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2013 May 19
0
[LLVMdev] clobbering callee-save registers
...expect that on the x86-64, this function:
define i32 @testfun(i32 %arg)
{
tail call void asm sideeffect "" , "~{%r12},~{%r13}"()
ret i32 %arg
}
Would cause both r12 and r13 to be pushed in the prologue and popped before returning, but it actually just compiles into this:
_testfun: ## @testfun
Ltmp69:
## BB#0:
## InlineAsm Start
## InlineAsm End
movl>---%edi, %eax
ret
Ltmp70:
Just in case it was being very clever, I changed the assembly to actually clobber r12 and r13 with no effect.
So, first: am I misunderstanding the...