[Bug middle-end/51994] [4.6/4.7 Regression] git-1.7.8.3 miscompiled due to negative bitpos from get_inner_reference

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51994

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
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  Attachment #26462|0                           |1
        is obsolete|                            |

--- Comment #12 from Uros Bizjak <ubizjak at gmail dot com> 2012-01-25 18:17:25 UTC ---
Created attachment 26466
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26466
WIP gcc-46 patch, includes other expmed.c store/extract bit functions

This patch fixes regression at gcc.dg/pr48335-8.c on x86_64-linux from previous
patch. However, some kind of unterminated loop is now triggered for this test
on x86_64 target:

(gdb) up
#2  0x00000000005b1a3d in extract_split_bit_field (op0=0x7ffff1340a80,
bitsize=16, bitpos=-24, unsignedp=1)
    at ../../gcc-svn/branches/gcc-4_6-branch/gcc/expmed.c:1996
1996              word = operand_subword_force (op0, offset, GET_MODE (op0));
(gdb) up
#3  0x00000000005b1962 in extract_split_bit_field (op0=0x7ffff1340a80,
bitsize=16, bitpos=-24, unsignedp=1)
    at ../../gcc-svn/branches/gcc-4_6-branch/gcc/expmed.c:2006
2006          part = extract_fixed_bit_field (word_mode, word,
(gdb) up
#4  0x00000000005b1962 in extract_split_bit_field (op0=0x7ffff1340a80,
bitsize=16, bitpos=-24, unsignedp=1)
    at ../../gcc-svn/branches/gcc-4_6-branch/gcc/expmed.c:2006
2006          part = extract_fixed_bit_field (word_mode, word,

I was not able to fix it... definitelly for someone more experienced in this
area of the compiler.