3 files changed, 43 insertions, 0 deletions
diff --git a/simplify.c b/simplify.c
index 6ab9f622..47ec780c 100644
--- a/simplify.c
+++ b/simplify.c
@@ -337,6 +337,21 @@ static int simplify_asr(struct instruction *insn, pseudo_t pseudo, long long val
 	return 0;
 }
 
+static int simplify_mul_div(struct instruction *insn, long long value)
+{
+	if (value == 1)
+		return replace_with_pseudo(insn, insn->src1);
+
+	switch (insn->opcode) {
+	case OP_MULS:
+	case OP_MULU:
+		if (value == 0)
+			return replace_with_pseudo(insn, insn->src2);
+	}
+
+	return 0;
+}
+
 static int simplify_constant_rightside(struct instruction *insn)
 {
 	long long value = insn->src2->value;
@@ -361,6 +376,8 @@ static int simplify_constant_rightside(struct instruction *insn)
 		return simplify_asr(insn, insn->src1, value);
 
 	case OP_MULU: case OP_MULS:
+		return simplify_mul_div(insn, value);
+
 	case OP_AND_BOOL:
 		if (value == 1)
 			return replace_with_pseudo(insn, insn->src1);
diff --git a/validation/optim/muldiv-by-one.c b/validation/optim/muldiv-by-one.c
new file mode 100644
index 00000000..ac8ac95b
--- /dev/null
+++ b/validation/optim/muldiv-by-one.c
@@ -0,0 +1,13 @@
+typedef	unsigned int ui;
+typedef	         int si;
+
+si smul1(si a) {  return a * 1; }
+ui umul1(ui a) {  return a * 1; }
+
+/*
+ * check-name: muldiv-by-one
+ * check-command: test-linearize -Wno-decl $file
+ * check-output-ignore
+ *
+ * check-output-excludes: mul[us]\\.
+ */
diff --git a/validation/optim/muldiv-by-zero.c b/validation/optim/muldiv-by-zero.c
new file mode 100644
index 00000000..07b7b1a7
--- /dev/null
+++ b/validation/optim/muldiv-by-zero.c
@@ -0,0 +1,13 @@
+typedef	unsigned int ui;
+typedef	         int si;
+
+si smul0(si a) {  return a * 0; }
+ui umul0(ui a) {  return a * 0; }
+
+/*
+ * check-name: muldiv-by-zero
+ * check-command: test-linearize -Wno-decl $file
+ * check-output-ignore
+ *
+ * check-output-excludes: mul[us]\\.
+ */