[v1,1/4] Improve must tail in RTL backend
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| linaro-tcwg-bot/tcwg_gcc_build--master-arm |
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| linaro-tcwg-bot/tcwg_gcc_build--master-aarch64 |
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| linaro-tcwg-bot/tcwg_gcc_check--master-arm |
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Commit Message
- Give error messages for all causes of non sibling call generation
- Don't override choices of other non sibling call checks with
must tail. This causes ICEs. The must tail attribute now only
overrides flag_optimize_sibling_calls locally.
- 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 (this could be improved, but it's already useful without
that) tree-tailcall usually fails without optimization, so must
adjust the existing must-tail plugin test to specify -O2.
---
gcc/calls.cc | 31 +++++++++++++------
.../gcc.dg/plugin/must-tail-call-1.c | 1 +
2 files changed, 22 insertions(+), 10 deletions(-)
@@ -2650,7 +2650,9 @@ 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. */
+ if (!try_tail_call)
+ maybe_complain_about_tail_call (exp, "cannot tail-call: other reasons");
int pass;
/* Register in which non-BLKmode value will be returned,
@@ -3021,10 +3023,22 @@ 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, "cannot tail-call: 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)
+ {
+ /* ??? correct message? */
+ maybe_complain_about_tail_call (exp, "cannot tail-call: stack space needed");
+ try_tail_call = 0;
+ }
+ if (dbg_cnt (tail_call) == false)
try_tail_call = 0;
/* Workaround buggy C/C++ wrappers around Fortran routines with
@@ -3045,15 +3059,12 @@ expand_call (tree exp, rtx target, int ignore)
if (MEM_P (*iter))
{
try_tail_call = 0;
+ maybe_complain_about_tail_call (exp,
+ "cannot tail-call: hidden string length argument");
break;
}
}
- /* If the user has marked the function as requiring tail-call
- optimization, attempt it. */
- if (must_tail_call)
- try_tail_call = 1;
-
/* Rest of purposes for tail call optimizations to fail. */
if (try_tail_call)
try_tail_call = can_implement_as_sibling_call_p (exp,
@@ -1,4 +1,5 @@
/* { dg-do compile { target tail_call } } */
+/* { dg-options "-O2" } */
/* { dg-options "-fdelayed-branch" { target sparc*-*-* } } */
extern void abort (void);