[PATCH v3, c]: Fix PR c/39779, ICE shifting byte to the right with constant > 7FFFFFFF

[Uros Bizjak <ubizjak at gmail dot com>]

Hello!

This patch ensures that integer constant fits smaller type.
"short_shift" is set when integer constant > 0 by checking the sign
with tree_int_cst_sgn, and when "short_shift" is used, we re-check op1
with "compare_tree_int (op1, TYPE_PRECISION (TREE_TYPE (arg0))) < 0".
For some reason, tree_int_cst_sgn and compare_tree_int don't agree on
signedness of op1, leading to (kind of) invalid conversion of huge
negative value from QImode to QImode.

2009-09-21  Uros Bizjak  <ubizjak@gmail.com>

	PR c/39779
	* c-typeck.c (build_binary_op) <short_shift>: Check that integer
	constant fits in smaller type.

testsuite/ChangeLog:

2009-09-21  Uros Bizjak  <ubizjak@gmail.com>

	PR c/39779
	* gcc.c-torture/compile/pr39779.c: New test.

Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

OK for mainline and release branches?

Uros.

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