[dev.ssa] cmd/compile: be safer about uintptr/unsafe.Pointer conversions
Make sure that when a pointer value is live across a function
call, we save it as a pointer. (And similarly a uintptr
live across a function call should not be saved as a pointer.)
Add a nasty test case.
This is probably what is preventing the merge from master
to dev.ssa. Signs point to something like this bug happening
in mallocgc.
Change-Id: Ib23fa1251b8d1c50d82c6a448cb4a4fc28219029
Reviewed-on: https://go-review.googlesource.com/16830
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index ead0cfd..e57dd93 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -236,9 +236,14 @@
{name: "Sqrt"}, // sqrt(arg0), float64 only
// Data movement
- {name: "Phi"}, // select an argument based on which predecessor block we came from
- {name: "Copy"}, // output = arg0
- {name: "Convert"}, // output = arg0 -- a copy that converts to/from a pointer
+ {name: "Phi"}, // select an argument based on which predecessor block we came from
+ {name: "Copy"}, // output = arg0
+ // Convert converts between pointers and integers.
+ // We have a special op for this so as to not confuse GC
+ // (particularly stack maps). It takes a memory arg so it
+ // gets correctly ordered with respect to GC safepoints.
+ // arg0=ptr/int arg1=mem, output=int/ptr
+ {name: "Convert"},
// constants. Constant values are stored in the aux field.
// booleans have a bool aux field, strings have a string aux
