The following patch fixes PR57134 by
a) excluding bitfield expansion when EXPAND_MEMORY, and
b) passing down the EXPAND_MEMORY modifier in a couple of places where
this does not currently happen on recursive calls to expand_expr().
(a) has precedent elsewhere in expr.c, eg. see expand_expr_real_1
<MEM_REF>, (b) is a little difficult to justify except to claim
there's no logical reason why it should be excluded nowadays. Hand
waving argument follows:
Of the seven expand_expr() modifiers, recursive calls made to handle
inner references of aggregate types currently exclude EXPAND_SUM,
EXPAND_WRITE, and EXPAND_MEMORY from the modifier passed. I suppose
EXPAND_SUM is excluded so that the inner expand_expr() won't return a
PLUS or MULT when we might be adding a further offset, but I can't see
why the other two modifiers are not passed. Digging through the
history, it looks like EXPAND_WRITE may have been missed by accident,
and EXPAND_MEMORY used to be an entirely different animal. kenner was
responsible for the original recursive call that passed down
EXPAND_NORMAL, EXPAND_CONST_ADDRESS and EXPAND_INITIALIZER when expr.h
looked like:
14612 kenner EXPAND_MEMORY_USE_* are explained below. */
406 kenner enum expand_modifier {EXPAND_NORMAL, EXPAND_SUM,
14612 kenner EXPAND_CONST_ADDRESS, EXPAND_INITIALIZER,
14612 kenner EXPAND_MEMORY_USE_WO,
EXPAND_MEMORY_USE_RW,
14612 kenner EXPAND_MEMORY_USE_BAD,
EXPAND_MEMORY_USE_DONT};
406 kenner
14612 kenner /* Argument for chkr_* functions.
14612 kenner MEMORY_USE_RO: the pointer reads memory.
14612 kenner MEMORY_USE_WO: the pointer writes to memory.
14612 kenner MEMORY_USE_RW: the pointer modifies memory (ie it reads
and writes). An
14612 kenner example is (*ptr)++
14612 kenner MEMORY_USE_BAD: use this if you don't know the behavior of
the pointer, or
14612 kenner if you know there are no pointers. Using
an INDIRECT_REF
14612 kenner with MEMORY_USE_BAD will abort.
14612 kenner MEMORY_USE_TW: just test for writing, without update.
Special.
14612 kenner MEMORY_USE_DONT: the memory is neither read nor written.
This is used by
14612 kenner '->' and '.'. */
So I think passing EXPAND_MEMORY and EXPAND_WRITE down ought to be
good. The VIEW_CONVERT_EXPR case really doesn't need to exclude
EXPAND_SUM either, since it doesn't allow an offset, but I made it the
same as the inner ref case so that when/if someone attends to
/* ??? We should work harder and deal with non-zero offsets. */
it doesn't cause a surprise. Really, a lot of this code needs
attention, for example, I think SSA made EXPAND_STACK_PARM and all of
the related code in calls.c dealing with libcalls when expanding args,
unnecessary.
Bootstrapped and regression tested powerpc64-linux. OK to apply?
PR middle-end/57134
* expr.c (expand_expr_real_1 <normal_inner_ref>): Pass
EXPAND_MEMORY and EXPAND_WRITE to recursive call. Don't use
bitfield expansion when EXPAND_MEMORY.
(expand_expr_real_1 <VIEW_CONVERT_EXPR>): Pass modifier likewise.
Index: gcc/expr.c
===================================================================
--- gcc/expr.c (revision 199940)
+++ gcc/expr.c (working copy)
@@ -9918,12 +9919,8 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
&& modifier != EXPAND_STACK_PARM
? target : NULL_RTX),
VOIDmode,
- (modifier == EXPAND_INITIALIZER
- || modifier == EXPAND_CONST_ADDRESS
- || modifier == EXPAND_STACK_PARM)
- ? modifier : EXPAND_NORMAL);
+ modifier == EXPAND_SUM ? EXPAND_NORMAL : modifier);
-
/* If the bitfield is volatile, we want to access it in the
field's mode, not the computed mode.
If a MEM has VOIDmode (external with incomplete type),
@@ -10081,6 +10078,7 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
|| (MEM_P (op0)
&& (MEM_ALIGN (op0) < GET_MODE_ALIGNMENT (mode1)
|| (bitpos % GET_MODE_ALIGNMENT (mode1) != 0))))
+ && modifier != EXPAND_MEMORY
&& ((modifier == EXPAND_CONST_ADDRESS
|| modifier == EXPAND_INITIALIZER)
? STRICT_ALIGNMENT
@@ -10279,10 +10277,7 @@ expand_expr_real_1 (tree exp, rtx target, enum mac
&& modifier != EXPAND_STACK_PARM
? target : NULL_RTX),
VOIDmode,
- (modifier == EXPAND_INITIALIZER
- || modifier == EXPAND_CONST_ADDRESS
- || modifier == EXPAND_STACK_PARM)
- ? modifier : EXPAND_NORMAL);
+ modifier == EXPAND_SUM ? EXPAND_NORMAL : modifier);
if (MEM_P (orig_op0))
{
--
Alan Modra
Australia Development Lab, IBM
