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| author | Richard Kenner <kenner@gcc.gnu.org> | 1992-09-23 19:23:19 -0400 |
|---|---|---|
| committer | Richard Kenner <kenner@gcc.gnu.org> | 1992-09-23 19:23:19 -0400 |
| commit | c3c2cb3741352a3794593654440ec0ea92e83825 (patch) | |
| tree | 9b2dc4229b47684cdc99b37b5eceb1bee034edb6 | |
| parent | d6749decf62e2f4bdca0f2586c05614cdb081c6a (diff) | |
| download | gcc-c3c2cb3741352a3794593654440ec0ea92e83825.zip gcc-c3c2cb3741352a3794593654440ec0ea92e83825.tar.gz gcc-c3c2cb3741352a3794593654440ec0ea92e83825.tar.bz2 | |
(significant_bits, num_sign_bit_copies): Handle SUBREGs made for promoted
variables.
From-SVN: r2215
| -rw-r--r-- | gcc/combine.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index 05c7c94..0442860 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -6083,6 +6083,14 @@ significant_bits (x, mode) break; case SUBREG: + /* If this is a SUBREG formed for a promoted variable that has + been zero-extended, we know that at least the high-order bits + are zero, though others might be too. */ + + if (SUBREG_PROMOTED_VAR_P (x) && SUBREG_PROMOTED_UNSIGNED_P (x)) + significant = (GET_MODE_MASK (GET_MODE (x)) + & significant_bits (SUBREG_REG (x), GET_MODE (x))); + /* If the inner mode is a single word for both the host and target machines, we can compute this from which bits of the inner object are known significant. */ @@ -6220,6 +6228,14 @@ num_sign_bit_copies (x, mode) return (sig == 0 ? bitwidth : bitwidth - floor_log2 (sig) - 1); case SUBREG: + /* If this is a SUBREG for a promoted object that is sign-extended + and we are looking at it in a wider mode, we know that at least the + high-order bits are known to be sign bit copies. */ + + if (SUBREG_PROMOTED_VAR_P (x) && ! SUBREG_PROMOTED_UNSIGNED_P (x)) + return (GET_MODE_BITSIZE (mode) - GET_MODE_BITSIZE (GET_MODE (x)) + + num_sign_bit_copies (SUBREG_REG (x), GET_MODE (x))); + /* For a smaller object, just ignore the high bits. */ if (bitwidth <= GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x)))) { |