as: Xtensa Immediate Relaxation
1
1 9.55.4.4 Other Immediate Field Relaxation
1 .........................................
1
1 The assembler normally performs the following other relaxations. They
DONTPRINTYET 11 can be disabled by using underscore prefixes (⇒Opcode Names Xtensa
Opcodes.), the '--no-transform' command-line option (*noteCommand Line
DONTPRINTYET 1DONTPRINTYET 11 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 (*note1DONTPRINTYET 1DONTPRINTYET 11 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.).
1
1 The 'MOVI' machine instruction can only materialize values in the
1 range from -2048 to 2047. Values outside this range are best
1 materialized with 'L32R' instructions. Thus:
1
1 movi a0, 100000
1
1 is assembled into the following machine code:
1
1 .literal .L1, 100000
1 l32r a0, .L1
1
1 The 'L8UI' machine instruction can only be used with immediate
1 offsets in the range from 0 to 255. The 'L16SI' and 'L16UI' machine
1 instructions can only be used with offsets from 0 to 510. The 'L32I'
1 machine instruction can only be used with offsets from 0 to 1020. A
1 load offset outside these ranges can be materialized with an 'L32R'
1 instruction if the destination register of the load is different than
1 the source address register. For example:
1
1 l32i a1, a0, 2040
1
1 is translated to:
1
1 .literal .L1, 2040
1 l32r a1, .L1
1 add a1, a0, a1
1 l32i a1, a1, 0
1
1 If the load destination and source address register are the same, an
1 out-of-range offset causes an error.
1
1 The Xtensa 'ADDI' instruction only allows immediate operands in the
1 range from -128 to 127. There are a number of alternate instruction
1 sequences for the 'ADDI' operation. First, if the immediate is 0, the
1 'ADDI' will be turned into a 'MOV.N' instruction (or the equivalent 'OR'
1 instruction if the code density option is not available). If the 'ADDI'
1 immediate is outside of the range -128 to 127, but inside the range
1 -32896 to 32639, an 'ADDMI' instruction or 'ADDMI'/'ADDI' sequence will
1 be used. Finally, if the immediate is outside of this range and a free
1 register is available, an 'L32R'/'ADD' sequence will be used with a
1 literal allocated from the literal pool.
1
1 For example:
1
1 addi a5, a6, 0
1 addi a5, a6, 512
1 addi a5, a6, 513
1 addi a5, a6, 50000
1
1 is assembled into the following:
1
1 .literal .L1, 50000
1 mov.n a5, a6
1 addmi a5, a6, 0x200
1 addmi a5, a6, 0x200
1 addi a5, a5, 1
1 l32r a5, .L1
1 add a5, a6, a5
1