1.19.1. Advanced Synthesis Settings

Quartus® Prime Pro Edition User Guide: Design Compilation

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Date 9/30/2024

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1.19.1. Advanced Synthesis Settings

The following section is a quick reference of all Advanced Synthesis Settings. Click Assignments > Settings > Compiler Settings > Advanced Settings (Synthesis) to modify these settings.

Table 38. Advanced Synthesis Settings (1 of 13)
Option	Description
Allow Any RAM Size for Recognition	Allows the Compiler to infer RAMs of any size, even if the RAMs do not meet the current minimum requirements.
Allow Any ROM Size for Recognition	Allows the Compiler to infer ROMs of any size even if the ROMs do not meet the design's current minimum size requirements.
Allow Any Shift Register Size for Recognition	Allows the Compiler to infer shift registers of any size even if they do not meet the design's current minimum size requirements.
Allow Register Duplication	Controls whether the Compiler duplicates registers to improve design performance. When enabled, the Compiler performs optimization that creates a second copy of a register and move a portion of its fan-out to this new node. This technique improves routability and reduces the total routing wire required to route a net with many fan-outs. If you disable this option, retiming of registers is also disabled. Note: Only available for Arria® 10 and Cyclone® 10 GX devices.
Allow Register Merging	Controls whether the Compiler removes (merges) identical registers. When enabled, in cases where two registers generate the same logic, the Compiler may delete one register and fan-out the remaining register to the deleted register's destinations. This option is useful if you want to prevent the Compiler from removing duplicate registers that you have used deliberately. When disabled, retiming optimizations are also disabled. Note: Only available for Arria® 10 and Cyclone® 10 GX devices.
Allow Shift Register Merging Across Hierarchies	Allows the Compiler to take shift registers from different hierarchies of the design and put the registers in the same RAM.
Allow Synchronous Control Signals	Allows the Compiler to utilize synchronous clear and synchronous load signals in normal mode logic cells. Turning on this option helps to reduce the total number of logic cells used in the design, but can negatively impact the fitting. This negative impact occurs because all the logic cells in a LAB share synchronous control signals.

Table 39. Advanced Synthesis Settings (2 of 13)
Option	Description
Analysis & Synthesis Message Level	Specifies the type of Analysis & Synthesis messages the Compiler display. Low displays only the most important Analysis & Synthesis messages. Medium displays most messages, but hides the detailed messages. High displays all messages.
Auto Clock Enable Replacement	Allows the Compiler to locate logic that feeds a register and move the logic to the register's clock enable input port.
Auto DSP Block Replacement	Allows the Compiler to find a multiply-accumulate function or a multiply-add function that can be replaced with a DSP block.
Auto Gated Clock Conversion	Automatically converts gated clocks to use clock enable pins. Clock gating logic can contain AND, OR, MUX, and NOT gates. Turning on this option may increase memory use and overall run time. You must use the Timing Analyzer for timing analysis, and you must define all base clocks in Synopsys Design Constraints (.sdc) format.

Table 40. Advanced Synthesis Settings (3 of 13)
Option	Description
Auto Open-Drain Pins	Allows the Compiler to automatically convert a tri-state buffer with a strong low data input into the equivalent open-drain buffer.
Auto RAM Replacement	Allows the Compiler to identify sets of registers and logic that it can replace with the altsyncram or the lpm_ram_dp IP core. Turning on this option may change the functionality of the design.
Auto ROM Replacement	Allows the Compiler to identify logic that it can replace with the altsyncram or the lpm_rom IP core. Turning on this option may change the power-up state of the design.
Auto Resource Sharing	Allows the Compiler to share hardware resources among many similar, but mutually exclusive, operations in your HDL source code. If you enable this option, the Compiler merges compatible addition, subtraction, and multiplication operations. Merging operations may reduce the area your design requires. Because resource sharing introduces extra muxing and control logic on each shared resource, it may negatively impact the final f_MAX of your design.
Auto Shift Register Placement	Allows the Compiler to find a group of shift registers of the same length that are replaceable with the altshift_taps IP core. The shift registers must all use the same clock and clock enable signals. The registers must not have any other secondary signals. The registers must have equally spaced taps that are at least three registers apart.
Automatic Parallel Synthesis	Option to enable/disable automatic parallel synthesis. Use this option to speed up synthesis compile time by using multiple processors when available.

Table 41. Advanced Synthesis Settings (4 of 13)
Option	Description
Block Design Naming	Specifies the naming scheme for the block design. The Compiler ignores the option if you assign the option to anything other than a design entity.
Clock MUX Protection	Causes the multiplexers in the clock network to decompose to 2-to-1 multiplexer trees. The Compiler protects these trees from merging with, or transferring to, other logic. This option helps the Timing Analyzer to analyze clock behavior.
DSP Block Balancing	Allows you to control the conversion of certain DSP block slices during DSP block balancing.

Table 42. Advanced Synthesis Settings (5 of 13)
Option	Description
Disable DSP Negate Inferencing	Allows you to specify whether to use the negate port on an inferred DSP block.
Disable Register Merging Across Hierarchies	Specifies whether the Compiler allows merging of registers that are in different hierarchies if their inputs are the same.
Enable Formal Verification Support	Enables the Compiler to write scripts for use with the OneSpin* formal verification tool.
Enable State Machines Inference	Allows the Compiler to infer state machines from VHDL or Verilog HDL design files. The Compiler optimizes state machines to reduce area and improve performance. If set to Off, the Compiler extracts and optimizes state machines in VHDL or Verilog HDL design files as regular logic.
Enable SystemVerilog static assertion support	Enables immediate assertions in the Compiler for information, warning, and error messages for SystemVerilog designs.
Enable VHDL static assertion support	Enables immediate assertions in the Compiler for information, warning, and error messages for VHDL designs.
Force Use of Synchronous Clear Signals	Forces the Compiler to utilize synchronous clear signals in normal mode logic cells. Enabling this option helps to reduce the total number of logic cells in the design, but can negatively impact the fitting. All the logic cells in a LAB share synchronous control signals.
Fractal Synthesis	Turning this option On directs the Compiler to apply dense packing to arithmetic blocks, minimizing the area of the design for arithmetic-intensive designs.
HDL Message Level	Specifies the type of HDL messages you want to view, including messages that display processing errors in the HDL source code. Level1 displays only the most important HDL messages. Level2 displays most HDL messages, including warning and information based messages. Level3 displays all HDL messages, including warning and information based messages and alerts about potential design problems or lint errors.

Table 43. Advanced Synthesis Settings (6 of 13)
Option	Description
Ignore GLOBAL Buffers	Ignores `GLOBAL` buffers in the design. The Compiler ignores this option if you apply the option to anything other than an individual `GLOBAL` buffer, or a design entity containing `GLOBAL` buffers.
Ignore LCELL Buffers	Ignores `LCELL` buffers in the design. The Compiler ignores this option if you apply the option to anything other than an individual `LCELL` buffer, or a design entity containing `LCELL` buffers.
Ignore Maximum Fan-Out Assignments	Directs the Compiler to ignore the Maximum Fan-Out Assignments on a node, an entity, or the whole design.
Ignore SOFT Buffers	Ignores `SOFT` buffers in the design. The Compiler ignores this option if you apply the option to anything other than an individual `SOFT` buffer or a design entity containing SOFT buffers.

Table 44. Advanced Synthesis Settings (7 of 13)
Option	Description
Ignore translate_off and synthesis_off Directives	Ignores all `translate_off/synthesis_off` synthesis directives in Verilog HDL and VHDL design files. Use this option to disable these synthesis directives and include previously ignored code during elaboration.
Infer RAMs from Raw Logic	Infers RAM from registers and multiplexers. The Compiler initially converts some HDL patterns differing from RAM templates into logic. However, these structures function as RAM. As a result, when you enable this option, the Compiler may substitute the altsyncram IP core instance for them at a later stage. When you enable this assignment, the Compiler may use more device RAM resources and fewer LABs.
Iteration Limit for Constant Verilog Loops	Defines the iteration limit for Verilog loops with loop conditions that evaluate to compile-time constants on each loop iteration. This limit exists primarily to identify potential infinite loops before they exhaust memory or trap the software in an actual infinite loop.
Iteration Limit for non-Constant Verilog Loops	Defines the iteration limit for Verilog HDL loops with loop conditions that do not evaluate to compile-time constants on each loop iteration. This limit exists primarily to identify potential infinite loops before they exhaust memory or trap the software in an actual infinite loop.

Table 45. Advanced Synthesis Settings (8 of 13)
Option	Description
Maximum DSP Block Usage	Specifies the maximum number of DSP blocks that the DSP block balancer assumes exist in the current device for each partition. This option overrides the usual method of using the maximum number of DSP blocks the current device supports.
Maximum Number of LABs	Specifies the maximum number of LABs that Analysis & Synthesis should try to utilize for a device. This option overrides the usual method of using the maximum number of LABs the current device supports, when the value is non-negative and is less than the maximum number of LABs available on the current device.
Maximum Number of M4K/M9K/M20K/M10K Memory Blocks	Specifies the maximum number of M4K, M9K, M20K, or M10K memory blocks that the Compiler may use for a device. This option overrides the usual method of using the maximum number of M4K, M9K, M20K, or M10K memory blocks the current device supports, when the value is non-negative and is less than the maximum number of M4K, M9K, M20K, or M10K memory blocks available on the current device.

Table 46. Advanced Synthesis Settings (9 of 13)
Option	Description
Maximum Number of Registers Created from Uninferred RAMs	Specifies the maximum number of registers that Analysis & Synthesis uses for conversion of uninferred RAMs. Use this option as a project-wide option or on a specific partition by setting the assignment on the instance name of the partition root. The assignment on a partition overrides the global assignment (if any) for that particular partition. This option prevents synthesis from causing long compilations and running out of memory when many registers are used for uninferred RAMs. Instead of continuing the compilation, the Quartus® Prime software issues an error and exits.
NOT Gate Push-Back	Allows the Compiler to push an inversion (that is, a NOT gate) back through a register and implement it on that register's data input if it is necessary to implement the design. When this option is on, a register may power-up to an active-high state, and may need explicit clear during initial operation of the device. The Compiler ignores this option if you apply it to anything other than an individual register or a design entity containing registers. When you apply this option to an output pin that is directly fed by a register, the assignment automatically transfers to that register.
Number of Inverted Registers Reported in Synthesis Report	Specifies the maximum number of inverted registers that the Synthesis report displays.
Number of Protected Registers Reported in Synthesis Report	Specifies the maximum number of protected registers that the Synthesis Report displays.
Number of Removed Registers Reported in Synthesis Migration Checks	Specifies the maximum number of rows that the Synthesis Migration Check report displays.
Number of Swept Nodes Reported in Synthesis Report	Specifies the maximum number of swept nodes that the Synthesis Report displays. A swept node is any node which was eliminated from your design because the Compiler found the node to be unnecessary.
Number of Rows Reported in Synthesis Report	Specifies the maximum number of rows that the Synthesis report displays. Note: Only available for Arria® 10 and Cyclone® 10 GX devices.
Optimization Technique	Specifies an overall optimization goal for Analysis & Synthesis. Specify a Balanced strategy, or optimize for Performance, Area, Routability, Power, or Compile Time. The Compiler targets the optimization goal you specify.

Table 47. Advanced Synthesis Settings (10 of 13)
Option	Description
Perform WYSIWYG Primitive Resynthesis	Specifies whether to perform WYSIWYG primitive resynthesis during synthesis. This option uses the setting specified in the Optimization Technique logic option.
Power-Up Don't Care	Causes registers that do not have a Power-Up Level logic option setting to power-up with a do not care logic level (`X`). When the Power-Up Don't Care option is on, the Compiler determines when it is beneficial to change the power-up level of a register to minimize the area of the design. The Compiler maintains a power-up state of zero, unless there is an immediate area advantage.
Power Optimization During Synthesis	Controls the power-driven compilation setting of Analysis & Synthesis. This option determines how aggressively Analysis & Synthesis optimizes the design for power. When this option is Off, the Compiler does not perform any power optimizations. Normal compilation performs power optimizations provided that they are not expected to reduce design performance. Extra effort performs additional power optimizations which may reduce design performance.

Table 48. Advanced Synthesis Settings (11 of 13)
Option	Description
Remove Duplicate Registers	Removes a register if it is identical to another register. If two registers generate the same logic, the Compiler deletes the duplicate. The first instance fans-out to the duplicates destinations. Also, if the deleted register contains different logic option assignments, the Compiler ignores the options. This option is useful if you want to prevent the Compiler from removing intentionally duplicate registers. The Compiler ignores this option if you apply it to anything other than an individual register or a design entity containing registers.
Remove Redundant Logic Cells	Removes redundant LCELL primitives or WYSIWYG primitives. Turning this option on optimizes a circuit for area and speed. The Compiler ignores this option if you apply it to anything other than a design entity.
Report Parameter Settings	Specifies whether the Synthesis report includes the reports in the Parameter Settings by Entity Instance folder.
Report PR Initial Values as Errors	Allows you to flag explicitly defined initial values found in PR partitions as Errors instead of Warnings.
Report Source Assignments	Specifies whether the Synthesis report includes reports in the Source Assignments folder.

Table 49. Advanced Synthesis Settings (12 of 13)
Option	Description
Resource Aware Inference for Block RAM	Specifies whether RAM, ROM, and shift-register inference should take the design and device resources into account.
Restructure Multiplexers	Reduces the number of logic elements synthesis requires to implement multiplexers in a design. This option is useful if your design contains buses of fragmented multiplexers. This option repacks multiplexers more efficiently for area, allowing the design to implement multiplexers with a reduced number of logic elements: On—minimizes your design area, but may negatively affect design clock speed (f_MAX). Off—disables multiplexer restructuring; it does not decrease logic element usage and does not affect design clock speed (f_MAX). Auto—allows the Quartus® Prime software to determine whether multiplexer restructuring should be enabled. The Auto setting decreases logic element usage, but may negatively affect design clock speed (f_MAX).
SDC Constraint Protection	Verifies.sdc constraints in register merging. This option helps to maintain the validity of .sdc constraints through compilation.
Safe State Machine	The Safe State Machine option implements state machines that can recover from an illegal state. The following settings are available: Auto—for Stratix® 10 or Agilex™ family designs, this default setting enables Safe State Machine whenever the Compiler determines this setting is advantageous in state machines of 6 or less states. The setting helps to allow for unexpected initial power-up conditions. For Arria® 10 and Cyclone® 10 GX, the Auto setting is the same as Never. On—directs the Compiler to always use Safe State Machine. Never—never uses Safe State Machine.
Shift Register Replacement – Allow Asynchronous Clear Signal	Allows the Compiler to find a group of shift registers of the same length that can be replaced with the altshift_taps IP core. The shift registers must all use the same `aclr` signals, must not have any other secondary signals, and must have equally spaced taps that are at least three registers apart. To use this option, you must turn on the Auto Shift Register Replacement logic option.
Size of the Latch Report	Allows you to specify the maximum number of latches that the Synthesis Report should display.
Size of the PR Initial Conditions Report	Allows you to specify the maximum number of registers that the PR Initial Conditions Report should display.

Table 50. Advanced Synthesis Settings (13 of 13)
Option	Description
State Machine Processing	Specifies the processing style the Compiler uses to process a state machine. You can use your own User-Encoded style, or select One-Hot, Minimal Bits, Gray, Johnson, Sequential, or Auto (Compiler-selected) encoding.
Strict RAM Replacement	When this option is On, the Compiler replace RAM only if the hardware matches the design exactly.
Synchronization Register Chain Length	Specifies the maximum number of registers in a row that the Compiler considers as a synchronization chain. Synchronization chains are sequences of registers with the same clock and no fan-out in between, such that the first register is fed by a pin, or by logic in another clock domain. The Compiler considers these registers for metastability analysis. The Compiler prevents optimizations of these registers, such as retiming. When gate-level retiming is enabled, the Compiler does not remove these registers. The default length is set to two.
Synthesis Effort	Controls the synthesis trade-off between compilation speed, performance, and area. The default is Auto. You can select Fast for faster compilation speed at the cost of performance and area.
Synthesis Migration Check for Stratix 10	Enables synthesis checks on Arria® 10 to Stratix® 10 design migration.
Timing-Driven Synthesis	For Arria® 10 and Cyclone® 10 GX designs, allows synthesis to use timing information to better optimize the design. The Timing-Driven Synthesis logic option impacts the following Optimization Technique options: Optimization Technique Speed—optimizes timing-critical portions of your design for performance at the cost of increasing area (logic and register utilization) Optimization Technique Balanced—also optimizes the timing-critical portions of your design for performance, but the option allows only limited area increase Optimization Technique Area—optimizes your design only for area