What is the main difference from the M form?
The ordinary form returns the other non-NaN operand when exactly one input is NaN; the M form returns canonical NaN if either input is NaN.
FMIN.S
RISC-V FMIN.S Instruction Details
Instruction ManualR-typeReturn the minimum of two single-precision floating-point operands.
Instruction Syntax
fmin.s rd, rs1, rs2
Operand Breakdown
rd: destination floating-point register receiving the formatted result.
rs1/rs2: source floating-point registers; arithmetic/rounding forms with rm use rm or dynamic frm for rounding mode.
FFloating-Point Arithmetic
Instruction Behavior
FMIN.S returns the numerically smaller of two single-precision floating-point operands. If only one operand is NaN, it returns the non-NaN operand; if both are NaN, it returns canonical NaN. A signaling NaN sets NV, and -0.0 is less than +0.0.
Quick Understanding & Search Notes
FMIN.S's key search point is NaN handling. The ordinary form selects the non-NaN operand for a single NaN and returns canonical NaN only when both inputs are NaN.
-0.0 and +0.0 are ordered: -0.0 is less than +0.0.
The instruction does not use rm; it is a selection operation, not rounded arithmetic.
Common Usage Scenarios
Floating-Point Compare
Understand this scenario with real code like «fmin.s f0, f1, f2 # f0 = min(f1,f2)».
Numerical Computing
Understand this scenario with real code like «fmin.s f0, f1, f2 # f0 = min(f1,f2)».
Pre-Use Checklist
Syntax Check
- Confirm the current instruction format is R-type.
- Confirm the operand order matches the example.
Semantic Check
- Ensure the destination register usage is compatible with the calling convention.
- Confirm this is not the lower-level form of a pseudo-instruction expansion.
Pitfalls / Common Confusions
Ordinary FMIN/FMAX returns the non-NaN operand when exactly one input is NaN.
A signaling NaN sets NV; quiet-NaN handling differs between ordinary and M forms.
-0.0 is considered less than +0.0.
FAQ
Does FMIN.S round?
No. It selects between two operands and has no rm rounding field.