3 files changed, 24 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules
index 58872ca85a..b16aa473cd 100644
--- a/src/cmd/compile/internal/ssa/_gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/_gen/generic.rules
@@ -2079,6 +2079,9 @@
 	&& warnRule(fe.Debug_checknil(), v, "removed nil check")
 	=> ptr
 
+// .dict args are always non-nil.
+(NilCheck ptr:(Arg {sym}) _) && isDictArgSym(sym) => ptr
+
 // Nil checks of nil checks are redundant.
 // See comment at the end of https://go-review.googlesource.com/c/go/+/537775.
 (NilCheck ptr:(NilCheck _ _) _ ) => ptr
diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index 6d83ba5653..880c2223ef 100644
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -6,9 +6,11 @@ package ssa
 
 import (
 	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/logopt"
 	"cmd/compile/internal/reflectdata"
 	"cmd/compile/internal/rttype"
+	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/s390x"
@@ -2744,3 +2746,7 @@ func panicBoundsCToAux(p PanicBoundsC) Aux {
 func panicBoundsCCToAux(p PanicBoundsCC) Aux {
 	return p
 }
+
+func isDictArgSym(sym Sym) bool {
+	return sym.(*ir.Name).Sym().Name == typecheck.LocalDictName
+}
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index 7e23194e6a..5e0135be3a 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -21393,6 +21393,21 @@ func rewriteValuegeneric_OpNilCheck(v *Value) bool {
 		v.copyOf(ptr)
 		return true
 	}
+	// match: (NilCheck ptr:(Arg {sym}) _)
+	// cond: isDictArgSym(sym)
+	// result: ptr
+	for {
+		ptr := v_0
+		if ptr.Op != OpArg {
+			break
+		}
+		sym := auxToSym(ptr.Aux)
+		if !(isDictArgSym(sym)) {
+			break
+		}
+		v.copyOf(ptr)
+		return true
+	}
 	// match: (NilCheck ptr:(NilCheck _ _) _ )
 	// result: ptr
 	for {