cmd/compile: don't inline functions that call runtime.getcaller{pc,sp}

runtime.getcaller{pc,sp} expect their argument to be a pointer to the
caller's first function argument. This assumption breaks when the caller
is inlined. For example, with -l=4, calls to runtime.entersyscall (which
calls getcallerpc) are inlined and that breaks multiple cgo tests.

This change modifies the compiler to refuse to inline functions that
call runtime.getcaller{pc,sp}. Alternatively, we could mark these
functions //go:noinline but that limits optimization opportunities if
the calls to getcaller{pc,sp} are eliminated as dead code.

Previously TestCgoPprofPIE, TestCgoPprof, and TestCgoCallbackGC failed
with -l=4. Now all of the runtime tests pass with -l=4.

Change-Id: I258bca9025e20fc451e673a18f862b5da1e07ae7
Reviewed-on: https://go-review.googlesource.com/40998
Run-TryBot: David Lazar <lazard@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/cmd/compile/internal/gc/inl.go b/src/cmd/compile/internal/gc/inl.go
index c9d1a0c0352eae9f9c947a480130a19c84798c0f..464b6e0e65ada0aa63186466b3993ed5b293acfa 100644 (file)
--- a/src/cmd/compile/internal/gc/inl.go
+++ b/src/cmd/compile/internal/gc/inl.go
@@ -206,6 +206,16 @@ func ishairy(n *Node, budget *int32, reason *string) bool {
                        *budget--
                        break
                }
+               // Functions that call runtime.getcaller{pc,sp} can not be inlined
+               // because getcaller{pc,sp} expect a pointer to the caller's first argument.
+               if n.Left.Op == ONAME && n.Left.Class == PFUNC && isRuntimePkg(n.Left.Sym.Pkg) {
+                       fn := n.Left.Sym.Name
+                       if fn == "getcallerpc" || fn == "getcallersp" {
+                               *reason = "call to " + fn
+                               return true
+                       }
+               }
+
                if fn := n.Left.Func; fn != nil && fn.Inl.Len() != 0 {
                        *budget -= fn.InlCost
                        break