pto.pldi

pto.pldi is part of the Predicate Load Store instruction set.

Summary

Load the full predicate register from a UB location with an immediate (compile-time constant) byte offset.

Mechanism

pto.pldi reads a predicate word from a UB address computed as base + imm * 8, then materializes it as !pto.mask<G>. The offset is a compile-time immediate, enabling address resolution at assembly time.

For predicate width Pw, UB base base, and immediate offset imm:

\[ \mathrm{addr} = base + imm \times 8 $$ $$ \mathrm{mask} = \mathrm{READ\_UB}_{64}(\mathrm{addr}) \]

The immediate offset is encoded directly in the instruction word, in units of 8 bytes (64 bits).

Syntax

PTO Assembly Form

%mask = pto.pldi %ub_ptr, %imm, "DIST" : !pto.ptr<i64, ub>, i32 -> !pto.mask<G>

AS Level 1 (SSA)

%mask = pto.pldi %ub_ptr, %imm, "DIST" : !pto.ptr<i64, ub>, i32 -> !pto.mask<G>

AS Level 2 (DPS)

pto.pldi ins(%ub_ptr, %imm, "DIST" : !pto.ptr<i64, ub>, i32) outs(%mask : !pto.mask<G>)

C++ Intrinsic

vector_bool dst;
__ubuf__ uint32_t *base;
int32_t offset = 0;
pldi(dst, base, offset, __cce_simd::NORM);
pldi(dst, base, offset, __cce_simd::NORM, __cce_simd::POST_UPDATE);

Inputs

Operand Type Description
%ub_ptr !pto.ptr<i64, ub> UB base address
%imm i32 Immediate byte offset in 8-byte units (compile-time constant)
"DIST" string attribute Distribution mode: "NORM", "US", or "DS"

Expected Outputs

Result Type Description
%mask !pto.mask<G> Loaded predicate register

Side Effects

None.

Constraints

Constraints

  • UB address space: %ub_ptr MUST have address space ub.
  • Offset alignment: The effective address MUST be 64-bit aligned. That is, imm * 8 MUST be a multiple of 8. Misaligned effective addresses are illegal.
  • Immediate range: The offset immediate MUST fit in the instruction encoding.具体的立即数范围由目标 Profile 定义；超出范围的值为 illegal。
  • Distribution mode: The dist attribute MUST be one of "NORM", "US", or "DS".
  • Predicate width: The load transfers exactly 64 bits, which MUST match the active element type context.

Exceptions

Exceptions

  • Illegal if %ub_ptr is not a UB-space pointer.
  • Illegal if the effective address is not 64-bit aligned.
  • Illegal if the immediate offset is out of range for the target profile.
  • Illegal if dist attribute is not a supported distribution mode.

Target-Profile Restrictions

Target-Profile Restrictions
Aspect CPU Sim A2/A3 A5
Immediate-offset predicate load Simulated Supported Supported
"NORM" distribution mode Supported Supported Supported
"US" / "DS" distribution modes Simulated Supported Supported
Immediate offset range Implementation-defined 0–255 (8-byte units) 0–1023 (8-byte units)

Examples

Load predicate with immediate offset

#include <pto/pto-inst.hpp>
using namespace pto;

void load_immediate(RegBuf<predicate_t>& dst,
                    Ptr<ub_space_t, ub_t> base) {
    // Load predicate from base + 3 * 8 = base + 24 bytes
    PLDI(dst, base, 3, "NORM");
}

SSA form

// Load predicate from slot 2 (2 * 8 = 16 bytes offset)
%mask = pto.pldi %ub_base, 2, "NORM" : !pto.ptr<i64, ub>, i32 -> !pto.mask<G>

// Use in predicated vector select
%result = pto.vsel %v_true, %v_false, %mask : !pto.vreg<64xf32>, !pto.vreg<64xf32>, !pto.mask<b32> -> !pto.vreg<64xf32>