[09/10] cmps: canonicalize SEL(x {<,<=} y, a, b) --> SEL(x {>=,>} y, b, a)

Commit Message

Luc Van Oostenryck Jan. 26, 2021, 10:04 p.m. UTC

Both compares and OP_SELECT are anti-symmetrical: swapping
the arguments is equivalent to inversing the condition.
As consequence, when combined, they're symmetrical:
swapping the arguments of the compare (or equivalently reversing
the direction of the compare) and swapping the operand of the
OP_SELECT is a no-op, both forms are equivalent.

So, canonicalize these to always use OP_GT or OP_GE.

Signed-off-by: Luc Van Oostenryck <[e-mail]>
---
 simplify.c                            | 7 +++++++
 validation/optim/canonical-cmps-sel.c | 1 -
 2 files changed, 7 insertions(+), 1 deletion(-)

Patch

diff --git a/simplify.c b/simplify.c
index b29f5d5b2444..10cdf50dcbf1 100644
--- a/simplify.c
+++ b/simplify.c
@@ -2301,6 +2301,13 @@  static int simplify_select(struct instruction *insn)
 		if (src2 == def->src1 && src1 == def->src2)
 			return replace_with_pseudo(insn, src1); // SEL(y!=x,x,y) --> x
 		break;
+	case OP_SET_LE: case OP_SET_LT:
+	case OP_SET_BE: case OP_SET_B:
+		if (!one_use(cond))
+			break;
+		// SEL(x {<,<=} y, a, b) --> SEL(x {>=,>} y, b, a)
+		def->opcode = opcode_negate(def->opcode);
+		return switch_pseudo(insn, &insn->src2, insn, &insn->src3);
 	case OP_SEL:
 		if (constant(def->src2) && constant(def->src3)) {
 			// Is the def of the conditional another select?
diff --git a/validation/optim/canonical-cmps-sel.c b/validation/optim/canonical-cmps-sel.c
index f0a0effc7954..bba5e5c894f8 100644
--- a/validation/optim/canonical-cmps-sel.c
+++ b/validation/optim/canonical-cmps-sel.c
@@ -19,7 +19,6 @@  _Bool sel_leu(unsigned int a, unsigned int b, int x, int y)
 /*
  * check-name: canonical-cmps-sel
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-returns: 1