From 40de22d6f926dadb38c5b6cf46703843e3d2d1e7 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Sat, 4 May 2013 14:41:52 +0200 Subject: [PATCH] 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) : If nonzero_bits on op shows all bits zero in mode of a lowpart subreg, return zero. From-SVN: r198595 --- gcc/ChangeLog | 5 +++++ gcc/combine.c | 11 +++++++++++ 2 files changed, 16 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e91ea0027bbb..0a56d776b5f9 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2013-05-04 Jakub Jelinek + + * combine.c (combine_simplify_rtx) : If nonzero_bits + on op shows all bits zero in mode of a lowpart subreg, return zero. + 2013-05-03 Michael Meissner PR target/57150 diff --git a/gcc/combine.c b/gcc/combine.c index 0792ba3b6f41..b737bc5529fc 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