insert_branch() is called after an optimization has detected an opportunity to convert a switch or a conditional branch into an unconditional branch (for example because the condition is a constant). It does this by removing the BB's last instruction and then allocate a new unconditional branch which is added at the end of the BB. The old instruction is simply discarded. Since the discarded instruction is one with a condition we must insure that the associated usage is also removed (for example, by calling kill_instruction()). But currently kill_instruction() is called, just after the call to insert_branch(), only at a single place. The 4 other places where insert_branch() is called do nothing with the removed instruction and it's condition's usage. As consequence, instructions that are dead are not removed since it still wrongly has an user. Fix this by adding a call to kill_instruction() in insert_branch() itself (and make the function description more exact). Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> --- flow.c | 1 - linearize.c | 3 ++- validation/kill-insert-branch.c | 22 ++++++++++++++++++++++ 3 files changed, 24 insertions(+), 2 deletions(-) create mode 100644 validation/kill-insert-branch.c diff --git a/flow.c b/flow.c index 09c9b8075..20031a9d5 100644 --- a/flow.c +++ b/flow.c @@ -226,7 +226,6 @@ try_to_rewrite_target: if (bb_list_size(target->parents) != 1) return retval; insert_branch(target, insn, final); - kill_instruction(insn); return 1; } diff --git a/linearize.c b/linearize.c index a36ab48c3..889483d28 100644 --- a/linearize.c +++ b/linearize.c @@ -646,7 +646,7 @@ static void remove_parent(struct basic_block *child, struct basic_block *parent) repeat_phase |= REPEAT_CFG_CLEANUP; } -/* Change a "switch" into a branch */ +/* Change a "switch" or a conditional branch into a branch */ void insert_branch(struct basic_block *bb, struct instruction *jmp, struct basic_block *target) { struct instruction *br, *old; @@ -655,6 +655,7 @@ void insert_branch(struct basic_block *bb, struct instruction *jmp, struct basic /* Remove the switch */ old = delete_last_instruction(&bb->insns); assert(old == jmp); + kill_instruction(old); br = alloc_instruction(OP_BR, 0); br->bb = bb; diff --git a/validation/kill-insert-branch.c b/validation/kill-insert-branch.c new file mode 100644 index 000000000..e59b5bbcd --- /dev/null +++ b/validation/kill-insert-branch.c @@ -0,0 +1,22 @@ +void foo(int a) +{ + int b = 1; + if (a) + b++; + if (b) + ; +} + +void bar(int a) +{ + if (a ? 1 : 2) + ; +} + +/* + * check-name: kill insert-branch + * check-command: test-linearize -Wno-decl $file + * + * check-output-ignore + * check-output-excludes: select\\. + */ -- 2.12.2 -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html