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function.c (gen_mem_addressof): If the address REG is REG_USERVAR_P make the new REG be so also.

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* function.c (gen_mem_addressof): If the address REG is
	REG_USERVAR_P make the new REG be so also.
	* loop.c (scan_loop): Apply DeMorgan's laws and add documentation
	in an attempt to clarify slightly.

From-SVN: r22667
This commit is contained in:
Mark Mitchell 1998-09-30 10:10:02 +00:00 committed by Mark Mitchell
parent ee06cc21bf
commit 95ca22f405
4 changed files with 56 additions and 14 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
Wed Sep 30 10:09:39 1998 Mark Mitchell <mark@markmitchell.com>
* function.c (gen_mem_addressof): If the address REG is
REG_USERVAR_P make the new REG be so also.
* loop.c (scan_loop): Apply DeMorgan's laws and add documentation
in an attempt to clarify slightly.
Wed Sep 30 09:57:40 1998 Jeffrey A Law (law@cygnus.com)
* expr.c (expand_expr): Handle COMPONENT_REF, BIT_FIELD_REF ARRAY_REF

4
gcc/function.c
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@ -2756,9 +2756,11 @@ gen_mem_addressof (reg, decl)
tree decl;
{
tree type = TREE_TYPE (decl);
rtx r = gen_rtx_ADDRESSOF (Pmode, gen_reg_rtx (GET_MODE (reg)), REGNO (reg));
SET_ADDRESSOF_DECL (r, decl);
/* If the original REG was a user-variable, then so is the REG whose
address is being taken. */
REG_USERVAR_P (XEXP (r, 0)) = REG_USERVAR_P (reg);
XEXP (reg, 0) = r;
PUT_CODE (reg, MEM);

38
gcc/loop.c
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@ -871,19 +871,31 @@ scan_loop (loop_start, end, unroll_p, bct_p)
We don't know its life-span, so we can't compute the benefit. */
if (REGNO (SET_DEST (set)) >= max_reg_before_loop)
;
/* In order to move a register, we need to have one of three cases:
(1) it is used only in the same basic block as the set
(2) it is not a user variable and it is not used in the
exit test (this can cause the variable to be used
before it is set just like a user-variable).
(3) the set is guaranteed to be executed once the loop starts,
and the reg is not used until after that. */
else if (! ((! maybe_never
&& ! loop_reg_used_before_p (set, p, loop_start,
scan_start, end))
|| (! REG_USERVAR_P (SET_DEST (set))
&& ! REG_LOOP_TEST_P (SET_DEST (set)))
|| reg_in_basic_block_p (p, SET_DEST (set))))
else if (/* The set is a user-variable or it is used in
the exit test (this can cause the variable to be
used before it is set just like a
user-variable)... */
(REG_USERVAR_P (SET_DEST (set))
|| REG_LOOP_TEST_P (SET_DEST (set)))
/* And the set is not guaranteed to be executed one
the loop starts, or the value before the set is
needed before the set occurs... */
&& (maybe_never
|| loop_reg_used_before_p (set, p, loop_start,
scan_start, end))
/* And the register is used in basic blocks other
than the one where it is set (meaning that
something after this point in the loop might
depend on its value before the set). */
&& !reg_in_basic_block_p (p, SET_DEST (set)))
/* It is unsafe to move the set. The fact that these
three conditions are considered in conjunction means
that we are assuming various conditions, such as:
o It's OK to move a set of a variable which was not
created by the user and is not used in an exit test
even if that point in the set would not be reached
during execution of the loop. */
;
else if ((tem = invariant_p (src))
&& (dependencies == 0

21
gcc/testsuite/gcc.c-torture/execute/980929-1.c Normal file
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@ -0,0 +1,21 @@
void f(int i)
{
if (i != 1000)
abort ();
}
int main()
{
int n=1000;
int i;
f(n);
for(i=0; i<1; ++i) {
f(n);
n=666;
&n;
}
exit (0);
}