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Diffstat (limited to 'docs/reference/asm_thumb2_label_branch.rst')
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diff --git a/docs/reference/asm_thumb2_label_branch.rst b/docs/reference/asm_thumb2_label_branch.rst deleted file mode 100644 index 8c85e55f0..000000000 --- a/docs/reference/asm_thumb2_label_branch.rst +++ /dev/null @@ -1,85 +0,0 @@ -Branch instructions -=================== - -These cause execution to jump to a target location usually specified by a label (see the ``label`` -assembler directive). Conditional branches and the ``it`` and ``ite`` instructions test -the Application Program Status Register (APSR) N (negative), Z (zero), C (carry) and V -(overflow) flags to determine whether the branch should be executed. - -Most of the exposed assembler instructions (including move operations) set the flags but -there are explicit comparison instructions to enable values to be tested. - -Further detail on the meaning of the condition flags is provided in the section -describing comparison functions. - -Document conventions --------------------- - -Notation: ``Rm`` denotes ARM registers R0-R15. ``LABEL`` denotes a label defined with the -``label()`` assembler directive. ``<condition>`` indicates one of the following condition -specifiers: - -* eq Equal to (result was zero) -* ne Not equal -* cs Carry set -* cc Carry clear -* mi Minus (negative) -* pl Plus (positive) -* vs Overflow set -* vc Overflow clear -* hi > (unsigned comparison) -* ls <= (unsigned comparison) -* ge >= (signed comparison) -* lt < (signed comparison) -* gt > (signed comparison) -* le <= (signed comparison) - -Branch to label ---------------- - -* b(LABEL) Unconditional branch -* beq(LABEL) branch if equal -* bne(LABEL) branch if not equal -* bge(LABEL) branch if greater than or equal -* bgt(LABEL) branch if greater than -* blt(LABEL) branch if less than (<) (signed) -* ble(LABEL) branch if less than or equal to (<=) (signed) -* bcs(LABEL) branch if carry flag is set -* bcc(LABEL) branch if carry flag is clear -* bmi(LABEL) branch if negative -* bpl(LABEL) branch if positive -* bvs(LABEL) branch if overflow flag set -* bvc(LABEL) branch if overflow flag is clear -* bhi(LABEL) branch if higher (unsigned) -* bls(LABEL) branch if lower or equal (unsigned) - -Long branches -------------- - -The code produced by the branch instructions listed above uses a fixed bit width to specify the -branch destination, which is PC relative. Consequently in long programs where the -branch instruction is remote from its destination the assembler will produce a "branch not in -range" error. This can be overcome with the "wide" variants such as - -* beq\_w(LABEL) long branch if equal - -Wide branches use 4 bytes to encode the instruction (compared with 2 bytes for standard branch instructions). - -Subroutines (functions) ------------------------ - -When entering a subroutine the processor stores the return address in register r14, also -known as the link register (lr). Return to the instruction after the subroutine call is -performed by updating the program counter (r15 or pc) from the link register, This -process is handled by the following instructions. - -* bl(LABEL) - -Transfer execution to the instruction after ``LABEL`` storing the return address in -the link register (r14). - -* bx(Rm) Branch to address specified by Rm. - -Typically ``bx(lr)`` is issued to return from a subroutine. For nested subroutines the -link register of outer scopes must be saved (usually on the stack) before performing -inner subroutine calls. |