diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/combine.c | 11 |
2 files changed, 16 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e91ea00..0a56d77 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2013-05-04 Jakub Jelinek <jakub@redhat.com> + + * combine.c (combine_simplify_rtx) <case SUBREG>: If nonzero_bits + on op shows all bits zero in mode of a lowpart subreg, return zero. + 2013-05-03 Michael Meissner <meissner@linux.vnet.ibm.com> PR target/57150 diff --git a/gcc/combine.c b/gcc/combine.c index 0792ba3..b737bc5 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -5417,6 +5417,17 @@ combine_simplify_rtx (rtx x, enum machine_mode op0_mode, int in_dest, SUBREG_BYTE (x)); if (temp) return temp; + + /* If op is known to have all lower bits zero, the result is zero. */ + if (!in_dest + && SCALAR_INT_MODE_P (mode) + && SCALAR_INT_MODE_P (op0_mode) + && GET_MODE_PRECISION (mode) < GET_MODE_PRECISION (op0_mode) + && subreg_lowpart_offset (mode, op0_mode) == SUBREG_BYTE (x) + && HWI_COMPUTABLE_MODE_P (op0_mode) + && (nonzero_bits (SUBREG_REG (x), op0_mode) + & GET_MODE_MASK (mode)) == 0) + return CONST0_RTX (mode); } /* Don't change the mode of the MEM if that would change the meaning |