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LLVM backend for 6502
2d2970905c
return argument pops the hidden struct pointer if present, not the caller.
For example, in this testcase:
struct X { int D, E, F, G; };
struct X bar() {
struct X a;
a.D = 0;
a.E = 1;
a.F = 2;
a.G = 3;
return a;
}
void foo(struct X *P) {
*P = bar();
}
We used to emit:
_foo:
subl $28, %esp
movl 32(%esp), %eax
movl %eax, (%esp)
call _bar
addl $28, %esp
ret
_bar:
movl 4(%esp), %eax
movl $0, (%eax)
movl $1, 4(%eax)
movl $2, 8(%eax)
movl $3, 12(%eax)
ret
This is correct on Linux/X86 but not Darwin/X86. With this patch, we now
emit:
_foo:
subl $28, %esp
movl 32(%esp), %eax
movl %eax, (%esp)
call _bar
*** addl $24, %esp
ret
_bar:
movl 4(%esp), %eax
movl $0, (%eax)
movl $1, 4(%eax)
movl $2, 8(%eax)
movl $3, 12(%eax)
*** ret $4
For the record, GCC emits (which is functionally equivalent to our new code):
_bar:
movl 4(%esp), %eax
movl $3, 12(%eax)
movl $2, 8(%eax)
movl $1, 4(%eax)
movl $0, (%eax)
ret $4
_foo:
pushl %esi
subl $40, %esp
movl 48(%esp), %esi
leal 16(%esp), %eax
movl %eax, (%esp)
call _bar
subl $4, %esp
movl 16(%esp), %eax
movl %eax, (%esi)
movl 20(%esp), %eax
movl %eax, 4(%esi)
movl 24(%esp), %eax
movl %eax, 8(%esi)
movl 28(%esp), %eax
movl %eax, 12(%esi)
addl $40, %esp
popl %esi
ret
This fixes SingleSource/Benchmarks/CoyoteBench/fftbench with LLC and the
JIT, and fixes the X86-backend portion of PR729. The CBE still needs to
be updated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28438 91177308-0d34-0410-b5e6-96231b3b80d8
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