cmp: simplify compares and sign/zero extend

Compare instructions with both operands sign or zero-extended
from the same original size are equivalent to a compare of
the original values. If the values were zero-extended, a signed
compare becomes an unsigned one.

Simplify away the sign/zero-extensions.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

3 files changed, 42 insertions, 12 deletions

diff --git a/simplify.c b/simplify.c
index 7538c939..d56d4c89 100644
--- a/simplify.c
+++ b/simplify.c
@@ -423,6 +423,22 @@ static inline bool is_signed_constant(long long val, unsigned osize, unsigned ns
 }
 
 ///
+// is @src generated by an instruction with the given opcode and size?
+static inline pseudo_t is_same_op(pseudo_t src, int op, unsigned osize)
+{
+	struct instruction *def;
+
+	if (src->type != PSEUDO_REG)
+		return NULL;
+	def = src->def;
+	if (def->opcode != op)
+		return NULL;
+	if (def->orig_type->bit_size != osize)
+		return NULL;
+	return def->src;
+}
+
+///
 // replace the operand of an instruction
 // @insn: the instruction
 // @pp: the address of the instruction's operand
@@ -1570,6 +1586,30 @@ static int simplify_sub(struct instruction *insn)
 	return 0;
 }
 
+static int simplify_compare(struct instruction *insn)
+{
+	pseudo_t src1 = insn->src1;
+	pseudo_t src2 = insn->src2;
+	struct instruction *def;
+	unsigned int osize;
+	pseudo_t src;
+
+	switch (DEF_OPCODE(def, src1)) {
+	case OP_SEXT: case OP_ZEXT:
+		osize = def->orig_type->bit_size;
+		if ((src = is_same_op(src2, def->opcode, osize))) {
+			const struct opcode_table *op = &opcode_table[insn->opcode];
+			if ((def->opcode == OP_ZEXT) && (op->flags & OPF_SIGNED))
+				insn->opcode = op->sign;
+			insn->itype = def->orig_type;
+			replace_pseudo(insn, &insn->src1, def->src);
+			return replace_pseudo(insn, &insn->src2, src);
+		}
+		break;
+	}
+	return 0;
+}
+
 static int simplify_constant_unop(struct instruction *insn)
 {
 	long long val = insn->src1->value;
@@ -2083,17 +2123,9 @@ int simplify_instruction(struct instruction *insn)
 	case OP_DIVS:
 	case OP_MODU:
 	case OP_MODS:
-	case OP_SET_EQ:
-	case OP_SET_NE:
-	case OP_SET_LE:
-	case OP_SET_GE:
-	case OP_SET_LT:
-	case OP_SET_GT:
-	case OP_SET_B:
-	case OP_SET_A:
-	case OP_SET_BE:
-	case OP_SET_AE:
 		break;
+	case OP_BINCMP ... OP_BINCMP_END:
+		return simplify_compare(insn);
 	case OP_LOAD:
 	case OP_STORE:
 		return simplify_memop(insn);
diff --git a/validation/optim/cmp-sext-sext.c b/validation/optim/cmp-sext-sext.c
index ba6ed54e..3bd22fb7 100644
--- a/validation/optim/cmp-sext-sext.c
+++ b/validation/optim/cmp-sext-sext.c
@@ -11,7 +11,6 @@ _Bool cmpu_sext_sext(ARGS(INT32)) { return TEST(UINT64, UINT32, a, < , b); }
 /*
  * check-name: cmp-sext-sext
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1
diff --git a/validation/optim/cmp-zext-zext.c b/validation/optim/cmp-zext-zext.c
index 9f188297..88f9078f 100644
--- a/validation/optim/cmp-zext-zext.c
+++ b/validation/optim/cmp-zext-zext.c
@@ -11,7 +11,6 @@ _Bool cmpu_zext_zext(ARGS(UINT32)) { return TEST(UINT64, UINT32, a, < , b); }
 /*
  * check-name: cmp-zext-zext
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1