fix add_join_conditional() one of the alternative is VOID

Commit Message

Luc Van Oostenryck Jan. 29, 2021, 12:28 a.m. UTC

add_join_conditional()'s job is to take the 2 alternatives
of the conditional, make a phi-node from them and return
the corresponding pseudo but if one of the alternatives
is not available it's useless to create a phi-node and
the other alternative can then directly be returned.

The problem is that in this later case, the pseudo directly
returned is the PSEUDO_PHI of the corresponding phi-source.
This gives erroneous code like, for example:
	phisrc.32	%phi1 <- $0
	ret.32		%phi1
instead of:
	ret.32		$0
since the %ph1 should only be used by a phi-node instruction.

Fix this by returning phi-source's operand instead.

Signed-off-by: Luc Van Oostenryck <[e-mail]>
---
 linearize.c                           |  4 ++--
 validation/linear/join-cond-discard.c | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 validation/linear/join-cond-discard.c

Patch

diff --git a/linearize.c b/linearize.c
index e80715ab2458..7a6f745fd4fc 100644
--- a/linearize.c
+++ b/linearize.c
@@ -1678,9 +1678,9 @@  static pseudo_t add_join_conditional(struct entrypoint *ep, struct expression *e
 	struct instruction *phi_node;
 
 	if (phi1 == VOID)
-		return phi2;
+		return (phi2 == VOID) ? phi2 : phi2->def->src;
 	if (phi2 == VOID)
-		return phi1;
+		return (phi1 == VOID) ? phi1 : phi1->def->src;
 
 	phi_node = alloc_typed_instruction(OP_PHI, expr->ctype);
 	use_pseudo(phi_node, phi1, add_pseudo(&phi_node->phi_list, phi1));
diff --git a/validation/linear/join-cond-discard.c b/validation/linear/join-cond-discard.c
new file mode 100644
index 000000000000..9f07a7d499f6
--- /dev/null
+++ b/validation/linear/join-cond-discard.c
@@ -0,0 +1,19 @@ 
+void abort(void) __attribute__((noreturn));
+
+int bar(int a)
+{
+	return a ? (abort(), 0) : 0;
+}
+
+int qux(int a)
+{
+	return a ? (abort(), 0) : (abort(), 1);
+}
+
+/*
+ * check-name: join-cond-discard
+ * check-command: test-linearize -Wno-decl $file
+ *
+ * check-output-ignore
+ * check-output-excludes: phisrc\\..*phi
+ */