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| author | Alan Modra <amodra@gmail.com> | 2020-09-27 19:11:58 +0930 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2020-11-03 09:36:40 +1030 |
| commit | 18963d3bee780cd8a6477ad5a198410758ec4e60 (patch) | |
| tree | cb7655415ee5b592ad09023beec1f1466cd365e1 /gcc/calls.h | |
| parent | 3ceaafc95c77cded164cde58da41bed0cbe76489 (diff) | |
| download | gcc-18963d3bee780cd8a6477ad5a198410758ec4e60.zip gcc-18963d3bee780cd8a6477ad5a198410758ec4e60.tar.gz gcc-18963d3bee780cd8a6477ad5a198410758ec4e60.tar.bz2 | |
can_implement_as_sibling_call_p REG_PARM_STACK_SPACE check
This moves an #ifdef block of code from calls.c to
targetm.function_ok_for_sibcall. Only two targets, x86 and rs6000,
define REG_PARM_STACK_SPACE or OUTGOING_REG_PARM_STACK_SPACE macros
that might vary depending on the called function. Macros like
UNITS_PER_WORD don't change over a function boundary, nor does the
MIPS ABI, nor does TARGET_64BIT on PA-RISC. Other targets are even
more trivially proven to not need the calls.c code.
Besides cleaning up a small piece of #ifdef code, the motivation for
this patch is to allow tail calls on PowerPC for functions that
require less reg_parm_stack_space than their caller. The original
code in calls.c only permitted tail calls when exactly equal, but on
PowerPC we can tail call if the callee has less or equal
REG_PARM_STACK_SPACE than the caller, as demonstrated by the
testcase. So we should use
/* If reg parm stack space increases, we cannot sibcall. */
if (REG_PARM_STACK_SPACE (decl ? decl : fntype)
> INCOMING_REG_PARM_STACK_SPACE (current_function_decl))
and note the change to use INCOMING_REG_PARM_STACK_SPACE.
REG_PARM_STACK_SPACE has always been wrong there for PowerPC. See
https://gcc.gnu.org/pipermail/gcc-patches/2014-May/389867.html for why
if you're curious. Not that it matters, because PowerPC can do
without this check entirely, relying on a stack slot test in generic
code.
a) The generic code checks that arg passing stack in the callee is not
greater than that in the caller, and,
b) ELFv2 only allocates reg_parm_stack_space when some parameter is
passed on the stack.
Point (b) means that zero reg_parm_stack_space implies zero stack
space, and non-zero reg_parm_stack_space implies non-zero stack
space. So the case of 0 reg_parm_stack_space in the caller and 64 in
the callee will be caught by (a).
gcc/
PR middle-end/97267
* calls.h (maybe_complain_about_tail_call): Declare.
* calls.c (maybe_complain_about_tail_call): Make global.
(can_implement_as_sibling_call_p): Delete reg_parm_stack_space
param. Adjust caller. Move REG_PARM_STACK_SPACE check to..
* config/i386/i386.c (ix86_function_ok_for_sibcall): ..here.
gcc/testsuite/
PR middle-end/97267
* gcc.target/powerpc/pr97267.c: New test.
Diffstat (limited to 'gcc/calls.h')
| -rw-r--r-- | gcc/calls.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/gcc/calls.h b/gcc/calls.h index f32b630..b20d24b 100644 --- a/gcc/calls.h +++ b/gcc/calls.h @@ -133,6 +133,7 @@ extern bool reference_callee_copied (CUMULATIVE_ARGS *, extern void maybe_warn_alloc_args_overflow (tree, tree, tree[2], int[2]); extern tree get_attr_nonstring_decl (tree, tree * = NULL); extern bool maybe_warn_nonstring_arg (tree, tree); +extern void maybe_complain_about_tail_call (tree, const char *); enum size_range_flags { /* Set to consider zero a valid range. */ |