| Message ID | 20240622185557.1589179-2-ak@linux.intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v8,01/12] Improve must tail in RTL backend | expand |
On Sat, Jun 22, 2024 at 8:57 PM Andi Kleen <ak@linux.intel.com> wrote: > > - Give error messages for all causes of non sibling call generation > - When giving error messages clear the musttail flag to avoid ICEs > - Error out when tree-tailcall failed to mark a must-tail call > sibcall. In this case it doesn't know the true reason and only gives > a vague message. We seem to have concluded that we need the tailcall pass run and both markings after all. Thus OK. Richard. > PR83324 > > gcc/ChangeLog: > > * calls.cc (maybe_complain_about_tail_call): Clear must tail > flag on error. > (expand_call): Give error messages for all musttail failures. > --- > gcc/calls.cc | 32 ++++++++++++++++++++++++++------ > 1 file changed, 26 insertions(+), 6 deletions(-) > > diff --git a/gcc/calls.cc b/gcc/calls.cc > index 21d78f9779fe..883eb9971257 100644 > --- a/gcc/calls.cc > +++ b/gcc/calls.cc > @@ -1249,6 +1249,7 @@ maybe_complain_about_tail_call (tree call_expr, const char *reason) > return; > > error_at (EXPR_LOCATION (call_expr), "cannot tail-call: %s", reason); > + CALL_EXPR_MUST_TAIL_CALL (call_expr) = 0; > } > > /* Fill in ARGS_SIZE and ARGS array based on the parameters found in > @@ -2650,7 +2651,13 @@ expand_call (tree exp, rtx target, int ignore) > /* The type of the function being called. */ > tree fntype; > bool try_tail_call = CALL_EXPR_TAILCALL (exp); > - bool must_tail_call = CALL_EXPR_MUST_TAIL_CALL (exp); > + /* tree-tailcall decided not to do tail calls. Error for the musttail case, > + unfortunately we don't know the reason so it's fairly vague. > + When tree-tailcall reported an error it already cleared the flag, > + so this shouldn't really happen unless the > + the musttail pass gave up walking before finding the call. */ > + if (!try_tail_call) > + maybe_complain_about_tail_call (exp, "other reasons"); > int pass; > > /* Register in which non-BLKmode value will be returned, > @@ -3022,10 +3029,21 @@ expand_call (tree exp, rtx target, int ignore) > pushed these optimizations into -O2. Don't try if we're already > expanding a call, as that means we're an argument. Don't try if > there's cleanups, as we know there's code to follow the call. */ > - if (currently_expanding_call++ != 0 > - || (!flag_optimize_sibling_calls && !CALL_FROM_THUNK_P (exp)) > - || args_size.var > - || dbg_cnt (tail_call) == false) > + if (currently_expanding_call++ != 0) > + { > + maybe_complain_about_tail_call (exp, "inside another call"); > + try_tail_call = 0; > + } > + if (!flag_optimize_sibling_calls > + && !CALL_FROM_THUNK_P (exp) > + && !CALL_EXPR_MUST_TAIL_CALL (exp)) > + try_tail_call = 0; > + if (args_size.var) > + { > + maybe_complain_about_tail_call (exp, "variable size arguments"); > + try_tail_call = 0; > + } > + if (dbg_cnt (tail_call) == false) > try_tail_call = 0; > > /* Workaround buggy C/C++ wrappers around Fortran routines with > @@ -3046,13 +3064,15 @@ expand_call (tree exp, rtx target, int ignore) > if (MEM_P (*iter)) > { > try_tail_call = 0; > + maybe_complain_about_tail_call (exp, > + "hidden string length argument passed on stack"); > break; > } > } > > /* If the user has marked the function as requiring tail-call > optimization, attempt it. */ > - if (must_tail_call) > + if (CALL_EXPR_MUST_TAIL_CALL (exp)) > try_tail_call = 1; > > /* Rest of purposes for tail call optimizations to fail. */ > -- > 2.45.2 >
diff --git a/gcc/calls.cc b/gcc/calls.cc index 21d78f9779fe..883eb9971257 100644 --- a/gcc/calls.cc +++ b/gcc/calls.cc @@ -1249,6 +1249,7 @@ maybe_complain_about_tail_call (tree call_expr, const char *reason) return; error_at (EXPR_LOCATION (call_expr), "cannot tail-call: %s", reason); + CALL_EXPR_MUST_TAIL_CALL (call_expr) = 0; } /* Fill in ARGS_SIZE and ARGS array based on the parameters found in @@ -2650,7 +2651,13 @@ expand_call (tree exp, rtx target, int ignore) /* The type of the function being called. */ tree fntype; bool try_tail_call = CALL_EXPR_TAILCALL (exp); - bool must_tail_call = CALL_EXPR_MUST_TAIL_CALL (exp); + /* tree-tailcall decided not to do tail calls. Error for the musttail case, + unfortunately we don't know the reason so it's fairly vague. + When tree-tailcall reported an error it already cleared the flag, + so this shouldn't really happen unless the + the musttail pass gave up walking before finding the call. */ + if (!try_tail_call) + maybe_complain_about_tail_call (exp, "other reasons"); int pass; /* Register in which non-BLKmode value will be returned, @@ -3022,10 +3029,21 @@ expand_call (tree exp, rtx target, int ignore) pushed these optimizations into -O2. Don't try if we're already expanding a call, as that means we're an argument. Don't try if there's cleanups, as we know there's code to follow the call. */ - if (currently_expanding_call++ != 0 - || (!flag_optimize_sibling_calls && !CALL_FROM_THUNK_P (exp)) - || args_size.var - || dbg_cnt (tail_call) == false) + if (currently_expanding_call++ != 0) + { + maybe_complain_about_tail_call (exp, "inside another call"); + try_tail_call = 0; + } + if (!flag_optimize_sibling_calls + && !CALL_FROM_THUNK_P (exp) + && !CALL_EXPR_MUST_TAIL_CALL (exp)) + try_tail_call = 0; + if (args_size.var) + { + maybe_complain_about_tail_call (exp, "variable size arguments"); + try_tail_call = 0; + } + if (dbg_cnt (tail_call) == false) try_tail_call = 0; /* Workaround buggy C/C++ wrappers around Fortran routines with @@ -3046,13 +3064,15 @@ expand_call (tree exp, rtx target, int ignore) if (MEM_P (*iter)) { try_tail_call = 0; + maybe_complain_about_tail_call (exp, + "hidden string length argument passed on stack"); break; } } /* If the user has marked the function as requiring tail-call optimization, attempt it. */ - if (must_tail_call) + if (CALL_EXPR_MUST_TAIL_CALL (exp)) try_tail_call = 1; /* Rest of purposes for tail call optimizations to fail. */
- Give error messages for all causes of non sibling call generation - When giving error messages clear the musttail flag to avoid ICEs - Error out when tree-tailcall failed to mark a must-tail call sibcall. In this case it doesn't know the true reason and only gives a vague message. PR83324 gcc/ChangeLog: * calls.cc (maybe_complain_about_tail_call): Clear must tail flag on error. (expand_call): Give error messages for all musttail failures. --- gcc/calls.cc | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-)