fmax

Floating-Point Maximum (Scalar)

FMAX <Hd|Sd|Dd>, <Hn|Sn|Dn>, <Hm|Sm|Dm>

Returns the larger of two values.

Pseudocode Operation

if HaveFPExt() then
  Vd ← FPMax(Vn, Vm)
else
  UNDEFINED

Example

FMAX Dd, Dn, Dm

Encoding

Binary Layout
0
31
0
30
0
29
11110
28:24
00
23:22
1
21
Rm
20:16
01
15:14
00
13:12
10
11:10
Rn
9:5
Rd
4:0
 
Format FP Data Processing
Opcode 0x1E204800
Extension Floating Point

Operands

  • Hd|Sd|Dd
    Destination SIMD&FP register (half, single or double-precision)
  • Hn|Sn|Dn
    First source SIMD&FP register (half, single or double-precision)
  • Hm|Sm|Dm
    Second source SIMD&FP register (half, single or double-precision)

Related

Other forms of fmax

  • fmax Vector Floating-Point Maximum
  • fmax SVE Floating-Point Maximum
  • fmax Floating-Point Maximum (Half-Precision)

More in Floating Point

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding Instruction ISA Bit pattern
0x0E403400 FMAX <Vd>.<T>, <Vn>.<T>, <Vm>.<T> A64 0 | Q | 0 | 01110 | 0 | 10 | Rm | 00 | 110 | 1 | Rn | Rd
0x0E20F400 FMAX <Vd>.<T>, <Vn>.<T>, <Vm>.<T> A64 0 | Q | 0 | 01110 | 0 | sz | 1 | Rm | 11110 | 1 | Rn | Rd
0x1EE04800 FMAX <Hd>, <Hn>, <Hm> A64 0 | 0 | 0 | 11110 | 11 | 1 | Rm | 01 | 00 | 10 | Rn | Rd
0x1E204800 FMAX <Sd>, <Sn>, <Sm> A64 0 | 0 | 0 | 11110 | 00 | 1 | Rm | 01 | 00 | 10 | Rn | Rd
0x1E604800 FMAX <Dd>, <Dn>, <Dm> A64 0 | 0 | 0 | 11110 | 01 | 1 | Rm | 01 | 00 | 10 | Rn | Rd
0xC120A100 FMAX { <Zdn1>.<T>-<Zdn2>.<T> }, { <Zdn1>.<T>-<Zdn2>.<T> }, <Zm>.<T> A64 11000001 | size | 10 | Zm | 101000 | 0100 | 0 | Zdn | 0
0xC120A900 FMAX { <Zdn1>.<T>-<Zdn4>.<T> }, { <Zdn1>.<T>-<Zdn4>.<T> }, <Zm>.<T> A64 11000001 | size | 10 | Zm | 101010 | 0100 | 0 | Zdn | 0 | 0
0xC120B100 FMAX { <Zdn1>.<T>-<Zdn2>.<T> }, { <Zdn1>.<T>-<Zdn2>.<T> }, { <Zm1>.<T>-<Zm2>.<T> } A64 11000001 | size | 1 | Zm | 0101100 | 010 | 0 | 0 | Zdn | 0
0xC120B900 FMAX { <Zdn1>.<T>-<Zdn4>.<T> }, { <Zdn1>.<T>-<Zdn4>.<T> }, { <Zm1>.<T>-<Zm4>.<T> } A64 11000001 | size | 1 | Zm | 00101110 | 010 | 0 | 0 | Zdn | 0 | 0
0x651E8000 FMAX <Zdn>.<T>, <Pg>/M, <Zdn>.<T>, <const> A64 01100101 | size | 011 | 11 | 0 | 100 | Pg | 0000 | i1 | Zdn
0x65068000 FMAX <Zdn>.<T>, <Pg>/M, <Zdn>.<T>, <Zm>.<T> A64 01100101 | size | 00 | 011 | 0 | 100 | Pg | Zm | Zdn

Description

Floating-point Maximum (scalar). This instruction compares the two source SIMD&FP registers, and writes the larger of the two floating-point values to the destination SIMD&FP register. When FPCR.AH is 0, the behavior is as follows: When FPCR.AH is 1, the behavior is as follows: This instruction can generate a floating-point exception. Depending on the settings in FPCR, the exception results in either a flag being set in FPSR, or a synchronous exception being generated. For more information, see Floating-point exception traps. Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Operation

CheckFPEnabled64();
bits(esize) operand1 = V[n, esize];
bits(esize) operand2 = V[m, esize];

boolean merge = IsMerging(FPCR);
bits(128) result = if merge then V[n, 128] else Zeros(128);

Elem[result, 0, esize] = FPMax(operand1, operand2, FPCR);
V[d, 128] = result;