fix issue open64-compiler#35 for WHIRL2llvm

The offset is the distance between the field of struct and the start of struct,
but the parameter just be pushed one time if the parameter just hold one register.
So we need to align down the offset of field to register size.

1. The w2ll will crash if compile the code like that:
```
typedef struct quantum_matrix_struct {
  int rows;
  int cols;
} quantum_matrix;

void
quantum_print_matrix(quantum_matrix m)
{
  int i, j;
  for(i=0; i<m.rows; i++)
  {
    for(j=0; j<m.cols; j++) {
        printf("%d\n", 1);
    }
  }
}
```

2. Error Log:
```
Find_parm_type cannot find
```

Signed-off-by: Zhijin Zeng <[email protected]>

Author: zengdage

osprey/ir_tools/whirl2llvm.cxx

@@ -116,6 +116,7 @@ BOOL Run_vsaopt = FALSE;      // hack to workaround undefine since
 # define Is_True(a, b)  ((void)1)
 #endif
 
+#define ALIGNMENT_DOWN(a, size) (a & (~(size-1)))
 
 static INT Compiler_Line = 0;
 static const char *Compiler_File = NULL;
@@ -4220,6 +4221,13 @@ WHIRL2llvm::WN2llvmSymAct(WN *wn, ACTION act, LVVAL *rhs)
     }  // end of GLOBAL_SYMTAB
     case SCLASS_FORMAL: {
       LVALC *arg_addr = nullptr;
+
+      if (Fix_TY_mtype(WN_type(wn)) != MTYPE_UNKNOWN) {
+        PLOC ploc = Get_Input_Parameter_Location(WN_type(wn));
+        if (Mload_ty(WN_type(wn)))
+          offset = ALIGNMENT_DOWN(offset, PLOC_size(ploc));
+      }
+
       CONSTSTR var = Adjust_parm_name(varname, offset);
       BOOL on_stack = FALSE;
       TY_IDX parmtype = Find_parm_type(var, &on_stack);