains unchanged*        ; merging-masking

FI;

VMOVSS (EVEX.LLIG.F3.0F.W0 10/11 /r Where the Source and Destination are XMM Registers)

IF k1[0] or *no writemask*

     THEN DEST[31:0] := SRC2[31:0]

     ELSE

     IF *merging-masking*           ; merging-masking

           THEN *DEST[31:0] remains unchanged*

           ELSE                     ; zeroing-masking

           THEN DEST[31:0] := 0

     FI;

FI;

DEST[127:32] := SRC1[127:32]

DEST[MAXVL-1:128] := 0


MOVSS (Legacy SSE Version When the Source and Destination Operands are Both XMM Registers)
DEST[31:0] := SRC[31:0]
DEST[MAXVL-1:32] (Unmodified)

VMOVSS (VEX.128.F3.0F 11 /r Where the Destination is an XMM Register)
DEST[31:0] := SRC2[31:0]
DEST[127:32] := SRC1[127:32]
DEST[MAXVL-1:128] := 0

VMOVSS (VEX.128.F3.0F 10 /r Where the Source and Destination are XMM Registers)
DEST[31:0] := SRC2[31:0]
DEST[127:32] := SRC1[127:32]
DEST[MAXVL-1:128] := 0

VMOVSS (VEX.128.F3.0F 10 /r When the Source Operand is Memory and the Destination is an XMM Register)
DEST[31:0] := SRC[31:0]
DEST[MAXVL-1:32] := 0

MOVSS/VMOVSS (When the Source Operand is an XMM Register and the Destination is Memory)
DEST[31:0] := SRC[31:0]

MOVSS (Legacy SSE Version when the Source Operand is Memory and the Destination is an XMM Register)
DEST[31:0] := SRC[31:0]
DEST[127:32] := 0
DEST[MAXVL-1:128] (Unmodified)

Intel C/C++ compiler intrinsics#

VMOVSS __m128 _mm_mask_load_ss(__m128 s, __mmask8 k, float * p);
VMOVSS __m128 _mm_maskz_load_ss( __mmask8 k, float * p);
VMOVSS __m128 _mm_mask_move_ss(__m128 sh, __mmask8 k, __m128 sl, __m128 a);
VMOVSS __m128 _mm_maskz_move_ss( __mmask8 k, __m128 s, __m128 a);
VMOVSS void _mm_mask_store_ss(float * p, __mmask8 k, __m128 a);
MOVSS __m128 _mm_load_ss(float * p) MOVSS void_mm_store_ss(float * p, __m128 a) MOVSS __m128 _mm_move_ss(__m128 a, __m128 b);

SIMD Floating-Point Exceptions#

None.

Other Exceptions#

Non-EVEX-encoded instruction, see Table 2-22, "Type 5 Class Exception Conditions," additionally:

#UD               If VEX.vvvv != 1111B.

EVEX-encoded instruction, see Table 2-60, "Type E10 Class Exception Conditions."

Sources

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