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| author | Roger Sayle <roger@eyesopen.com> | 2004-03-11 17:45:03 +0000 |
|---|---|---|
| committer | Roger Sayle <sayle@gcc.gnu.org> | 2004-03-11 17:45:03 +0000 |
| commit | 239a625ee83ff08df15beab3ca2f1b37881e7f10 (patch) | |
| tree | 53c0a411f358defff23d8e0c39b1dc0819424479 /gcc/simplify-rtx.c | |
| parent | 4b0b51c9706b25603247ec6e48d8ac53e8db64f3 (diff) | |
| download | gcc-239a625ee83ff08df15beab3ca2f1b37881e7f10.tar.gz | |
fold-const.c (negate_expr_p): We can optimize -((int)X>>C) where C is an integer constant one bit less than...
* fold-const.c (negate_expr_p) <RSHIFT_EXPR>: We can optimize
-((int)X>>C) where C is an integer constant one bit less than the
size of X into (unsigned)X>>C. Similarly for unsigned->signed.
(negate_expr) <RSHIFT_EXPR>: Implement the above transformations.
* simplify-rtx.c (simplify_unary_operation): Also implement the
above transformations at the RTL level.
* gcc.c-torture/execute/20040311-1.c: New test case.
From-SVN: r79334
Diffstat (limited to 'gcc/simplify-rtx.c')
| -rw-r--r-- | gcc/simplify-rtx.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 3647c244077..2846bb7a80d 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -1013,6 +1013,22 @@ simplify_unary_operation (enum rtx_code code, enum machine_mode mode, XEXP (op, 1)); } + /* (neg (ashiftrt X C)) can be replaced by (lshiftrt X C) when + C is equal to the width of MODE minus 1. */ + if (GET_CODE (op) == ASHIFTRT + && GET_CODE (XEXP (op, 1)) == CONST_INT + && INTVAL (XEXP (op, 1)) == GET_MODE_BITSIZE (mode) - 1) + return simplify_gen_binary (LSHIFTRT, mode, + XEXP (op, 0), XEXP (op, 1)); + + /* (neg (lshiftrt X C)) can be replaced by (ashiftrt X C) when + C is equal to the width of MODE minus 1. */ + if (GET_CODE (op) == LSHIFTRT + && GET_CODE (XEXP (op, 1)) == CONST_INT + && INTVAL (XEXP (op, 1)) == GET_MODE_BITSIZE (mode) - 1) + return simplify_gen_binary (ASHIFTRT, mode, + XEXP (op, 0), XEXP (op, 1)); + break; case SIGN_EXTEND: |