[PATCH 2/4] simplify OP_COMPUTEDGOTO with unique and known target

[Luc Van Oostenryck <luc.vanoostenryck@gmail.com>]

If the OP_COMPUTEDGOTO's source pseudo is defined by a single
OP_SETVAL/EXPR_LABEL, then the corresponding basic block is the
only possible destination and the computed goto can then be
simplified into a simple branch.

So, convert such computed goto into a simple OP_BR which may
then participate in other flow simplifications.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 simplify.c                 | 30 ++++++++++++++++++++++++++++++
 validation/optim/cgoto01.c |  1 -
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/simplify.c b/simplify.c
index e58fb6cf3941..132d408f59f1 100644
--- a/simplify.c
+++ b/simplify.c
@@ -2112,6 +2112,34 @@ found:
 	return REPEAT_CSE;
 }
 
+static int simplify_cgoto(struct instruction *insn)
+{
+	struct basic_block *target, *bb = insn->bb;
+	struct instruction *def;
+	struct multijmp *jmp;
+
+	switch (DEF_OPCODE(def, insn->src)) {
+	case OP_SETVAL:
+		if (def->val->type != EXPR_LABEL)
+			break;
+		target = def->val->symbol->bb_target;
+		if (!target->ep)
+			return 0;
+		FOR_EACH_PTR(insn->multijmp_list, jmp) {
+			if (jmp->target == target)
+				continue;
+			remove_bb_from_list(&jmp->target->parents, bb, 1);
+			remove_bb_from_list(&bb->children, jmp->target, 1);
+			MARK_CURRENT_DELETED(jmp);
+		} END_FOR_EACH_PTR(jmp);
+		kill_use(&insn->src);
+		insn->opcode = OP_BR;
+		insn->bb_true = target;
+		return REPEAT_CSE|REPEAT_CFG_CLEANUP;
+	}
+	return 0;
+}
+
 int simplify_instruction(struct instruction *insn)
 {
 	unsigned flags;
@@ -2190,6 +2218,8 @@ int simplify_instruction(struct instruction *insn)
 		return simplify_branch(insn);
 	case OP_SWITCH:
 		return simplify_switch(insn);
+	case OP_COMPUTEDGOTO:
+		return simplify_cgoto(insn);
 	case OP_RANGE:
 		return simplify_range(insn);
 	case OP_FADD:
diff --git a/validation/optim/cgoto01.c b/validation/optim/cgoto01.c
index 350c6cd99f08..94b2c2c429db 100644
--- a/validation/optim/cgoto01.c
+++ b/validation/optim/cgoto01.c
@@ -16,7 +16,6 @@ L2:	abort();
 /*
  * check-name: cgoto01
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-excludes: set\\.
-- 
2.29.2