Info Catalog as: Xtensa Jump Relaxation as: Xtensa Relaxation

as: Xtensa Immediate Relaxation

 
 9.54.4.4 Other Immediate Field Relaxation
 .........................................
 
 The assembler normally performs the following other relaxations.  They
DONTPRINTYET  can be disabled by using underscore prefixes (Opcode Names Xtensa
 Opcodes.), the '--no-transform' command-line option (*noteCommand-line
DONTPRINTYET DONTPRINTYET  can be disabled by using underscore prefixes (Opcode Names Xtensa
 Opcodes.), the '--no-transform' command-line option (Command-line

 Options Xtensa Options.), or the 'no-transform' directive (*noteDONTPRINTYET DONTPRINTYET  can be disabled by using underscore prefixes (Opcode Names Xtensa
 Opcodes.), the '--no-transform' command-line option (Command-line

 Options Xtensa Options.), or the 'no-transform' directive (
 transform Transform Directive.).
 
    The 'MOVI' machine instruction can only materialize values in the
 range from -2048 to 2047.  Values outside this range are best
 materialized with 'L32R' instructions.  Thus:
 
          movi a0, 100000
 
    is assembled into the following machine code:
 
          .literal .L1, 100000
          l32r a0, .L1
 
    The 'L8UI' machine instruction can only be used with immediate
 offsets in the range from 0 to 255.  The 'L16SI' and 'L16UI' machine
 instructions can only be used with offsets from 0 to 510.  The 'L32I'
 machine instruction can only be used with offsets from 0 to 1020.  A
 load offset outside these ranges can be materialized with an 'L32R'
 instruction if the destination register of the load is different than
 the source address register.  For example:
 
          l32i a1, a0, 2040
 
    is translated to:
 
          .literal .L1, 2040
          l32r a1, .L1
          add a1, a0, a1
          l32i a1, a1, 0
 
 If the load destination and source address register are the same, an
 out-of-range offset causes an error.
 
    The Xtensa 'ADDI' instruction only allows immediate operands in the
 range from -128 to 127.  There are a number of alternate instruction
 sequences for the 'ADDI' operation.  First, if the immediate is 0, the
 'ADDI' will be turned into a 'MOV.N' instruction (or the equivalent 'OR'
 instruction if the code density option is not available).  If the 'ADDI'
 immediate is outside of the range -128 to 127, but inside the range
 -32896 to 32639, an 'ADDMI' instruction or 'ADDMI'/'ADDI' sequence will
 be used.  Finally, if the immediate is outside of this range and a free
 register is available, an 'L32R'/'ADD' sequence will be used with a
 literal allocated from the literal pool.
 
    For example:
 
          addi    a5, a6, 0
          addi    a5, a6, 512
          addi    a5, a6, 513
          addi    a5, a6, 50000
 
    is assembled into the following:
 
          .literal .L1, 50000
          mov.n   a5, a6
          addmi   a5, a6, 0x200
          addmi   a5, a6, 0x200
          addi    a5, a5, 1
          l32r    a5, .L1
          add     a5, a6, a5
 

Info Catalog as: Xtensa Jump Relaxation as: Xtensa Relaxation