On Mon, May 30, 2011 at 07:35:58AM -0300, Alexandre Oliva wrote: > One of my patches for PR 48866 regressed guality/asm-1.c on > x86_64-linux-gnu because what used to be a single complex debug value > expression became a chain of debug temps holding simpler expressions, > and this chain exceeded the default recursion depth in resolving > location expressions. > > This patch introduces a param to control this depth, so that one can > trade compile time for better debug info, and bumps up the default depth > a bit, avoiding the regression. > > Regstrapped on x86_64-linux-gnu and i686-linux-gnu. Ok to install?
I support this, after all I had to bump it from 8 to 10 already in my http://gcc.gnu.org/ml/gcc-patches/2011-05/msg01182.html pending review. > for gcc/ChangeLog > from Alexandre Oliva <aol...@redhat.com> > > * params.def (PARAM_MAX_VARTRACK_EXPR_DEPTH): New. > * doc/invoke.texi: Document max-vartrack-expr-depth. > * var-tracking.c (EXPR_DEPTH): New. > (reverse_op, vt_expand_loc, vt_expand_loc_dummy): Use it. > > Index: gcc/params.def > =================================================================== > --- gcc/params.def.orig 2011-05-30 03:16:26.496342009 -0300 > +++ gcc/params.def 2011-05-30 03:35:17.852414343 -0300 > @@ -839,6 +839,14 @@ DEFPARAM (PARAM_MAX_VARTRACK_SIZE, > "Max. size of var tracking hash tables", > 50000000, 0, 0) > > +/* Set maximum recursion depth for var tracking expression expansion > + and resolution. */ > + > +DEFPARAM (PARAM_MAX_VARTRACK_EXPR_DEPTH, > + "max-vartrack-expr-depth", > + "Max. recursion depth for expanding var tracking expressions", > + 10, 0, 0) > + > /* Set minimum insn uid for non-debug insns. */ > > DEFPARAM (PARAM_MIN_NONDEBUG_INSN_UID, > Index: gcc/doc/invoke.texi > =================================================================== > --- gcc/doc/invoke.texi.orig 2011-05-30 03:40:14.716854423 -0300 > +++ gcc/doc/invoke.texi 2011-05-30 03:46:29.349288790 -0300 > @@ -8866,6 +8866,16 @@ the function. If the limit is exceeded > tracking analysis is completely disabled for the function. Setting > the parameter to zero makes it unlimited. > > +@item max-vartrack-expr-depth > +Sets a maximum number of recursion levels when attempting to map > +variable names or debug temporaries to value expressions. This trades > +compile time for more complete debug information. If this is set too > +low, value expressions that are available and could be represented in > +debug information may end up not being used; setting this higher may > +enable the compiler to find more complex debug expressions, but compile > +time may grow exponentially, and even then, it may fail to find more > +usable expressions. The default is 10. > + > @item min-nondebug-insn-uid > Use uids starting at this parameter for nondebug insns. The range below > the parameter is reserved exclusively for debug insns created by > Index: gcc/var-tracking.c > =================================================================== > --- gcc/var-tracking.c.orig 2011-05-30 03:40:46.135898766 -0300 > +++ gcc/var-tracking.c 2011-05-30 03:39:35.745798000 -0300 > @@ -5215,6 +5215,8 @@ add_uses_1 (rtx *x, void *cui) > for_each_rtx (x, add_uses, cui); > } > > +#define EXPR_DEPTH (PARAM_VALUE (PARAM_MAX_VARTRACK_EXPR_DEPTH)) > + > /* Attempt to reverse the EXPR operation in the debug info. Say for > reg1 = reg2 + 6 even when reg2 is no longer live we > can express its value as VAL - 6. */ > @@ -5286,7 +5288,7 @@ reverse_op (rtx val, const_rtx expr) > arg = XEXP (src, 1); > if (!CONST_INT_P (arg) && GET_CODE (arg) != SYMBOL_REF) > { > - arg = cselib_expand_value_rtx (arg, scratch_regs, 5); > + arg = cselib_expand_value_rtx (arg, scratch_regs, EXPR_DEPTH); > if (arg == NULL_RTX) > return NULL_RTX; > if (!CONST_INT_P (arg) && GET_CODE (arg) != SYMBOL_REF) > @@ -7416,7 +7418,7 @@ vt_expand_loc (rtx loc, htab_t vars, boo > data.dummy = false; > data.cur_loc_changed = false; > data.ignore_cur_loc = ignore_cur_loc; > - loc = cselib_expand_value_rtx_cb (loc, scratch_regs, 8, > + loc = cselib_expand_value_rtx_cb (loc, scratch_regs, EXPR_DEPTH, > vt_expand_loc_callback, &data); > > if (loc && MEM_P (loc)) > @@ -7438,7 +7440,7 @@ vt_expand_loc_dummy (rtx loc, htab_t var > data.dummy = true; > data.cur_loc_changed = false; > data.ignore_cur_loc = false; > - ret = cselib_dummy_expand_value_rtx_cb (loc, scratch_regs, 8, > + ret = cselib_dummy_expand_value_rtx_cb (loc, scratch_regs, EXPR_DEPTH, > vt_expand_loc_callback, &data); > *pcur_loc_changed = data.cur_loc_changed; > return ret; Jakub
