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| <title>PMAXSB — Maximum of Packed Signed Byte Integers </title></head> |
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| <h1>PMAXSB — Maximum of Packed Signed Byte Integers</h1> |
| <table> |
| <tr> |
| <th>Opcode/Instruction</th> |
| <th>Op/En</th> |
| <th>64/32 bit Mode Support</th> |
| <th>CPUID Feature Flag</th> |
| <th>Description</th></tr> |
| <tr> |
| <td>66 0F 38 3C /r PMAXSB <em>xmm1, xmm2/m128</em></td> |
| <td>RM</td> |
| <td>V/V</td> |
| <td>SSE4_1</td> |
| <td>Compare packed signed byte integers in <em>xmm1</em> and <em>xmm2/m128</em> and store packed maximum values in <em>xmm1</em>.</td></tr> |
| <tr> |
| <td>VEX.NDS.128.66.0F38.WIG 3C /r VPMAXSB <em>xmm1, xmm2, xmm3/m128</em></td> |
| <td>RVM</td> |
| <td>V/V</td> |
| <td>AVX</td> |
| <td>Compare packed signed byte integers in <em>xmm2</em> and <em>xmm3/m128</em> and store packed maximum values in <em>xmm1</em>.</td></tr> |
| <tr> |
| <td>VEX.NDS.256.66.0F38.WIG 3C /r VPMAXSB <em>ymm1, ymm2, ymm3/m256</em></td> |
| <td>RVM</td> |
| <td>V/V</td> |
| <td>AVX2</td> |
| <td>Compare packed signed byte integers in <em>ymm2</em> and <em>ymm3/m128</em> and store packed maximum values in <em>ymm1</em>.</td></tr></table> |
| <h3>Instruction Operand Encoding</h3> |
| <table> |
| <tr> |
| <td>Op/En</td> |
| <td>Operand 1</td> |
| <td>Operand 2</td> |
| <td>Operand 3</td> |
| <td>Operand 4</td></tr> |
| <tr> |
| <td>RM</td> |
| <td>ModRM:reg (r, w)</td> |
| <td>ModRM:r/m (r)</td> |
| <td>NA</td> |
| <td>NA</td></tr> |
| <tr> |
| <td>RVM</td> |
| <td>ModRM:reg (w)</td> |
| <td>VEX.vvvv (r)</td> |
| <td>ModRM:r/m (r)</td> |
| <td>NA</td></tr></table> |
| <h2>Description</h2> |
| <p>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.</p> |
| <p>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 destina-tion register remain unchanged.</p> |
| <p>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.</p> |
| <p>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.</p> |
| <p>Note: VEX.L must be 0, otherwise the instruction will #UD.</p> |
| <h2>Operation</h2> |
| <pre>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;</pre> |
| <p><strong>VPMAXSB (VEX.128 encoded version)</strong></p> |
| <pre> 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</pre> |
| <p><strong>VPMAXSB (VEX.256 encoded version)</strong></p> |
| <pre> 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;</pre> |
| <h2>Intel C/C++ Compiler Intrinsic Equivalent</h2> |
| <p>(V)PMAXSB:</p> |
| <p> __m128i _mm_max_epi8 ( __m128i a, __m128i b);</p> |
| <p>VPMAXSB:</p> |
| <p>__m256i _mm256_max_epi8 ( __m256i a, __m256i b);</p> |
| <h2>Flags Affected</h2> |
| <p>None.</p> |
| <h2>SIMD Floating-Point Exceptions</h2> |
| <p>None.</p> |
| <h2>Other Exceptions</h2> |
| <p>See Exceptions Type 4; additionally</p> |
| <table class="exception-table"> |
| <tr> |
| <td>#UD</td> |
| <td>If VEX.L = 1.</td></tr></table></body></html> |