Most binops can be simplified when their two operands are
identical. For example '(x ^ x)' can be simplified into '0'.
The cases '(x / x)' and '(x % x)' are not simplified since this
is correct only when x is not zero.
The cases '(x || x)' and '(x && x)' are not simplified because
it's only correct when the operands are booleans/have already
been compared against zero and the linearization don't enforce that.
This patch add the code for these simplifications as well as
their corresponding test cases.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 35 ++++++++++++++++++++++++++
validation/optim/binops-same-args.c | 49 +++++++++++++++++++++++++++++++++++++
2 files changed, 84 insertions(+)
create mode 100644 validation/optim/binops-same-args.c
diff --git a/simplify.c b/simplify.c
index b5cd0ea7..fde72f0a 100644
--- a/simplify.c
+++ b/simplify.c
@@ -488,6 +488,39 @@ static int simplify_constant_binop(struct instruction *insn)
return REPEAT_CSE;
}
+static int simplify_binop_same_args(struct instruction *insn, pseudo_t arg)
+{
+ switch (insn->opcode) {
+ case OP_SET_NE:
+ case OP_SET_LT: case OP_SET_GT:
+ case OP_SET_B: case OP_SET_A:
+ case OP_SUB:
+ case OP_XOR:
+ return replace_with_pseudo(insn, value_pseudo(0));
+
+ case OP_SET_EQ:
+ case OP_SET_LE: case OP_SET_GE:
+ case OP_SET_BE: case OP_SET_AE:
+ return replace_with_pseudo(insn, value_pseudo(1));
+
+ case OP_AND:
+ case OP_OR:
+ return replace_with_pseudo(insn, arg);
+
+ case OP_AND_BOOL:
+ case OP_OR_BOOL:
+ // simplification is correct only if the operands
+ // have already been compared against zero which
+ // is not enforced.
+ break;
+
+ default:
+ break;
+ }
+
+ return 0;
+}
+
static int simplify_binop(struct instruction *insn)
{
if (dead_insn(insn, &insn->src1, &insn->src2, NULL))
@@ -499,6 +532,8 @@ static int simplify_binop(struct instruction *insn)
}
if (constant(insn->src2))
return simplify_constant_rightside(insn);
+ if (insn->src1 == insn->src2)
+ return simplify_binop_same_args(insn, insn->src1);
return 0;
}
diff --git a/validation/optim/binops-same-args.c b/validation/optim/binops-same-args.c
new file mode 100644
index 00000000..9285655d
--- /dev/null
+++ b/validation/optim/binops-same-args.c
@@ -0,0 +1,49 @@
+typedef unsigned int u32;
+
+int ssub(int a) { return a - a; }
+u32 usub(u32 a) { return a - a; }
+
+int sdiv(int a) { return a / a; }
+u32 udiv(u32 a) { return a / a; }
+int smod(int a) { return a % a; }
+u32 umod(u32 a) { return a % a; }
+
+int seq(int a) { return a == a; }
+int sne(int a) { return a != a; }
+int slt(int a) { return a < a; }
+int sgt(int a) { return a > a; }
+int sle(int a) { return a <= a; }
+int sge(int a) { return a >= a; }
+
+u32 ueq(u32 a) { return a == a; }
+u32 une(u32 a) { return a != a; }
+u32 ult(u32 a) { return a < a; }
+u32 ugt(u32 a) { return a > a; }
+u32 ule(u32 a) { return a <= a; }
+u32 uge(u32 a) { return a >= a; }
+
+u32 xor(u32 a) { return a ^ a; }
+
+u32 ior(u32 a) { return a | a; }
+u32 and(u32 a) { return a & a; }
+
+/*
+ * check-name: double-unop
+ * check-command: test-linearize -Wno-decl $file
+ * check-output-ignore
+ *
+ * check-output-excludes: sub\\.
+ * check-output-contains: divs\\.
+ * check-output-contains: divu\\.
+ * check-output-contains: mods\\.
+ * check-output-contains: modu\\.
+ * check-output-excludes: seteq\\.
+ * check-output-excludes: setne\\.
+ * check-output-excludes: set[gl]t\\.
+ * check-output-excludes: set[gl]e\\.
+ * check-output-excludes: set[ab]\\.
+ * check-output-excludes: set[ab]e\\.
+ * check-output-excludes: xor\\.
+ * check-output-excludes: or\\.
+ * check-output-excludes: and\\.
+ */
--
2.10.2
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