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| author | Jakub Jelinek <jakub@redhat.com> | 2013-05-04 14:41:52 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2013-05-04 14:41:52 +0200 |
| commit | 40de22d6f926dadb38c5b6cf46703843e3d2d1e7 (patch) | |
| tree | 268423f878efbc6f96e2577bc8b63cfd72fe0f6a /gcc/combine.c | |
| parent | 71871e37d9e1c8cd59943e9e1b94087f23e6333e (diff) | |
| download | gcc-40de22d6f926dadb38c5b6cf46703843e3d2d1e7.zip gcc-40de22d6f926dadb38c5b6cf46703843e3d2d1e7.tar.gz gcc-40de22d6f926dadb38c5b6cf46703843e3d2d1e7.tar.bz2 | |
combine.c (combine_simplify_rtx): If nonzero_bits on op shows all bits zero in mode of a lowpart subreg, return zero.
* combine.c (combine_simplify_rtx) <case SUBREG>: If nonzero_bits
on op shows all bits zero in mode of a lowpart subreg, return zero.
From-SVN: r198595
Diffstat (limited to 'gcc/combine.c')
| -rw-r--r-- | gcc/combine.c | 11 |
1 files changed, 11 insertions, 0 deletions
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 |