cse.c (find_comparison_args): Update documentation.
* cse.c (find_comparison_args): Update documentation. Fix mishandling of COMPARE operations. * tree.def (ABS_EXPR): Add documentation. * fold-const.c (fold): Improve folding of ABS_EXPRs. From-SVN: r40630
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Mark Mitchell
Mark Mitchell
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2001-03-19 Mark Mitchell <mark@codesourcery.com>
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* cse.c (find_comparison_args): Update documentation. Fix
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mishandling of COMPARE operations.
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* tree.def (ABS_EXPR): Add documentation.
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* fold-const.c (fold): Improve folding of ABS_EXPRs.
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2001-03-19 Zack Weinberg <zackw@stanford.edu>
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* Makefile.in (hash.o): Depend on $(GCONFIG_H), not $(CONFIG_H).
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78
gcc/cse.c
78
gcc/cse.c
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@ -3086,17 +3086,25 @@ find_best_addr (insn, loc, mode)
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#endif
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}
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/* Given an operation (CODE, *PARG1, *PARG2), where code is a comparison
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operation (EQ, NE, GT, etc.), follow it back through the hash table and
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what values are being compared.
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/* This routine accepts a comparison as input and attempts to return a
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comparision that is cheaper to compute.
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*PARG1 and *PARG2 are updated to contain the rtx representing the values
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actually being compared. For example, if *PARG1 was (cc0) and *PARG2
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was (const_int 0), *PARG1 and *PARG2 will be set to the objects that were
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compared to produce cc0.
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On input, *PARG1 and *PARG2 should be set to the first and second
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arguments to the comparison, respectively. CODE is the comparision
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code. For example, if the comparison is:
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The return value is the comparison operator and is either the code of
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A or the code corresponding to the inverse of the comparison. */
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(ne:SI (reg:CC 24 cc)
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(const_int 0 [0x0])))
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The CODE should be NE, *PARG1 should be `(reg:CC 24 cc)' and
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*PARG2 should be `(const_int 0)'.
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Upon return, *PARG1 and and *PARG2 may have new values, indicating
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arguments to a cheaper comparison. *PMODE1 and *PMODE2 will be the
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modes that should be used for those arguments. The return value
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itself will be the comparison code that should be used to compare
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*PARG1 and *PARG2 in order to obtain a value equivalent to that
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given by the original comparison. */
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static enum rtx_code
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find_comparison_args (code, parg1, parg2, pmode1, pmode2)
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@ -3187,30 +3195,38 @@ find_comparison_args (code, parg1, parg2, pmode1, pmode2)
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if (! exp_equiv_p (p->exp, p->exp, 1, 0))
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continue;
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if (GET_CODE (p->exp) == COMPARE
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/* Another possibility is that this machine has a compare insn
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that includes the comparison code. In that case, ARG1 would
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be equivalent to a comparison operation that would set ARG1 to
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either STORE_FLAG_VALUE or zero. If this is an NE operation,
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ORIG_CODE is the actual comparison being done; if it is an EQ,
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we must reverse ORIG_CODE. On machine with a negative value
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for STORE_FLAG_VALUE, also look at LT and GE operations. */
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|| ((code == NE
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|| (code == LT
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&& GET_MODE_CLASS (inner_mode) == MODE_INT
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&& (GET_MODE_BITSIZE (inner_mode)
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<= HOST_BITS_PER_WIDE_INT)
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&& (STORE_FLAG_VALUE
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& ((HOST_WIDE_INT) 1
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<< (GET_MODE_BITSIZE (inner_mode) - 1))))
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/* `(COMPARE A B) != 0)' is equivalent to `(COMPARE A B)'.
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If CODE is EQ, rather than NE, then we are out of luck;
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there is no way to reverse the sense of a COMPARE. */
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if (code == NE && GET_CODE (p->exp) == COMPARE)
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{
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x = p->exp;
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break;
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}
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/* Another possibility is that this machine has a compare
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insn that includes the comparison code. In that case,
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ARG1 would be equivalent to a comparison operation that
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would set ARG1 to either STORE_FLAG_VALUE or zero. If
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this is an NE operation, ORIG_CODE is the actual
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comparison being done; if it is an EQ, we must reverse
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ORIG_CODE. On machine with a negative value for
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STORE_FLAG_VALUE, also look at LT and GE operations. */
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else if ((code == NE
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|| (code == LT
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&& GET_MODE_CLASS (inner_mode) == MODE_INT
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&& (GET_MODE_BITSIZE (inner_mode)
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<= HOST_BITS_PER_WIDE_INT)
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&& (STORE_FLAG_VALUE
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& ((HOST_WIDE_INT) 1
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<< (GET_MODE_BITSIZE (inner_mode) - 1))))
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#ifdef FLOAT_STORE_FLAG_VALUE
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|| (code == LT
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&& GET_MODE_CLASS (inner_mode) == MODE_FLOAT
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&& (REAL_VALUE_NEGATIVE
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(FLOAT_STORE_FLAG_VALUE (GET_MODE (arg1)))))
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|| (code == LT
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&& GET_MODE_CLASS (inner_mode) == MODE_FLOAT
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&& (REAL_VALUE_NEGATIVE
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(FLOAT_STORE_FLAG_VALUE (GET_MODE (arg1)))))
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#endif
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)
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&& GET_RTX_CLASS (GET_CODE (p->exp)) == '<'))
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)
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&& GET_RTX_CLASS (GET_CODE (p->exp)) == '<')
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{
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x = p->exp;
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break;
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@ -5275,8 +5275,16 @@ fold (expr)
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{
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if (TREE_CODE (arg0) == INTEGER_CST)
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{
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if (! TREE_UNSIGNED (type)
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&& TREE_INT_CST_HIGH (arg0) < 0)
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/* If the value is unsigned, then the absolute value is
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the same as the ordinary value. */
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if (TREE_UNSIGNED (type))
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return arg0;
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/* Similarly, if the value is non-negative. */
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else if (INT_CST_LT (integer_minus_one_node, arg0))
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return arg0;
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/* If the value is negative, then the absolute value is
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its negation. */
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else
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{
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unsigned HOST_WIDE_INT low;
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HOST_WIDE_INT high;
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@ -602,7 +602,13 @@ DEFTREECODE (NEGATE_EXPR, "negate_expr", '1', 1)
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DEFTREECODE (MIN_EXPR, "min_expr", '2', 2)
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DEFTREECODE (MAX_EXPR, "max_expr", '2', 2)
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/* Represents the absolute value of the operand.
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An ABS_EXPR must have either an INTEGER_TYPE or a REAL_TYPE. The
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operand of the ABS_EXPR must have the same type. */
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DEFTREECODE (ABS_EXPR, "abs_expr", '1', 1)
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DEFTREECODE (FFS_EXPR, "ffs_expr", '1', 1)
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/* Shift operations for shift and rotate.
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