[PATCH 17/22] sub: simplify (x + y) - x --> y

[Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>]

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 simplify.c                                | 8 ++++++++
 validation/optim/simplify-same-add-subl.c | 1 -
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/simplify.c b/simplify.c
index 187d4fc0c9ab..cb401d8fac9f 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1382,9 +1382,17 @@ static int simplify_add(struct instruction *insn)
 
 static int simplify_sub(struct instruction *insn)
 {
+	pseudo_t src1 = insn->src1;
 	pseudo_t src2 = insn->src2;
 	struct instruction *def;
 
+	switch (DEF_OPCODE(def, src1)) {
+	case OP_ADD:
+		if (def->src1 == src2)		// (x + y) - x --> y
+			return replace_with_pseudo(insn, def->src2);
+		break;
+	}
+
 	switch (DEF_OPCODE(def, src2)) {
 	case OP_NEG:				// (x - -y) --> (x + y)
 		insn->opcode = OP_ADD;
diff --git a/validation/optim/simplify-same-add-subl.c b/validation/optim/simplify-same-add-subl.c
index 1f17ef0b968e..394e7dc5a404 100644
--- a/validation/optim/simplify-same-add-subl.c
+++ b/validation/optim/simplify-same-add-subl.c
@@ -3,7 +3,6 @@ int add_subl(int x, int y) { return (x + y) - x; }
 /*
  * check-name: simplify-same-add-subl
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-start
 add_subl:
-- 
2.28.0