Performance Pragma - 10 - 2025.2 English - UG1448

Vitis HLS Messaging (UG1448)

Document ID
UG1448
Release Date
2025-11-20
Version
2025.2 English

Description

Warning: May not meet performance target_ti=1 cycles for loop 'lz4_decompressr' in function 'xf::compression::lz4Decompress' because required loop unroll will likely cause design size to be too large for C-Synthesis to complete. Please relax the target or constrain the loop with unroll or pipeline pragmas.

Explanation

The specified or inferred target interval (target_ti) for this loop is too aggressive and requires full unrolling. This significantly increases compiler instruction size and leads to excessive synthesis time. To complete compilation, the tool will ignore this target_ti.

Recommendation

Either relax the target_ti value to make it less aggressive, or use explicit HLS pragmas such as #pragma HLS pipeline or #pragma HLS unroll to control loop optimization.