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(convert_to_integer): Don't pass truncation thru lshift if shift count >= width of narrower type.

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(convert_to_integer): Don't pass truncation thru lshift
if shift count >= width of narrower type.  Instead, just use 0.

From-SVN: r2104
This commit is contained in:
Richard Stallman 1992-09-11 07:35:32 +00:00
parent 4f61da45f3
commit 1f0c5cc9cf
1 changed files with 15 additions and 3 deletions
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18
gcc/c-convert.c
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@ -187,9 +187,21 @@ convert_to_integer (type, expr)
/* We can pass truncation down through left shifting
when the shift count is a nonnegative constant. */
if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
&& ! tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_zero_node))
/* In this case, shifting is like multiplication. */
goto trunc1;
&& ! tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_zero_node)
&& TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
{
/* If shift count is less than the width of the truncated type,
really shift. */
if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
/* In this case, shifting is like multiplication. */
goto trunc1;
else
/* If it is >= that width, result is zero.
Handling this with trunc1 would give the wrong result:
(int) ((long long) a << 32) is well defined (as 0)
but (int) a << 32 is undefined and would get a warning. */
return convert_to_integer (type, integer_zero_node);
}
break;
case MAX_EXPR: