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alias.c (find_base_term): Improve handling of addresses constructed from binary operations.

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* alias.c (find_base_term): Improve handling of addresses
        constructed from binary operations.

From-SVN: r27263
This commit is contained in:
Jeffrey A Law 1999-05-30 23:51:39 +00:00 committed by Jeff Law
parent 71fb005652
commit 3c567fae5d
2 changed files with 54 additions and 4 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Mon May 31 00:46:17 1999 Jeffrey A Law (law@cygnus.com)
* alias.c (find_base_term): Improve handling of addresses
constructed from binary operations.
Sun May 30 14:29:17 1999 Eric Raskin (ehr@listworks.com) Sun May 30 14:29:17 1999 Eric Raskin (ehr@listworks.com)
* dgux.h (STARTFILE_SPEC): Fix incorrectly matched curly-braces. * dgux.h (STARTFILE_SPEC): Fix incorrectly matched curly-braces.

53
gcc/alias.c
View File

@ -746,10 +746,55 @@ find_base_term (x)
case PLUS: case PLUS:
case MINUS: case MINUS:
{ {
rtx tmp = find_base_term (XEXP (x, 0)); rtx tmp1 = XEXP (x, 0);
if (tmp) rtx tmp2 = XEXP (x, 1);
return tmp;
return find_base_term (XEXP (x, 1)); /* This is a litle bit tricky since we have to determine which of
the two operands represents the real base address. Otherwise this
routine may return the index register instead of the base register.
That may cause us to believe no aliasing was possible, when in
fact aliasing is possible.
We use a few simple tests to guess the base register. Additional
tests can certainly be added. For example, if one of the operands
is a shift or multiply, then it must be the index register and the
other operand is the base register. */
/* If either operand is known to be a pointer, then use it
to determine the base term. */
if (REG_P (tmp1) && REGNO_POINTER_FLAG (REGNO (tmp1)))
return find_base_term (tmp1);
if (REG_P (tmp2) && REGNO_POINTER_FLAG (REGNO (tmp2)))
return find_base_term (tmp2);
/* Neither operand was known to be a pointer. Go ahead and find the
base term for both operands. */
tmp1 = find_base_term (tmp1);
tmp2 = find_base_term (tmp2);
/* If either base term is named object or a special address
(like an argument or stack reference), then use it for the
base term. */
if (tmp1
&& (GET_CODE (tmp1) == SYMBOL_REF
|| GET_CODE (tmp1) == LABEL_REF
|| (GET_CODE (tmp1) == ADDRESS
&& GET_MODE (tmp1) != VOIDmode)))
return tmp1;
if (tmp2
&& (GET_CODE (tmp2) == SYMBOL_REF
|| GET_CODE (tmp2) == LABEL_REF
|| (GET_CODE (tmp2) == ADDRESS
&& GET_MODE (tmp2) != VOIDmode)))
return tmp2;
/* We could not determine which of the two operands was the
base register and which was the index. So we can determine
nothing from the base alias check. */
return 0;
} }
case AND: case AND: