Is rd a floating-point register for FEQ.Q?
No. rd is an integer register holding the Boolean result 0 or 1.
FEQ.Q
RISC-V FEQ.Q Instruction Details
Instruction ManualR-typequad-precision floating-point equality compare; writes x[rd]=1 when true, otherwise 0.
Instruction Syntax
feq.q rd, rs1, rs2
Operand Breakdown
rd: destination integer register receiving a 0 or 1 comparison result.
rs1/rs2: source floating-point registers; compare instructions do not use an rm rounding mode.
QFloating-Point Compare
Instruction Behavior
FEQ.Q compares the quad-precision floating-point values in f[rs1] and f[rs2] and writes the Boolean result to integer register rd. The encoding uses the OP-FP opcode, funct5=10100, fmt=Q(11), and funct3=010; it is a quiet comparison that sets NV only for signaling NaN, and any NaN operand makes the result 0.
FEQ.Q Decode And Execute Animation
Shows the Q-extension quad-precision OP-FP flow: decode fields, read FP operands, perform FEQ semantics, then write rd.
rd
rs1
rs2
feq.q
,
,
Execution Context
FLEN=128 / fmt=Q (11)
funct3: equality compare
fflags: example fflags remains 0
31..27
26..25
24..20
19..15
14..12
11..7
6..0
10100
FEQ
11
fmt=Q
01100
rs2
01011
rs1
010
funct3=010
01010
rd
1010011
OP-FP
Execution Data Path
instruction
0xA6C5A553
opcode
1010011 -> OP-FP
funct5/fmt
10100 + Q(11) -> FEQ.Q
funct3
010 -> equality compare
rd/rs
a0(x10) / fa1(f11) / fa2(f12)
read
1.5, 1.5
FP op
1.5 == 1.5 -> 1
write
a0(x10) = 1; example fflags remains 0
Current Step
Fetch: show the 32-bit OP-FP encoding
The word is split as an R-type OP-FP instruction; quad-precision OP-FP instructions use opcode 1010011.
encoding: 0xA6C5A553
syntax : feq.q a0(x10), fa1(f11), fa2(f12)
result : a0(x10) = 1; example fflags remains 0
The comparison result is written to integer register x[rd] and is only 0 or 1; compare instructions do not use rm.
Quad-precision Calculation
rs1
fa1(f11) = 1.5
rs2
fa2(f12) = 1.5
result
1.5 == 1.5 -> 1
The comparison result is written to integer register x[rd] and is only 0 or 1; compare instructions do not use rm.
This animation shows only Q-extension ISA-visible OP-FP encoding, example numeric results, and fflags relationship; it does not model FPU pipelines, latency, every IEEE 754 corner case, or microarchitecture.
Quick Understanding & Search Notes
FEQ.Q writes the quad-precision FP comparison result to integer register x[rd]; the result is only 0 or 1.
OP-FP opcode is 1010011; funct5=10100, fmt=11, and funct3=010 select FEQ.Q.
It writes 1 when rs1 == rs2 is true, otherwise 0; any NaN operand writes 0.
FEQ is a quiet comparison: qNaN leaves NV clear, while sNaN sets NV.
The comparison produces no FP result and has no rm rounding field; rd is an integer register.
Common Usage Scenarios
Comparison & Detection
Understand this scenario with real code like «feq.q x10, f0, f1 # x10 = (f0==f1)».
Floating-Point Conditions
Understand this scenario with real code like «feq.q x10, f0, f1 # x10 = (f0==f1)».
Pre-Use Checklist
Syntax Check
- rd: destination integer register receiving a 0 or 1 comparison result.
- rs1/rs2: source floating-point registers; compare instructions do not use an rm rounding mode.
Semantic Check
- Confirm the result is written to an integer register and is only 0 or 1.
- Confirm quiet/signaling comparison behavior for NaNs and NV matches the need.
Pitfalls / Common Confusions
Quiet comparisons set NV only for signaling NaNs; a quiet NaN only makes the result 0.
rd is an integer register and receives 0 or 1, not a floating-point value.
The comparison does not use the rm rounding mode.
FAQ
What happens on NaN operands for FEQ.Q?
Any NaN operand makes the result 0; qNaN leaves NV clear, while sNaN sets NV.
Does FEQ.Q use rm?
No. The funct3 field selects the comparison type, and the result is an integer Boolean.