#2585 Wrong result in left shift of int by int

[Philipp Klaus Krause]

In sdcc 3.6.5 #9842 for the following test fails (for at least hc08, stm8, mcs51-small) on my Debian GNU/Linux:

/*
   int cast issue
 */

#include <testfwk.h>

#include <limits.h>

void testBug (void)
{
  int i;

  i = SCHAR_MAX;

  ASSERT ((signed char)(i << (int)1) == -2);
}

(i << (int)1) should be 254, casting to signed char should yield -2. The test passes if the (int) is removed, or i is replaced by SCHAR_MAX.

Philipp

[Philipp Klaus Krause]

Looks like a CSE bug: dumpraw1 looks ok, while dumpcse has the bug.

Philipp

[Philipp Klaus Krause]

Increasing priority, since the fix to #2449 is blocked by this bug.

Philipp

[Maarten Brock]

I started looking into this. But I think things go wrong before CSE. This is what the AST looks like and that seems fine. Note the -2 to be a signed char. For simplicity I changed the ASSERT to a returned bool.

FUNCTION (_testBug=02E2D6F8) type (_Bool fixed) args (void)
tree (02E2E078) not decorated
(null):0:{ L1 B0
(null):0:  DECLARE SYMBOL (L1 B2 i=02BE6660) type (int fixed)
bug2585.c:11:  RETURN (02E2D450) type (bit fixed)
bug2585.c:11:    EQ(==) (02E2D3D0) type (bit fixed)
bug2585.c:11:      LEFT_SHIFT (02E2D150) type (signed-char fixed)
bug2585.c:11:        CAST (02E2DBF8) from type (int fixed) to type (signed-char fixed)
bug2585.c:11:          SYMBOL (L1 B2 i=02E2CF50 @ 02BE6660) type (int fixed)
bug2585.c:11:        CONSTANT (02E2D0D0) value = 1, 0x1, 1.000000 type (int literal)
bug2585.c:11:      CONSTANT (02E2D350) value = -2, 0xfffffffe, -2.000000 type (const-signed-char literal)
(null):0:}

[Maarten Brock]

Fixed in SDCC [r9881]