[dev.ssa] cmd/compile: fix spill sizes
In code that does:
var x, z int32
var y int64
z = phi(x, int32(y))
We silently drop the int32 cast because truncation is a no-op.
The phi operation needs to make sure it uses the size of the
phi, not the size of its arguments, when generating spills.
Change-Id: I1f7baf44f019256977a46fdd3dad1972be209042
Reviewed-on: https://go-review.googlesource.com/18390
Reviewed-by: David Chase <drchase@google.com>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 55ab8ce2..eee3051 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -4536,6 +4536,9 @@
// where v should be spilled.
func autoVar(v *ssa.Value) (*Node, int64) {
loc := v.Block.Func.RegAlloc[v.ID].(ssa.LocalSlot)
+ if v.Type.Size() > loc.Type.Size() {
+ v.Fatalf("spill/restore type %s doesn't fit in slot type %s", v.Type, loc.Type)
+ }
return loc.N.(*Node), loc.Off
}
diff --git a/src/cmd/compile/internal/gc/ssa_test.go b/src/cmd/compile/internal/gc/ssa_test.go
index 74fa847..d0c44b5 100644
--- a/src/cmd/compile/internal/gc/ssa_test.go
+++ b/src/cmd/compile/internal/gc/ssa_test.go
@@ -95,3 +95,5 @@
func TestCopy(t *testing.T) { runTest(t, "copy_ssa.go") }
func TestUnsafe(t *testing.T) { runTest(t, "unsafe_ssa.go") }
+
+func TestPhi(t *testing.T) { runTest(t, "phi_ssa.go") }
diff --git a/src/cmd/compile/internal/gc/testdata/phi_ssa.go b/src/cmd/compile/internal/gc/testdata/phi_ssa.go
new file mode 100644
index 0000000..e855070
--- /dev/null
+++ b/src/cmd/compile/internal/gc/testdata/phi_ssa.go
@@ -0,0 +1,103 @@
+// 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 main
+
+// Test to make sure spills of cast-shortened values
+// don't end up spilling the pre-shortened size instead
+// of the post-shortened size.
+
+import (
+ "fmt"
+ "runtime"
+)
+
+// unfoldable true
+var true_ = true
+
+var data1 [26]int32
+var data2 [26]int64
+
+func init() {
+ for i := 0; i < 26; i++ {
+ // If we spill all 8 bytes of this datum, the 1 in the high-order 4 bytes
+ // will overwrite some other variable in the stack frame.
+ data2[i] = 0x100000000
+ }
+}
+
+func foo() int32 {
+ var a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z int32
+ if true_ {
+ a = data1[0]
+ b = data1[1]
+ c = data1[2]
+ d = data1[3]
+ e = data1[4]
+ f = data1[5]
+ g = data1[6]
+ h = data1[7]
+ i = data1[8]
+ j = data1[9]
+ k = data1[10]
+ l = data1[11]
+ m = data1[12]
+ n = data1[13]
+ o = data1[14]
+ p = data1[15]
+ q = data1[16]
+ r = data1[17]
+ s = data1[18]
+ t = data1[19]
+ u = data1[20]
+ v = data1[21]
+ w = data1[22]
+ x = data1[23]
+ y = data1[24]
+ z = data1[25]
+ } else {
+ a = int32(data2[0])
+ b = int32(data2[1])
+ c = int32(data2[2])
+ d = int32(data2[3])
+ e = int32(data2[4])
+ f = int32(data2[5])
+ g = int32(data2[6])
+ h = int32(data2[7])
+ i = int32(data2[8])
+ j = int32(data2[9])
+ k = int32(data2[10])
+ l = int32(data2[11])
+ m = int32(data2[12])
+ n = int32(data2[13])
+ o = int32(data2[14])
+ p = int32(data2[15])
+ q = int32(data2[16])
+ r = int32(data2[17])
+ s = int32(data2[18])
+ t = int32(data2[19])
+ u = int32(data2[20])
+ v = int32(data2[21])
+ w = int32(data2[22])
+ x = int32(data2[23])
+ y = int32(data2[24])
+ z = int32(data2[25])
+ }
+ // Lots of phis of the form phi(int32,int64) of type int32 happen here.
+ // Some will be stack phis. For those stack phis, make sure the spill
+ // of the second argument uses the phi's width (4 bytes), not its width
+ // (8 bytes). Otherwise, a random stack slot gets clobbered.
+
+ runtime.Gosched()
+ return a + b + c + d + e + f + g + h + i + j + k + l + m + n + o + p + q + r + s + t + u + v + w + x + y + z
+}
+
+func main() {
+ want := int32(0)
+ got := foo()
+ if got != want {
+ fmt.Printf("want %d, got %d\n", want, got)
+ panic("bad")
+ }
+}
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index d7c4674..27deeba 100644
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -1223,7 +1223,10 @@
r := e.findRegFor(v.Type)
x = v.copyInto(e.p)
e.set(r, vid, x, false)
- x = e.p.NewValue1(x.Line, OpStoreReg, x.Type, x)
+ // Make sure we spill with the size of the slot, not the
+ // size of x (which might be wider due to our dropping
+ // of narrowing conversions).
+ x = e.p.NewValue1(x.Line, OpStoreReg, loc.(LocalSlot).Type, x)
}
} else {
// Emit move from src to dst.
@@ -1232,7 +1235,7 @@
if dstReg {
x = e.p.NewValue1(c.Line, OpCopy, c.Type, c)
} else {
- x = e.p.NewValue1(c.Line, OpStoreReg, c.Type, c)
+ x = e.p.NewValue1(c.Line, OpStoreReg, loc.(LocalSlot).Type, c)
}
} else {
if dstReg {
@@ -1255,7 +1258,7 @@
r := e.findRegFor(c.Type)
t := e.p.NewValue1(c.Line, OpLoadReg, c.Type, c)
e.set(r, vid, t, false)
- x = e.p.NewValue1(c.Line, OpStoreReg, c.Type, t)
+ x = e.p.NewValue1(c.Line, OpStoreReg, loc.(LocalSlot).Type, t)
}
}
}
