Hi!
With the PR54519 patch I've just posted, I've noticed, I've noticed on the
same testcase from yesterday's IRC:
static inline void foo (int x, int y) { asm volatile ("nop"); }
static inline void bar (int z) { foo (z, 0); foo (z, 1); }
int main ()
{
bar (0);
bar (1);
return 0;
}
that while I can print x and y just fine, if I do bt, x, y and z printed
in the backtrace are all optimized out.
The problem is that first tree versioning for foo.isra.* or bar.isra.*
deposits the optimized away parameters as VAR_DECLs into the DECL_INITIAL
block (which is fine), but then during inlining they end up in the remapped
block of DECL_INITIAL, not the new block added above it into which inliner
puts parameters. So in the debug info we have
DW_TAG_inlined_subroutine
DW_TAG_formal_parameter for non-optimized away parameters
DW_TAG_lexical_block
DW_TAG_formal_parameter for optimized away parameters
and the debugger (expectably) looks only at DW_TAG_inlined_subroutine
DIE's immediate children for the formal parameters to print during
backtrace.
Fixed up by moving the VAR_DECLs for parameters optimized away by versioning
to BLOCK_SUPERCONTEXT during inlining, at that point we know both of the
blocks have the same scope, and if the original DECL_INITIAL doesn't contain
any other vars, we can actually end up with shorter/more correct debug info
as well as memory savings due to being able to GC the remapped DECL_INITIAL
block.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-10-03 Jakub Jelinek <ja...@redhat.com>
* tree-inline.c (expand_call_inline): Move VAR_DECLs with
PARM_DECL origins from remapped DECL_INITIAL's BLOCK_VARS
into id->block's BLOCK_VARS.
--- gcc/tree-inline.c.jj 2012-10-02 17:43:13.000000000 +0200
+++ gcc/tree-inline.c 2012-10-02 19:43:52.576382413 +0200
@@ -3946,7 +3946,29 @@ expand_call_inline (basic_block bb, gimp
initialize_inlined_parameters (id, stmt, fn, bb);
if (DECL_INITIAL (fn))
- prepend_lexical_block (id->block, remap_blocks (DECL_INITIAL (fn), id));
+ {
+ tree *var;
+
+ prepend_lexical_block (id->block, remap_blocks (DECL_INITIAL (fn), id));
+ gcc_checking_assert (BLOCK_SUBBLOCKS (id->block)
+ && (BLOCK_CHAIN (BLOCK_SUBBLOCKS (id->block))
+ == NULL_TREE));
+ /* Move vars for PARM_DECLs from DECL_INITIAL block to id->block,
+ otherwise DW_TAG_formal_parameter will not be children of
+ DW_TAG_inlined_subroutine, but of a DW_TAG_lexical_block
+ under it. The parameters can be then evaluated in the debugger,
+ but don't show in backtraces. */
+ for (var = &BLOCK_VARS (BLOCK_SUBBLOCKS (id->block)); *var; )
+ if (TREE_CODE (DECL_ORIGIN (*var)) == PARM_DECL)
+ {
+ tree v = *var;
+ *var = TREE_CHAIN (v);
+ TREE_CHAIN (v) = BLOCK_VARS (id->block);
+ BLOCK_VARS (id->block) = v;
+ }
+ else
+ var = &TREE_CHAIN (*var);
+ }
/* Return statements in the function body will be replaced by jumps
to the RET_LABEL. */
Jakub
