If-conversion RFC 4 - x86 only (for now), use cmovXX

Replacement of tiny conditional jump graphlets with
conditional move instructions.

Currently enabled only for x86. Arm64 support using cselXX
will be essentially identical.

Adds (internal) frontend sel0/sel1 ops with flag-specific
backend xselXX following jnz implementation pattern.

Testing: standard QBE, cproc, harec, hare, roland

1 files changed, 12 insertions, 1 deletions

diff --git a/util.c b/util.c
index 3b5c09d..c891c4e 100644
--- a/util.c
+++ b/util.c
@@ -164,7 +164,7 @@ addins(Ins **pvins, uint *pnins, Ins *i)
 }
 
 void
-addbins(Blk *b, Ins **pvins, uint *pnins)
+addbins(Ins **pvins, uint *pnins, Blk *b)
 {
 	Ins *i;
 
@@ -281,6 +281,17 @@ igroup(Blk *b, Ins *i, Ins **i0, Ins **i1)
 		assert(i < ie);
 		*i1 = i + 1;
 		return;
+	case Osel1:
+		for (; i>ib && (i-1)->op == Osel1; i--)
+			;
+		assert(i->op == Osel0);
+		/* fall through */
+	case Osel0:
+		*i0 = i++;
+		for (; i<ie && i->op == Osel1; i++)
+			;
+		*i1 = i;
+		return;
 	default:
 		if (ispar(i->op))
 			goto case_Opar;