Odd behaviour with OP_SCAST

[David Given <dg@cowlark.com>]

[-- Attachment #1: Type: text/plain, Size: 1557 bytes --]

test-unssa.c compiles this:

extern void func(int i, ...);
void foo(int i) { func(0, (float) i, (double) i, i); }

...into this:

	fpcast.64   %r3 <- (32) %arg1
	scast.64    %r5 <- (32) %arg1
	call        func, $0, %r3, %r5, %arg1
	ret

That's with the default settings. Unfortunately, with Clue,
sizeof(double) == sizeof(int), so that second instruction comes out as:

	scast.32    %r5 <- (32) %arg1

This then causes the simplification code in simplify_cast() to discard it:

	if (size == orig_size) {
		int op = (orig_type->ctype.modifiers & MOD_SIGNED) ? OP_SCAST : OP_CAST;
		if (insn->opcode == op)
			goto simplify;
	}

The end result is that my call statement turns into:

	call        func, $0, %r3, %arg1, %arg1

...which is wrong.

I assume that Clue's odd configuration is violating some assumption
somewhere, but I'm not well-enough versed with the sparse internals to
know where. It does seem odd to me that it's generating an OP_SCAST to
convert the int to a double, rather than an OP_FPCAST like in the float.
In the mean time, I've commented out the quoted stanza from
simplify_cast() on my setup, which makes things work, but that's not
really very pleasant.

Can anyone shed light on what might be happening here? Could this be a
symptom of some more serious underlying bug?

-- 
┌─── ｄｇ＠ｃｏｗｌａｒｋ．ｃｏｍ ───── http://www.cowlark.com ─────
│
│ "All power corrupts, but we need electricity." --- Diana Wynne Jones,
│ _Archer's Goon_


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 252 bytes --]