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  1. Embedded Software & Tools
  2. EXT_EP-9737

Stack usage incorrect on many hand-coded assembly library functions

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    • Bug
    • Status: Fixed
    • Medium
    • Resolution: Fixed
    • Code Generation Tools
    • CODEGEN-6690
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      ARM_18.1.0.LTS
      ARM_18.12.0.LTS
      ARM_20.2.0.LTS
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      ARM_18.1.0.LTS ARM_18.12.0.LTS ARM_20.2.0.LTS
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      ARM_20.2.1.LTS*
      ARM_18.12.6.LTS*
      ARM_18.1.8.LTS*
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      ARM_20.2.1.LTS* ARM_18.12.6.LTS* ARM_18.1.8.LTS*
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      The worst case stack usage for most hand-coded assembly functions in the RTS library is recorded in an assembler directive. This value ends up in the DWARF information and is used by tools such as the call graph utillity. For many functions, this worst case usage was found to be inaccurate. Functions compiled from C or C++ code are not affected.
      Show
      The worst case stack usage for most hand-coded assembly functions in the RTS library is recorded in an assembler directive. This value ends up in the DWARF information and is used by tools such as the call graph utillity. For many functions, this worst case usage was found to be inaccurate. Functions compiled from C or C++ code are not affected.

    Description

      The Thumb2 variant of memcpy is in the source file memcpy_t2.asm. The function starts with these lines ...

      __TI_C$MEMCPY: .asmfunc stack_usage(0)
        CMP     r2, #0                  ; CHECK FOR n == 0

      However, later in the function there is this ...

      _ovr16:	PUSH	{r4 - r6}		; COPYING 16 BYTES OR MORE.
	SUBS	r2, #16			;
_lp16:	LDMIA	r1!, {r3 - r6}		;
	STMIA	r0!, {r3 - r6}		;
	SUBS	r2, #16			;
	BCS	_lp16			;
	POP	{r4 - r6}		; RESTORE THE SAVED REGISTERS AND

      Note the 3 registers R4, R5, R6 are pushed and popped from the stack.  Therefore, the stack usage is not 0, but 12 bytes.

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            syncuser TI User
            syncuser TI User
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            Dates

              Created:
              Updated:
              Resolved: