While fixing bug 21173 and 20963, it was noticed that force_gimple_operand
destroys trees passed to it.
This is a very surprising result, and was the actual underlying cause of those
bugs.
(the testcase in g++.dg/tree-ssa/pr20963.C shows this)
a debugging session:
Breakpoint 3, create_expression_by_pieces (block=0x400c4870,
expr=0x88403f0, stmts=0x400c6510) at tree-ssa-pre.c:1322
expr came from a node in ANTIC_IN, we *can't* modify it, because it's
not a copy.
(gdb) p debug_generic_stmt (expr)
(charD.3 *) &0B->typeD.1681;
...
1388 newexpr = force_gimple_operand (expr,
(gdb) n
1390 if (forced_stmts)
(gdb) p debug_generic_stmt (expr)
(charD.3 *) &D.1708_3->typeD.1681;
--
Summary: force_gimple_operand destroys trees passed to it
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dberlin at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21236
