Instruction Syntax

Mnemonic	Format	Flags
frsp	frD,frB	Rc = 0
frsp.	frD,frB	Rc = 1

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	111111 (0x3F)
frD	6-10	Destination floating-point register
Reserved	11-15	00000
frB	16-20	Source floating-point register B
Reserved	21	0
XO	22-30	000001100 (12)
Rc	31	Record Condition Register

Operation

frD ← SINGLE(frB)

The contents of floating-point register frB are rounded to single-precision using the current rounding mode specified by FPSCR[RN], and the result is placed into floating-point register frD. The result is stored in double-precision format.

Note: This instruction explicitly rounds a double-precision value to single-precision accuracy. It's essential for maintaining precision consistency when mixing single and double-precision operations. The result maintains the IEEE-754 single-precision range and precision but is stored in the double-precision format of the FPR.

Affected Registers

Condition Register (CR1 field)

(if Rc = 1)

• Reflects floating-point exception summary and status

Floating-Point Status and Control Register (FPSCR)

Affected fields:

• FPRF (Floating-Point Result Flags)
• FX (Floating-Point Exception Summary)
• OX (Overflow Exception)
• UX (Underflow Exception)
• XX (Inexact Exception)
• FR (Fraction Rounded)
• FI (Fraction Inexact)

For more information on floating-point status see Section 2.1.4, "Floating-Point Status and Control Register (FPSCR)," in the PowerPC Microprocessor Family: The Programming Environments manual.

Examples

Basic Single-Precision Rounding

lfd f1, double_value(r0)   # Load double-precision value
frsp f2, f1                 # Round to single-precision
stfs f2, single_result(r0)  # Store as single-precision

Mixed-Precision Calculation Chain

# Perform high-precision calculation, then round for storage
lfd f1, input_a(r0)         # Load double-precision input A
lfd f2, input_b(r0)         # Load double-precision input B
fadd f3, f1, f2             # High-precision addition
fmul f4, f3, f1             # High-precision multiplication
frsp f5, f4                 # Round final result to single-precision
stfs f5, result(r0)         # Store single-precision result

Graphics Pipeline: Precision Management

# Convert high-precision vertex calculation to single-precision for GPU
lfd f1, world_matrix_calc(r0) # Load high-precision transformation result
frsp f2, f1                 # Round to single-precision for GPU compatibility
stfs f2, vertex_buffer(r0)  # Store in vertex buffer for graphics hardware

Audio Processing: Sample Rate Conversion

# Convert high-precision audio processing to single-precision output
lfd f1, processed_sample(r0) # Load high-precision processed sample
frsp f2, f1                 # Round to single-precision
stfs f2, audio_output(r0)   # Store single-precision audio sample

Scientific Computing: Precision Control

# Control precision in iterative algorithm
lfd f1, iteration_result(r0) # Load double-precision iteration result
frsp f2, f1                 # Round to single-precision for next iteration
fadd f3, f2, f2             # Continue with single-precision accuracy
stfs f3, next_iteration(r0) # Store for next iteration

Game Engine: Physics to Rendering Pipeline

# Convert physics calculation to rendering precision
lfd f1, physics_position(r0) # Load high-precision physics position
lfd f2, physics_velocity(r0) # Load high-precision velocity
fadd f3, f1, f2             # High-precision position update
frsp f4, f3                 # Round to single-precision for rendering
stfs f4, render_position(r0) # Store rendering position

Network Protocol: Data Precision Standardization

# Standardize floating-point data for network transmission
lfd f1, local_calculation(r0) # Load local high-precision calculation
frsp f2, f1                 # Round to single-precision for network consistency
stfs f2, network_packet(r0) # Store in network packet (single-precision)

Machine Learning: Model Inference Optimization

# Convert training precision to inference precision
lfd f1, training_weight(r0) # Load high-precision training weight
frsp f2, f1                 # Round to single-precision for faster inference
stfs f2, inference_model(r0) # Store optimized inference weight

Financial Computing: Regulatory Compliance

# Round calculation to required precision for reporting
lfd f1, high_precision_calc(r0) # Load high-precision financial calculation
frsp f2, f1                 # Round to single-precision for regulatory reporting
stfs f2, compliance_report(r0) # Store compliant precision result

Real-Time System: Performance Optimization

# Optimize real-time calculation performance
lfd f1, precise_calculation(r0) # Load precise calculation result
frsp f2, f1                 # Round to single-precision for speed
fmuls f3, f2, f2            # Continue with faster single-precision operations
stfs f3, realtime_output(r0) # Store optimized result

Data Analysis: Storage Optimization

# Compress data precision for storage efficiency
lfd f1, analysis_result(r0) # Load analysis result
frsp f2, f1                 # Round to single-precision to save storage
stfs f2, compressed_data(r0) # Store space-efficient data

Embedded System: Memory Conservation

# Convert to single-precision for memory-constrained environment
lfd f1, sensor_reading(r0)  # Load high-precision sensor reading
frsp f2, f1                 # Round to single-precision for embedded storage
stfs f2, embedded_memory(r0) # Store in limited memory system

Related Instructions

fadds, fmuls, fsubs, fdivs, lfs, stfs