@@ -312,6 +312,9 @@ static int simplify_asr(struct instruction *insn, pseudo_t pseudo, long long val
static int simplify_mul_div(struct instruction *insn, long long value)
{
+ unsigned long long sbit = 1ULL << (insn->size - 1);
+ unsigned long long bits = sbit | (sbit - 1);
+
if (value == 1)
return replace_with_pseudo(insn, insn->src1);
@@ -320,6 +323,15 @@ static int simplify_mul_div(struct instruction *insn, long long value)
case OP_MULU:
if (value == 0)
return replace_with_pseudo(insn, insn->src2);
+
+ if (!(value & sbit)) // positive
+ break;
+
+ value |= ~bits;
+ if (value == -1) {
+ insn->opcode = OP_NEG;
+ return REPEAT_CSE;
+ }
/* Fall through */
case OP_DIVS:
case OP_DIVU:
new file mode 100644
@@ -0,0 +1,13 @@
+typedef unsigned int u32;
+
+int smulm1(int a) { return a * -1; }
+u32 umulm1(u32 a) { return a * (u32) -1; }
+
+/*
+ * check-name: muldiv-minus-one
+ * check-command: test-linearize -Wno-decl $file
+ * check-output-ignore
+ *
+ * check-output-excludes: mul[us]\\.
+ * check-output-contains: neg\\.
+ */
Currently we simplify multiplication by 1 but nothing is done for multiplication by -1 which is equivalent to the negation of its first operand. This patch add this simplification. Also add small test cases showing the simplification. Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> --- simplify.c | 12 ++++++++++++ validation/optim/muldiv-minus-one.c | 13 +++++++++++++ 2 files changed, 25 insertions(+) create mode 100644 validation/optim/muldiv-minus-one.c