Improved undefined-function backtrace on PPC.

[sbcl.git] / src / runtime / ppc-assem.S

diff --git a/src/runtime/ppc-assem.S b/src/runtime/ppc-assem.S
index 3f0dd99..32ec912 100644 (file)
--- a/src/runtime/ppc-assem.S
+++ b/src/runtime/ppc-assem.S
@@ -605,10 +605,23 @@ CSYMBOL(undefined_tramp):
        /* Point reg_CODE to the header and tag it as function, since
           the debugger regards a function pointer in reg_CODE which
           doesn't point to a code object as undefined function.  */
-       bcl 20,31,.+4                  /* get address of the next instruction */
-       mflr reg_CODE                  /* header 1 extra word back from here */
-       addi reg_CODE,reg_CODE,-(SIMPLE_FUN_CODE_OFFSET+4)
-       
+       /* We are given that reg_LIP points to undefined_tramp by
+          virtue of the calling convention.  */
+       addi reg_CODE,reg_LIP,-SIMPLE_FUN_CODE_OFFSET
+
+       /* If we are called with stack arguments (or in a tail-call
+          scenario), we end up with an allocated stack frame, but the
+          frame link information is uninitialized.  Fix things by
+          allocating and initializing our stack frame "properly". */
+       cmpwi cr0,reg_NARGS,16
+       bt gt,1f
+       addi reg_CSP,reg_CFP,16
+       b 2f
+1:     add reg_CSP,reg_CFP,reg_NARGS
+2:     stw reg_OCFP,0(reg_CFP)
+       stw reg_LRA,4(reg_CFP)
+
+       /* Now that the preliminaries are dealt with, actually trap. */
        twllei reg_ZERO,trap_Cerror
        .byte 4
        .byte UNDEFINED_FUN_ERROR