[PATCH 13/22] sub: simplify (C - y) + D --> eval(C+D) - y

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

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 simplify.c                               | 20 ++++++++++++++++++++
 validation/optim/simplify-cte-sub-addl.c |  1 -
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/simplify.c b/simplify.c
index 7d1897e65b07..929a177631e5 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1096,6 +1096,24 @@ static int simplify_constant_mask(struct instruction *insn, unsigned long long m
 	return 0;
 }
 
+static int simplify_const_rightadd(struct instruction *def, struct instruction *insn)
+{
+	unsigned size = insn->size;
+	pseudo_t src2 = insn->src2;
+
+	switch (def->opcode) {
+	case OP_SUB:
+		if (constant(def->src1)) { // (C - y) + D --> eval(C+D) - y
+			pseudo_t val = eval_op(OP_ADD, size, def->src1, src2);
+			insn->opcode = OP_SUB;
+			use_pseudo(insn, def->src2, &insn->src2);
+			return replace_pseudo(insn, &insn->src1, val);
+		}
+		break;
+	}
+	return 0;
+}
+
 static int simplify_constant_rightside(struct instruction *insn)
 {
 	long long value = insn->src2->value;
@@ -1128,6 +1146,8 @@ static int simplify_constant_rightside(struct instruction *insn)
 	case OP_ADD:
 		if (!value)
 			return replace_with_pseudo(insn, insn->src1);
+		if (insn->src1->type == PSEUDO_REG)	// (x # y) + z
+			changed |= simplify_const_rightadd(insn->src1->def, insn);
 		return changed;
 	case OP_ASR:
 	case OP_SHL:
diff --git a/validation/optim/simplify-cte-sub-addl.c b/validation/optim/simplify-cte-sub-addl.c
index 49e510062c03..137029636f2d 100644
--- a/validation/optim/simplify-cte-sub-addl.c
+++ b/validation/optim/simplify-cte-sub-addl.c
@@ -3,7 +3,6 @@ int cte_sub_addl(int x) { return (1 - x) + 1; }
 /*
  * check-name: simplify-cte-sub-addl
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-contains: sub\\..*\\$2, %arg1
-- 
2.28.0