1 files changed, 88 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/s390x/ggen.go b/src/cmd/compile/internal/s390x/ggen.go
new file mode 100644
index 0000000..5a837d8
--- /dev/null
+++ b/src/cmd/compile/internal/s390x/ggen.go
@@ -0,0 +1,88 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package s390x
+
+import (
+	"cmd/compile/internal/gc"
+	"cmd/internal/obj"
+	"cmd/internal/obj/s390x"
+)
+
+// clearLoopCutOff is the (somewhat arbitrary) value above which it is better
+// to have a loop of clear instructions (e.g. XCs) rather than just generating
+// multiple instructions (i.e. loop unrolling).
+// Must be between 256 and 4096.
+const clearLoopCutoff = 1024
+
+// zerorange clears the stack in the given range.
+func zerorange(pp *gc.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog {
+	if cnt == 0 {
+		return p
+	}
+
+	// Adjust the frame to account for LR.
+	off += gc.Ctxt.FixedFrameSize()
+	reg := int16(s390x.REGSP)
+
+	// If the off cannot fit in a 12-bit unsigned displacement then we
+	// need to create a copy of the stack pointer that we can adjust.
+	// We also need to do this if we are going to loop.
+	if off < 0 || off > 4096-clearLoopCutoff || cnt > clearLoopCutoff {
+		p = pp.Appendpp(p, s390x.AADD, obj.TYPE_CONST, 0, off, obj.TYPE_REG, s390x.REGRT1, 0)
+		p.Reg = int16(s390x.REGSP)
+		reg = s390x.REGRT1
+		off = 0
+	}
+
+	// Generate a loop of large clears.
+	if cnt > clearLoopCutoff {
+		ireg := int16(s390x.REGRT2) // register holds number of remaining loop iterations
+		p = pp.Appendpp(p, s390x.AMOVD, obj.TYPE_CONST, 0, cnt/256, obj.TYPE_REG, ireg, 0)
+		p = pp.Appendpp(p, s390x.ACLEAR, obj.TYPE_CONST, 0, 256, obj.TYPE_MEM, reg, off)
+		pl := p
+		p = pp.Appendpp(p, s390x.AADD, obj.TYPE_CONST, 0, 256, obj.TYPE_REG, reg, 0)
+		p = pp.Appendpp(p, s390x.ABRCTG, obj.TYPE_REG, ireg, 0, obj.TYPE_BRANCH, 0, 0)
+		gc.Patch(p, pl)
+		cnt = cnt % 256
+	}
+
+	// Generate remaining clear instructions without a loop.
+	for cnt > 0 {
+		n := cnt
+
+		// Can clear at most 256 bytes per instruction.
+		if n > 256 {
+			n = 256
+		}
+
+		switch n {
+		// Handle very small clears with move instructions.
+		case 8, 4, 2, 1:
+			ins := s390x.AMOVB
+			switch n {
+			case 8:
+				ins = s390x.AMOVD
+			case 4:
+				ins = s390x.AMOVW
+			case 2:
+				ins = s390x.AMOVH
+			}
+			p = pp.Appendpp(p, ins, obj.TYPE_CONST, 0, 0, obj.TYPE_MEM, reg, off)
+
+		// Handle clears that would require multiple move instructions with CLEAR (assembled as XC).
+		default:
+			p = pp.Appendpp(p, s390x.ACLEAR, obj.TYPE_CONST, 0, n, obj.TYPE_MEM, reg, off)
+		}
+
+		cnt -= n
+		off += n
+	}
+
+	return p
+}
+
+func ginsnop(pp *gc.Progs) *obj.Prog {
+	return pp.Prog(s390x.ANOPH)
+}