[3/3] simplify casts bool -> int -> bool

Commit Message

Luc Van Oostenryck April 12, 2017, 2:18 p.m. UTC

Because of C's integer promotion, in code like 'a == 0',
the operand 'a' must be promoted to int, which result in
following linearization if the type of 'a' was _Bool:
	cast.32  %t <- (1) %a
	setne.32 %r <- %t, $0
While required by the standard, this promotion is unneeded
in the given situation.

Change this by simplifying away such casts.

Signed-off-by: Luc Van Oostenryck <[e-mail]>
---
 simplify.c                       | 18 +++++++++++++++++-
 validation/optim/bool-int-bool.c | 12 ++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 validation/optim/bool-int-bool.c

Patch

diff --git a/simplify.c b/simplify.c
index 775c1e2dd..96448a666 100644
--- a/simplify.c
+++ b/simplify.c
@@ -445,9 +445,25 @@  static int simplify_seteq_setne(struct instruction *insn, long long value)
 		remove_usage(old, &insn->src1);
 		return REPEAT_CSE;
 
+	case OP_CAST:
+		if (def->orig_type->bit_size != 1)
+			break;
+
+		// Convert:
+		//	cast.n	%t <- (1) %a
+		//	setne.m %r <- %t, $0
+		// into:
+		//	...
+		//	setne.m %r <- %a, $0
+		// and similar for setne/eq ... 0/1
+		use_pseudo(insn, def->src1, &insn->src1);
+		remove_usage(old, &insn->src1);
+		return REPEAT_CSE;
+
 	default:
-		return 0;
+		break;
 	}
+	return 0;
 }
 
 static int simplify_constant_rightside(struct instruction *insn)
diff --git a/validation/optim/bool-int-bool.c b/validation/optim/bool-int-bool.c
new file mode 100644
index 000000000..de34a68bb
--- /dev/null
+++ b/validation/optim/bool-int-bool.c
@@ -0,0 +1,12 @@ 
+_Bool beq0(_Bool a) { return (a == 0); }
+_Bool beq1(_Bool a) { return (a == 1); }
+_Bool bne0(_Bool a) { return (a != 0); }
+_Bool bne1(_Bool a) { return (a != 1); }
+
+/*
+ * check-name: bool - int - bool constants
+ * check-command: test-linearize -Wno-decl $file
+ *
+ * check-output-ignore
+ * check-output-excludes: cast\\.
+ */