diff options
Diffstat (limited to 'gcc/simplify-rtx.c')
| -rw-r--r-- | gcc/simplify-rtx.c | 45 |
1 files changed, 15 insertions, 30 deletions
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index a0f1769..285f898 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -2343,41 +2343,26 @@ simplify_binary_operation (enum rtx_code code, enum machine_mode mode, break; case LSHIFTRT: - /* If shift count is undefined, don't fold it; let the machine do - what it wants. But truncate it if the machine will do that. */ - if (arg1 < 0) - return 0; - - if (SHIFT_COUNT_TRUNCATED) - arg1 %= width; - - val = ((unsigned HOST_WIDE_INT) arg0) >> arg1; - break; - case ASHIFT: - if (arg1 < 0) - return 0; - - if (SHIFT_COUNT_TRUNCATED) - arg1 %= width; - - val = ((unsigned HOST_WIDE_INT) arg0) << arg1; - break; - case ASHIFTRT: - if (arg1 < 0) - return 0; - + /* Truncate the shift if SHIFT_COUNT_TRUNCATED, otherwise make sure the + value is in range. We can't return any old value for out-of-range + arguments because either the middle-end (via shift_truncation_mask) + or the back-end might be relying on target-specific knowledge. + Nor can we rely on shift_truncation_mask, since the shift might + not be part of an ashlM3, lshrM3 or ashrM3 instruction. */ if (SHIFT_COUNT_TRUNCATED) - arg1 %= width; - - val = arg0s >> arg1; + arg1 = (unsigned HOST_WIDE_INT) arg1 % width; + else if (arg1 < 0 || arg1 >= GET_MODE_BITSIZE (mode)) + return 0; - /* Bootstrap compiler may not have sign extended the right shift. - Manually extend the sign to insure bootstrap cc matches gcc. */ - if (arg0s < 0 && arg1 > 0) - val |= ((HOST_WIDE_INT) -1) << (HOST_BITS_PER_WIDE_INT - arg1); + val = (code == ASHIFT + ? ((unsigned HOST_WIDE_INT) arg0) << arg1 + : ((unsigned HOST_WIDE_INT) arg0) >> arg1); + /* Sign-extend the result for arithmetic right shifts. */ + if (code == ASHIFTRT && arg0s < 0 && arg1 > 0) + val |= ((HOST_WIDE_INT) -1) << (width - arg1); break; case ROTATERT: |