12 files changed, 102 insertions, 11 deletions
diff --git a/flow.c b/flow.c
index f052cdb1..2e20ab75 100644
--- a/flow.c
+++ b/flow.c
@@ -121,6 +121,31 @@ static int bb_depends_on_phi(struct basic_block *target, struct basic_block *src
 	return 0;
 }
 
+///
+// does the BB contains ignorable instructions but a final branch?
+// :note: something could be done for phi-sources but ... we'll see.
+static bool bb_is_forwarder(struct basic_block *bb)
+{
+	struct instruction *insn;
+
+	FOR_EACH_PTR(bb->insns, insn) {
+		if (!insn->bb)
+			continue;
+		switch (insn->opcode) {
+		case OP_NOP:
+		case OP_INLINED_CALL:
+			continue;
+		case OP_CBR:
+		case OP_BR:
+			return true;
+		default:
+			goto out;
+		}
+	} END_FOR_EACH_PTR(insn);
+out:
+	return false;
+}
+
 /*
  * When we reach here, we have:
  *  - a basic block that ends in a conditional branch and
@@ -742,6 +767,22 @@ void vrfy_flow(struct entrypoint *ep)
 	assert(!entry);
 }
 
+static int retarget_parents(struct basic_block *bb, struct basic_block *target)
+{
+	struct basic_block *parent;
+
+	/*
+	 * We can't do FOR_EACH_PTR() here, because the parent list
+	 * may change when we rewrite the parent.
+	 */
+	while ((parent = first_basic_block(bb->parents))) {
+		if (!rewrite_parent_branch(parent, bb, target))
+			return 0;
+	}
+	kill_bb(bb);
+	return REPEAT_CFG_CLEANUP;
+}
+
 static void remove_merging_phisrc(struct basic_block *top, struct instruction *insn)
 {
 	struct instruction *user = get_phinode(insn);
@@ -821,6 +862,43 @@ static int merge_bb(struct basic_block *top, struct basic_block *bot)
 	return REPEAT_CFG_CLEANUP;
 }
 
+///
+// early simplification of the CFG
+// Three things are done here:
+//    # inactive BB are removed
+//    # branches to a 'forwarder' BB are redirected to the forwardee.
+//    # merge single-child/single-parent BBs.
+int simplify_cfg_early(struct entrypoint *ep)
+{
+	struct basic_block *bb;
+	int changed = 0;
+
+	FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
+		struct instruction *insn;
+		struct basic_block *tgt;
+
+		if (!bb->ep) {
+			DELETE_CURRENT_PTR(bb);
+			changed = REPEAT_CFG_CLEANUP;
+			continue;
+		}
+
+		insn = last_instruction(bb->insns);
+		if (!insn)
+			continue;
+		switch (insn->opcode) {
+		case OP_BR:
+			tgt = insn->bb_true;
+			if (bb_is_forwarder(bb))
+				changed |= retarget_parents(bb, tgt);
+			else if (bb_list_size(tgt->parents) == 1)
+				changed |= merge_bb(bb, tgt);
+			break;
+		}
+	} END_FOR_EACH_PTR_REVERSE(bb);
+	return changed;
+}
+
 void pack_basic_blocks(struct entrypoint *ep)
 {
 	struct basic_block *bb;
diff --git a/flow.h b/flow.h
index 099767d4..19a743c8 100644
--- a/flow.h
+++ b/flow.h
@@ -18,6 +18,7 @@ extern void kill_dead_stores(struct entrypoint *ep, pseudo_t addr, int local);
 extern void simplify_symbol_usage(struct entrypoint *ep);
 extern void simplify_memops(struct entrypoint *ep);
 extern void pack_basic_blocks(struct entrypoint *ep);
+extern int simplify_cfg_early(struct entrypoint *ep);
 
 extern void convert_instruction_target(struct instruction *insn, pseudo_t src);
 extern void remove_dead_insns(struct entrypoint *);
diff --git a/optimize.c b/optimize.c
index 8ab105bc..338714c7 100644
--- a/optimize.c
+++ b/optimize.c
@@ -57,6 +57,11 @@ void optimize(struct entrypoint *ep)
 	kill_unreachable_bbs(ep);
 	ir_validate(ep);
 
+	cfg_postorder(ep);
+	if (simplify_cfg_early(ep))
+		kill_unreachable_bbs(ep);
+	ir_validate(ep);
+
 	domtree_build(ep);
 
 	/*
diff --git a/validation/call-inlined.c b/validation/call-inlined.c
index 3612c5c4..a6cb4b5b 100644
--- a/validation/call-inlined.c
+++ b/validation/call-inlined.c
@@ -28,12 +28,14 @@ foo:
 	<entry-point>
 	add.32      %r3 <- %arg1, %arg2
 	add.32      %r5 <- %r3, $1
+	# call      %r6 <- add, %r3, $1
 	ret.32      %r5
 
 
 bar:
 .L3:
 	<entry-point>
+	# call      %r13 <- add, %r10, $1
 	ret
 
 
@@ -41,6 +43,7 @@ bas:
 .L6:
 	<entry-point>
 	add.64      %r16 <- "abc", $1
+	# call      %r17 <- lstrip, %r14
 	ret.64      %r16
 
 
@@ -48,6 +51,7 @@ qus:
 .L9:
 	<entry-point>
 	add.64      %r21 <- messg, $1
+	# call      %r22 <- lstrip, %r19
 	ret.64      %r21
 
 
diff --git a/validation/expand/builtin_constant_inline0.c b/validation/expand/builtin_constant_inline0.c
index a0057f20..d72a211f 100644
--- a/validation/expand/builtin_constant_inline0.c
+++ b/validation/expand/builtin_constant_inline0.c
@@ -16,6 +16,7 @@ int foo(void)
 foo:
 .L0:
 	<entry-point>
+	# call      %r1 <- is_const, $42
 	ret.32      $42
 
 
diff --git a/validation/inline_base0.c b/validation/inline_base0.c
index 517ee972..698c760f 100644
--- a/validation/inline_base0.c
+++ b/validation/inline_base0.c
@@ -27,6 +27,7 @@ foo0:
 .L0:
 	<entry-point>
 	add.32      %r5 <- %arg1, %arg2
+	# call      %r6 <- add, %r1, %r2
 	ret.32      %r5
 
 
@@ -34,12 +35,14 @@ foo1:
 .L3:
 	<entry-point>
 	add.32      %r10 <- %arg1, $1
+	# call      %r11 <- add, %r8, $1
 	ret.32      %r10
 
 
 foo2:
 .L6:
 	<entry-point>
+	# call      %r13 <- add, $1, $2
 	ret.32      $3
 
 
diff --git a/validation/linear/builtin_unreachable0.c b/validation/linear/builtin_unreachable0.c
index 911ed7f9..4fc56473 100644
--- a/validation/linear/builtin_unreachable0.c
+++ b/validation/linear/builtin_unreachable0.c
@@ -14,12 +14,12 @@ foo:
 .L0:
 	<entry-point>
 	seteq.32    %r2 <- %arg1, $3
-	cbr         %r2, .L1, .L3
+	cbr         %r2, .L1, .L2
 
 .L1:
 	unreachable
 
-.L3:
+.L2:
 	ret.32      %arg1
 
 
diff --git a/validation/linear/builtin_unreachable1.c b/validation/linear/builtin_unreachable1.c
index 70f6674c..2fc1d728 100644
--- a/validation/linear/builtin_unreachable1.c
+++ b/validation/linear/builtin_unreachable1.c
@@ -16,9 +16,9 @@ int foo(int c)
 foo:
 .L0:
 	<entry-point>
-	cbr         %arg1, .L3, .L2
+	cbr         %arg1, .L1, .L2
 
-.L3:
+.L1:
 	ret.32      $1
 
 .L2:
diff --git a/validation/linear/call-inline.c b/validation/linear/call-inline.c
index dfd49b62..1ad785ee 100644
--- a/validation/linear/call-inline.c
+++ b/validation/linear/call-inline.c
@@ -13,6 +13,6 @@ int i3(void) { return (***fun)(); }		// C99,C11 6.5.3.2p4
  *
  * check-output-ignore
  * check-output-excludes: load
- * check-output-excludes: call
+ * check-output-excludes: \\tcall
  * check-output-pattern(5): ret\\..* \\$42
  */
diff --git a/validation/mem2reg/cond-expr.c b/validation/mem2reg/cond-expr.c
index 8acb00ac..2474d65d 100644
--- a/validation/mem2reg/cond-expr.c
+++ b/validation/mem2reg/cond-expr.c
@@ -9,6 +9,6 @@ int foo(int a, int b, int c)
  * check-name: cond-expr
  * check-command: test-linearize -Wno-decl -fdump-ir=mem2reg $file
  * check-output-ignore
- * check-output-pattern(2): phi\\.
- * check-output-pattern(3): phisrc\\.
+ * check-output-pattern(1): phi\\.
+ * check-output-pattern(2): phisrc\\.
  */
diff --git a/validation/mem2reg/cond-expr5.c b/validation/mem2reg/cond-expr5.c
index a3ce5e3a..beef8f25 100644
--- a/validation/mem2reg/cond-expr5.c
+++ b/validation/mem2reg/cond-expr5.c
@@ -15,7 +15,6 @@ int foo(int p, int q, int a)
  * check-output-ignore
  * check-output-excludes: load\\.
  * check-output-excludes: store\\.
- * check-output-excludes: phi\\..*, .*, .*
- * check-output-pattern(3): phi\\.
- * check-output-pattern(5): phisrc\\.
+ * check-output-pattern(2): phi\\.
+ * check-output-pattern(4): phisrc\\.
  */
diff --git a/validation/optim/cse-size.c b/validation/optim/cse-size.c
index e1a5d492..0c0c2d14 100644
--- a/validation/optim/cse-size.c
+++ b/validation/optim/cse-size.c
@@ -13,6 +13,6 @@ static void foo(void)
  * check-command: test-linearize -Wno-decl $file
  *
  * check-output-ignore
- * check-output-pattern(0,1): phi\\.
+ * check-output-excludes: phi\\.
  * check-output-excludes: cbr
  */