OP_CALL were ignored by kill_instruction() but there are two cases
were something can or must be done:
1) if the function is pure, it is free of side-effects and can thus
be optimized away like others instructions.
2) if force-killed then we need to adjust the usage of all the arguments.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 11 +++++++++++
validation/kill-pure-call.c | 17 +++++++++++++++++
2 files changed, 28 insertions(+)
create mode 100644 validation/kill-pure-call.c
diff --git a/simplify.c b/simplify.c
index b8944f0f7..cacf81f9f 100644
--- a/simplify.c
+++ b/simplify.c
@@ -236,6 +236,17 @@ void kill_insn(struct instruction *insn, int force)
kill_use(&insn->cond);
break;
+ case OP_CALL:
+ if (!force) {
+ /* a "pure" function can be killed too */
+ if (!(insn->func->type == PSEUDO_SYM))
+ return;
+ if (!(insn->func->sym->ctype.modifiers & MOD_PURE))
+ return;
+ }
+ kill_use_list(insn->arguments);
+ break;
+
case OP_ENTRY:
/* ignore */
return;
diff --git a/validation/kill-pure-call.c b/validation/kill-pure-call.c
new file mode 100644
index 000000000..d3f78c026
--- /dev/null
+++ b/validation/kill-pure-call.c
@@ -0,0 +1,17 @@
+int side(int a);
+int pure(int a) __attribute__((pure));
+
+int keep(int a) { return side(a) && 0; }
+int kill(int a) { return pure(a) && 0; }
+
+/*
+ * check-name: kill-pure-call
+ * check-command: test-linearize -Wno-decl $file
+ * check-description:
+ * See that the call is optimized away but only
+ * when the function is "pure".
+ *
+ * check-output-ignore
+ * check-output-contains: call\\..* side
+ * check-output-excludes: call\\..* pure
+ */
--
2.11.0
--
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