PMAXSB — Maximum of Packed Signed Byte Integers

Instruction Operand Encoding

Description

Compares packed signed byte integers in the destination operand (first operand) and the source operand (second operand), and returns the maximum for each packed value in the destination operand. 128-bit Legacy SSE version: The first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (VLMAX-1:128) of the corresponding YMM destination register remain unchanged. VEX.128 encoded version: The first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (VLMAX-1:128) of the destination YMM register are zeroed. VEX.256 encoded version: The second source operand can be an YMM register or a 256-bit memory location. The first source and destination operands are YMM registers.

Note: VEX.L must be 0, otherwise the instruction will #UD.

Operation

IF (DEST[7:0] > SRC[7:0])
  THEN DEST[7:0] ← DEST[7:0];
  ELSE DEST[7:0] ← SRC[7:0]; FI;
IF (DEST[15:8] > SRC[15:8])
  THEN DEST[15:8] ← DEST[15:8];
  ELSE DEST[15:8] ← SRC[15:8]; FI;
IF (DEST[23:16] > SRC[23:16])
  THEN DEST[23:16] ← DEST[23:16];
  ELSE DEST[23:16] ← SRC[23:16]; FI;
IF (DEST[31:24] > SRC[31:24])
  THEN DEST[31:24] ← DEST[31:24];
  ELSE DEST[31:24] ← SRC[31:24]; FI;
IF (DEST[39:32] > SRC[39:32])
  THEN DEST[39:32] ← DEST[39:32];
  ELSE DEST[39:32] ← SRC[39:32]; FI;
IF (DEST[47:40] > SRC[47:40])
  THEN DEST[47:40] ← DEST[47:40];
  ELSE DEST[47:40] ← SRC[47:40]; FI;
IF (DEST[55:48] > SRC[55:48])
  THEN DEST[55:48] ← DEST[55:48];
  ELSE DEST[55:48] ← SRC[55:48]; FI;
IF (DEST[63:56] > SRC[63:56])
  THEN DEST[63:56] ← DEST[63:56];
  ELSE DEST[63:56] ← SRC[63:56]; FI;
IF (DEST[71:64] > SRC[71:64])
  THEN DEST[71:64] ← DEST[71:64];
  ELSE DEST[71:64] ← SRC[71:64]; FI;
IF (DEST[79:72] > SRC[79:72])
  THEN DEST[79:72] ← DEST[79:72];
  ELSE DEST[79:72] ← SRC[79:72]; FI;
IF (DEST[87:80] > SRC[87:80])
  THEN DEST[87:80] ← DEST[87:80];
  ELSE DEST[87:80] ← SRC[87:80]; FI;
IF (DEST[95:88] > SRC[95:88])
  THEN DEST[95:88] ← DEST[95:88];
  ELSE DEST[95:88] ← SRC[95:88]; FI;
IF (DEST[103:96] > SRC[103:96])
  THEN DEST[103:96] ← DEST[103:96];
  ELSE DEST[103:96] ← SRC[103:96]; FI;
IF (DEST[111:104] > SRC[111:104])
  THEN DEST[111:104] ← DEST[111:104];
  ELSE DEST[111:104] ← SRC[111:104]; FI;
IF (DEST[119:112] > SRC[119:112])
  THEN DEST[119:112] ← DEST[119:112];
  ELSE DEST[119:112] ← SRC[119:112]; FI;
IF (DEST[127:120] > SRC[127:120])
  THEN DEST[127:120] ← DEST[127:120];
  ELSE DEST[127:120] ← SRC[127:120]; FI;
VPMAXSB (VEX.128 encoded version)
  IF SRC1[7:0] >SRC2[7:0] THEN
     DEST[7:0] ← SRC1[7:0];
  ELSE
     DEST[7:0] ← SRC2[7:0]; FI;
  (* Repeat operation for 2nd through 15th bytes in source and destination operands *)
  IF SRC1[127:120] >SRC2[127:120] THEN
     DEST[127:120] ← SRC1[127:120];
  ELSE
     DEST[127:120] ← SRC2[127:120]; FI;
DEST[VLMAX-1:128] ← 0
VPMAXSB (VEX.256 encoded version)
  IF SRC1[7:0] >SRC2[7:0] THEN
     DEST[7:0] ← SRC1[7:0];
  ELSE
     DEST[15:0] ← SRC2[7:0]; FI;
  (* Repeat operation for 2nd through 31st bytes in source and destination operands *)
  IF SRC1[255:248] >SRC2[255:248] THEN
     DEST[255:248] ← SRC1[255:248];
  ELSE
     DEST[255:248] ← SRC2[255:248]; FI;

Intel C/C++ Compiler Intrinsic Equivalent

Flags Affected

None.

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Exceptions Type 4; additionally