From fd304a932522a0d854fbe316429753f001e5b7de Mon Sep 17 00:00:00 2001 From: jakub Date: Sat, 4 May 2013 12:41:52 +0000 Subject: * combine.c (combine_simplify_rtx) : If nonzero_bits on op shows all bits zero in mode of a lowpart subreg, return zero. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198595 138bc75d-0d04-0410-961f-82ee72b054a4 --- gcc/combine.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'gcc/combine.c') diff --git a/gcc/combine.c b/gcc/combine.c index 0792ba3b6f4..b737bc5529f 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 -- cgit v1.2.1