[LLVMdev] ARM eabi calling convention

[Akira Hatanaka]

When I compile this program

*$ cat vararg1-main.c

typedef struct {
  double d;
} S0;

S0 g1;

void foo0(int a, ...);

int main(int argc, char **argv) {
  S0 s0 = { 2.0 };

  foo0(1, s0);

  printf("%f\n", g1.d);

* *   return 0;
}*

with this command,

*$ clang  -target arm-none-linux-gnueabi-gcc  -ccc-clang-archs armv7
-emit-llvm vararg1-main.c  -S -o vararg1-main.ll -O3*

I get this bitcode.

*$ cat vararg1-main.ll

define arm_aapcscc i32 @main(i32 %argc, i8** nocapture %argv) nounwind {
entry:
  %0 = load [2 x i32]* bitcast (%struct.S0* @main.s0 to [2 x i32]*), align 8
  tail call arm_aapcscc  void (i32, ...)* @foo0(i32 1, [2 x i32] %0)
nounwind
  %1 = load double* getelementptr inbounds (%struct.S0* @g1, i32 0, i32 0),
align 8, !tbaa !0
  %call = tail call arm_aapcscc  i32 (i8*, ...)* @printf(i8* getelementptr
inbounds ([4 x i8]* @.str, i32 0, i32 0), double %1) nounwind
  ret i32 0
}*

My understanding is that ARM eabi requires that structure S0 be 8-byte
aligned when it is passed to function foo0, i.e. it should be passed in
register r2 and r3.

Is there anything in the call to foo0 that informs the backend that %0
should be 8-byte aligned?

*  tail call arm_aapcscc  void (i32, ...)* @foo0(i32 1, [2 x i32] %0)
nounwind
*
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