===================================================================
@@ -346,8 +346,11 @@ tree_forwarder_block_p (basic_block bb,
if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun) || (e->flags & EDGE_EH))
return false;
/* If goto_locus of any of the edges differs, prevent removing
- the forwarder block for -O0. */
- else if (optimize == 0 && e->goto_locus != locus)
+ the forwarder block when not optimizing. */
+ else if (!optimize
+ && (LOCATION_LOCUS (e->goto_locus) != UNKNOWN_LOCATION
+ || LOCATION_LOCUS (locus) != UNKNOWN_LOCATION)
+ && e->goto_locus != locus)
return false;
}
@@ -362,7 +365,10 @@ tree_forwarder_block_p (basic_block bb,
case GIMPLE_LABEL:
if (DECL_NONLOCAL (gimple_label_label (as_a <glabel *> (stmt))))
return false;
- if (optimize == 0 && gimple_location (stmt) != locus)
+ if (!optimize
+ && (gimple_has_location (stmt)
+ || LOCATION_LOCUS (locus) != UNKNOWN_LOCATION)
+ && gimple_location (stmt) != locus)
return false;
break;
As explained in the audit trail, the goal of the fix for PR debug/44205: * tree-cfgcleanup.c (tree_forwarder_block_p): Return false if at -O0 goto_locus of any of the incoming edges differs from goto_locus of outgoing edge, or gimple_location of any of the labels differs. was to enable the bypassing of forwarder blocks at -O0 when the locus on the edges to be threaded represent both either UNKNOWN_LOCATION or the same location. It was made for GCC 4.6 and below when the locus value represented only the location information so a simple locus comparison was used. Since then the locus value was changed and represents now a combination of location information and block information. This means that you can have 2 locus representing both UNKNOWN_LOCATION but with different values and the change disabled the bypassing of forwarder blocks in this case. The attached patch reenables it, i.e. when the locus on the edges represent both UNKNOWN_LOCATION. The idiom is already used at the RTL level e.g. in try_forward_edges. That's quite effective in Ada to remove dead branches generated for size computations of variable-sized types at -O0. Tested (GCC and GDB) on x86-64/Linux, applied on the mainline as obvious. 2018-06-19 Eric Botcazou <ebotcazou@adacore.com> * tree-cfgcleanup.c (tree_forwarder_block_p): Do not return false at -O0 if the locus represent UNKNOWN_LOCATION but have different values.