cmd/compile: allow OpArgXXXReg comes before LoweredGetClosurePtr

Both OpArgXXXReg and LoweredGetClosurePtr must come very early,
because they carry registers that are technically live on entry.
But no need to impose ordering requirement between them.

Change-Id: Iee1db6239a75e5b381e0ad25ba5503169333217b
Reviewed-on: https://go-review.googlesource.com/c/go/+/309629
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index de60cbf390eaf217987c1388ef3548b75a8889cc..60a849db23ea3f2c1f0942ee97259e34bd8c1ac8 100644 (file)
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -7097,15 +7097,26 @@ func CheckLoweredPhi(v *ssa.Value) {
        }
 }
 
-// CheckLoweredGetClosurePtr checks that v is the first instruction in the function's entry block.
+// CheckLoweredGetClosurePtr checks that v is the first instruction in the function's entry block,
+// except for incoming in-register arguments.
 // The output of LoweredGetClosurePtr is generally hardwired to the correct register.
 // That register contains the closure pointer on closure entry.
 func CheckLoweredGetClosurePtr(v *ssa.Value) {
        entry := v.Block.Func.Entry
-       // TODO register args: not all the register-producing ops can come first.
-       if entry != v.Block || entry.Values[0] != v {
+       if entry != v.Block {
                base.Fatalf("in %s, badly placed LoweredGetClosurePtr: %v %v", v.Block.Func.Name, v.Block, v)
        }
+       for _, w := range entry.Values {
+               if w == v {
+                       break
+               }
+               switch w.Op {
+               case ssa.OpArgIntReg, ssa.OpArgFloatReg:
+                       // okay
+               default:
+                       base.Fatalf("in %s, badly placed LoweredGetClosurePtr: %v %v", v.Block.Func.Name, v.Block, v)
+               }
+       }
 }
 
 // CheckArgReg ensures that v is in the function's entry block.