cmd/compile/internal/ssa: lower builtins much later

* Move lowering into a separate pass.
* SliceLen/SliceCap is now available to various intermediate passes
which use useful for bounds checking.
* Add a second opt pass to handle the new opportunities

Decreases the code size of binaries in pkg/tool/linux_amd64
by ~45K.

Updates #14564 #14606

Change-Id: I5b2bd6202181c50623a3585fbf15c0d6db6d4685
Reviewed-on: https://go-review.googlesource.com/20172
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ssa/rewritedec.go b/src/cmd/compile/internal/ssa/rewritedec.go
new file mode 100644
index 0000000000..e62c789368
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/rewritedec.go
@@ -0,0 +1,118 @@
+// autogenerated from gen/dec.rules: do not edit!
+// generated with: cd gen; go run *.go
+
+package ssa
+
+import "math"
+
+var _ = math.MinInt8 // in case not otherwise used
+func rewriteValuedec(v *Value, config *Config) bool {
+	switch v.Op {
+	case OpSliceCap:
+		return rewriteValuedec_OpSliceCap(v, config)
+	case OpSliceLen:
+		return rewriteValuedec_OpSliceLen(v, config)
+	case OpSlicePtr:
+		return rewriteValuedec_OpSlicePtr(v, config)
+	case OpStringLen:
+		return rewriteValuedec_OpStringLen(v, config)
+	case OpStringPtr:
+		return rewriteValuedec_OpStringPtr(v, config)
+	}
+	return false
+}
+func rewriteValuedec_OpSliceCap(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SliceCap (SliceMake _ _ cap))
+	// cond:
+	// result: cap
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		cap := v.Args[0].Args[2]
+		v.reset(OpCopy)
+		v.Type = cap.Type
+		v.AddArg(cap)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpSliceLen(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SliceLen (SliceMake _ len _))
+	// cond:
+	// result: len
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		len := v.Args[0].Args[1]
+		v.reset(OpCopy)
+		v.Type = len.Type
+		v.AddArg(len)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpSlicePtr(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SlicePtr (SliceMake ptr _ _ ))
+	// cond:
+	// result: ptr
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		ptr := v.Args[0].Args[0]
+		v.reset(OpCopy)
+		v.Type = ptr.Type
+		v.AddArg(ptr)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpStringLen(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (StringLen (StringMake _ len))
+	// cond:
+	// result: len
+	for {
+		if v.Args[0].Op != OpStringMake {
+			break
+		}
+		len := v.Args[0].Args[1]
+		v.reset(OpCopy)
+		v.Type = len.Type
+		v.AddArg(len)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpStringPtr(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (StringPtr (StringMake ptr _))
+	// cond:
+	// result: ptr
+	for {
+		if v.Args[0].Op != OpStringMake {
+			break
+		}
+		ptr := v.Args[0].Args[0]
+		v.reset(OpCopy)
+		v.Type = ptr.Type
+		v.AddArg(ptr)
+		return true
+	}
+	return false
+}
+func rewriteBlockdec(b *Block) bool {
+	switch b.Kind {
+	}
+	return false
+}