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Re: [PATCH] Handle BOOLEAN_TYPEs in c_common_type
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Roger Sayle <roger at eyesopen dot com>
- Cc: Richard Henderson <rth at redhat dot com>, gcc-patches at gcc dot gnu dot org
- Date: Mon, 16 May 2005 16:43:13 +0000 (UTC)
- Subject: Re: [PATCH] Handle BOOLEAN_TYPEs in c_common_type
- References: <Pine.LNX.firstname.lastname@example.org>
On Mon, 16 May 2005, Roger Sayle wrote:
> With my local changes to the tree, the failing testcase is
> gcc.c-torture/execute/20030714-1.c. The sequence of events is that
> build_binary_op attempts to construct a NE_EXPR operation on two
> QImode Boolean values that have been promoted to SImode integers
> following the usual conversion rules. Line 7857 of build_binary_op
> calls shorten_compare on the integer operands, and then in
> c-common.c:shorten_compare, we call get_narrower to reduce the
> promoted arguments to their unwidened forms. In this case, although
> op0 and op1 are integer types, the results of get_narrower, primop0
> and primop1 are now Boolean types.
> Finally, on line 2158 of shorten_compare, we end up calling
> type = common_type (TREE_TYPE (primop0), TREE_TYPE (primop1));
> And by passing two unpromoted Booleans to c_common_type, we ICE.
I think the real underlying problem is that the optimizations in
shorten_compare are language-dependent and call language-dependent
functions such as common_type. It ought to be possible to do such
optimizations in language-independent code. But this is a separate issue.
> The possible solutions are (i) that get_narrower shouldn't strip
> the Boolean to integer conversions, (ii) shorten_compare should
> guard against BOOLEAN_TYPE before calling common_type, (iii)
> that common_type and not c_common_type should handle Booleans
> (as proposed by Joseph) or (iv) my original patch that extends
> the functionality of c_common_type.
c_common_type has a well-defined interface. common_type is a kludge
wrapping around that to deal with the requirements of shorten_compare. So
I think common_type is the right place.
Joseph S. Myers http://www.srcf.ucam.org/~jsm28/gcc/
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