v_msad_u8 GPU Native ISA AMD Vector

V MSAD U8 Vector Arithmetic

v_msad_u8

Calculate the sum of absolute differences of elements in two packed 4-component unsigned 8-bit integer inputs, except that elements where the second…

Encoding

Verified bit-level encoding data is not yet available for this instruction. The instruction-format classification below (VOP3) is well-documented and stable; exact per-target opcode/field bit positions have not yet been imported from a verified source.
Format VOP3
Execution Unit

Operands

Operand details have not yet been curated for this instruction.

GFX Target Compatibility

TargetSupport
gfx1100✅ Supported

Overflow into the upper bits is allowed.

Related

More in Vector Arithmetic

Reference

AMDGPU / GFX ISA

Description

Calculate the sum of absolute differences of elements in two packed 4-component unsigned 8-bit integer inputs, except that elements where the second input (known as the reference input) is zero are not included in the sum. Add an unsigned 32-bit integer value from the third input and store the result into a vector register.

Semantics

ABSDIFF = lambda(x, y) ( x > y ? x - y : y - x); // UNSIGNED comparison tmp = S2.u32; tmp += S1.u32[7 : 0] == 8'0U ? 0U : 32'U(ABSDIFF(S0.u32[7 : 0], S1.u32[7 : 0])); tmp += S1.u32[15 : 8] == 8'0U ? 0U : 32'U(ABSDIFF(S0.u32[15 : 8], S1.u32[15 : 8])); tmp += S1.u32[23 : 16] == 8'0U ? 0U : 32'U(ABSDIFF(S0.u32[23 : 16], S1.u32[23 : 16])); tmp += S1.u32[31 : 24] == 8'0U ? 0U : 32'U(ABSDIFF(S0.u32[31 : 24], S1.u32[31 : 24])); D0.u32 = tmp

Example

v_msad_u8 v5, v1, v2, s3

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx11). Not from an AMD document, and not authored here.

Sources