discard GPU Virtual ISA NVIDIA

discard Data Movement and Conversion Instructions

discard{.global}.level [a], size;

Semantically, this behaves like a weak write of an unstable indeterminate value: reads of memory locations with unstable indeterminate values may return different bit patterns each time until the memory is overwritten.

Encoding

PTX is a virtual instruction set. It has no single, stable native binary encoding - the compiler lowers this instruction to different native machine code depending on the selected NVIDIA target architecture (compute capability). This page intentionally shows no bit-diagram; see the target/version requirements below for what governs how this instruction compiles.
PTX ISA Version Introduced PTX ISA 7.4
Minimum Target sm_80

Syntax Forms

One mnemonic covers many type / state-space / scope / modifier combinations - each row below is an independently valid form.

Syntax Data Types State Space(s) Modifiers Min. Target Description
discard{.global}.level [a], size; sm_80 Semantically, this behaves like a weak write of an unstable indeterminate value: reads of memory locations with unstable indeterminate values may return different bit patterns each time until the memo… (see the official PTX ISA docs for the full description)

Operands

At a Glance

Data Types -

Related

More in Data Movement and Conversion Instructions

Reference

NVIDIA PTX ISA

Description

Semantically, this behaves like a weak write of an unstable indeterminate value: reads of memory locations with unstable indeterminate values may return different bit patterns each time until the memory is overwritten. This operation hints to the implementation that data in the specified cache.level can be destructively discarded without writing it back to memory. The operand size is an integer constant that specifies the length in bytes of the address range [a, a + size) to write unstable indeterminate values into. The only supported value for the size operand is 128. If no state space is specified then Generic Addressing is used. (see the official PTX ISA docs for the full description)

Examples

discard.global.L2 [ptr], 128;
ld.weak.u32 r0, [ptr];
ld.weak.u32 r1, [ptr];
// The values in r0 and r1 may differ!

Reproduced from NVIDIA's official PTX ISA documentation for technical accuracy.

Sources