pto.plt_b32

pto.plt_b32 is part of the Predicate Generation And Algebra instruction set.

Summary

Generate a 32-bit tail predicate from a runtime element count and update the scalar through a post-update reference.

Mechanism

The installed 3510 Bisheng CCE header exposes plt_b32 as vector_bool plt_b32(uint32_t &scalar, __cce_simd::POST_UPDATE). The call returns a predicate mask and writes the updated scalar value back through the reference argument.

In practice, this is the public CCE helper used for remainder-mask generation: the returned mask enables the currently active lanes, and the scalar reference carries the post-update state into the next step.

Syntax

PTO Assembly Form

%mask, %scalar_out = pto.plt_b32 %scalar_in {post_update} : i32 -> !pto.mask<b32>, i32

AS Level 1 (SSA)

%mask, %scalar_out = pto.plt_b32 %scalar_in {post_update} : i32 -> !pto.mask<b32>, i32

AS Level 2 (DPS)

pto.plt_b32 ins(%scalar_in : i32) outs(%mask, %scalar_out : !pto.mask<b32>, i32)

C++ Intrinsic

uint32_t scalar = elementCount;
vector_bool mask = plt_b32(scalar, __cce_simd::POST_UPDATE);

Inputs

Operand Type Description
%scalar_in i32 Runtime element count carried into the predicate generator
post_update attribute Indicates the public CCE post-update form that writes scalar_out back through the reference

Expected Outputs

Result Type Description
%mask !pto.mask<b32> 32-bit predicate generated from the current scalar value
%scalar_out i32 Scalar value after the intrinsic's post-update step

Side Effects

  • The public CCE call updates the scalar reference argument in place.

Constraints

Constraints

  • The installed public CCE surface for plt_b32 uses a uint32_t & scalar plus __cce_simd::POST_UPDATE.
  • Programs that chain multiple plt_b32 calls must thread the updated scalar value forward explicitly.
  • The returned predicate width is fixed by the _b32 suffix.

Exceptions

Exceptions

  • Illegal if the selected target profile does not support the requested predicate width.
  • Illegal if the post-update scalar state is consumed in a way that breaks the required chaining discipline.

Target-Profile Restrictions

Target-Profile Restrictions
Aspect CPU Sim A2/A3 A5
Tail-predicate helper Simulated Supported Supported
Public post-update scalar form Emulated Supported Supported

Examples

C++ usage

uint32_t scalar = elementCount;
vector_bool mask = plt_b32(scalar, __cce_simd::POST_UPDATE);

SSA form

%mask, %scalar_out = pto.plt_b32 %scalar_in {post_update} : i32 -> !pto.mask<b32>, i32