aboutsummaryrefslogtreecommitdiff
path: root/gcc/PROBLEMS
diff options
context:
space:
mode:
Diffstat (limited to 'gcc/PROBLEMS')
-rw-r--r--gcc/PROBLEMS117
1 files changed, 0 insertions, 117 deletions
diff --git a/gcc/PROBLEMS b/gcc/PROBLEMS
deleted file mode 100644
index bc532e641a8..00000000000
--- a/gcc/PROBLEMS
+++ /dev/null
@@ -1,117 +0,0 @@
-3. When find_reloads is used to count number of spills needed
-it does not take into account the fact that a reload may
-turn out to be a dummy.
-
-I'm not sure this really happens any more. Doesn't it find
-all the dummies on both passes?
-
-10. movl a3@,a0
- movl a3@(16),a1
- clrb a0@(a1:l)
-is generated and may be worse than
- movl a3@,a0
- addl a3@(16),a0
- clrb a0@
-If ordering of operands is improved, many more
-such cases will be generated from typical array accesses.
-
-38. Hack expand_mult so that if there is no same-modes multiply
-it will use a widening multiply and then truncate rather than
-calling the library.
-
-39. Hack expanding of division to notice cases for
-long -> short division.
-
-40. Represent divide insns as (DIV:SI ...) followed by
-a separate lowpart extract. Represent remainder insns as DIV:SI
-followed by a separate highpart extract. Then cse can work on
-the DIV:SI part. Problem is, this may not be desirable on machines
-where computing the quotient alone does not necessarily give
-a remainder--such as the 68020 for long operands.
-
-52. Reloading can look at how reload_contents got set up.
-If it was copied from a register, just reload from that register.
-Otherwise, perhaps can change the previous insn to move the
-data via the reload reg, thus avoiding one memory ref.
-
-63. Potential problem in cc_status.value2, if it ever activates itself
-after a two-address subtraction (which currently cannot happen).
-It is supposed to compare the current value of the destination
-but eliminating it would use the results of the subtraction, equivalent
-to comparing the previous value of the destination.
-
-65. Should loops that neither start nor end with a break
-be rearranged to end with the last break?
-
-69. Define the floating point converting arithmetic instructions
-for the 68881.
-
-74. Combine loop opt with cse opt in one pass. Do cse on each loop,
-then loop opt on that loop, and go from innermost loops outward.
-Make loop invariants available for cse at end of loop.
-
-85. pea can force a value to be reloaded into an areg
-which can make it worse than separate adding and pushing.
-This can only happen for adding something within addql range
-and it only loses if the qty becomes dead at that point
-so it can be added to with no copying.
-
-93. If a pseudo doesn't get a hard reg everywhere,
-can it get one during a loop?
-
-96. Can do SImode bitfield insns without reloading, but must
-alter the operands in special ways.
-
-99. final could check loop-entry branches to see if they
-screw up deletion of a test instruction. If they do,
-can put another test instruction before the branch and
-make it conditional and redirect it.
-
-106. Aliasing may be impossible if data types of refs differ
-and data type of containing objects also differ.
-(But check this wrt unions.)
-
-108. Can speed up flow analysis by making a table saying which
-register is set and which registers are used by each instruction that
-only sets one register and only uses two. This way avoid the tree
-walk for such instructions (most instructions).
-
-109. It is desirable to avoid converting INDEX to SImode if a
-narrower mode suffices, as HImode does on the 68000.
-How can this be done?
-
-110. Possible special combination pattern:
-If the two operands to a comparison die there and both come from insns
-that are identical except for replacing one operand with the other,
-throw away those insns. Ok if insns being discarded are known 1 to 1.
-An andl #1 after a seq is 1 to 1, but how should compiler know that?
-
-112. Can convert float to unsigned int by subtracting a constant,
-converting to signed int, and changing the sign bit.
-
-117. Any number of slow zero-extensions in one loop, that have
-their clr insns moved out of the loop, can share one register
-if their original life spans are disjoint.
-But it may be hard to be sure of this since
-the life span data that regscan produces may be hard to interpret
-validly or may be incorrect after cse.
-
-118. In cse, when a bfext insn refers to a register, if the field
-corresponds to a halfword or a byte and the register is equivalent
-to a memory location, it would be possible to detect this and
-replace it with a simple memory reference.
-
-121. Insns that store two values cannot be moved out of loops.
-The code in scan_loop doesn't even try to deal with them.
-
-122. When insn-output.c turns a bit-test into a sign-test,
-it should see whether the cc is already set up with that sign.
-
-123. When a conditional expression is used as a function arg, it would
-be faster (and in some cases shorter) to push each alternative rather
-than compute in a register and push that. This would require
-being able to specify "push this" as a target for expand_expr.
-
-124. On the 386, bad code results from foo (bar ()) when bar
-returns a double, because the pseudo used fails to get preferenced
-into an fp reg because of the distinction between regs 8 and 9.