diff --git a/resources/sksl/metal/OutParams.sksl b/resources/sksl/metal/OutParams.sksl
index a7451e6..c507d8c 100644
--- a/resources/sksl/metal/OutParams.sksl
+++ b/resources/sksl/metal/OutParams.sksl
@@ -28,6 +28,8 @@
 void out_bool3(out bool3 v) { v = bool3(true);  }
 void out_bool4(out bool4 v) { v = bool4(false); }
 
+void out_pair(out half v1, out half v2) { v1 = 1; v2 = 2; }
+
 void main() {
     half     h;    out_half (h);
     half2    h2;   out_half2(h2);
@@ -38,6 +40,13 @@
                    out_half4(h4.zwxy);
     sk_FragColor = half4(h, h2.x, h3.x, h4.x);
 
+    half     h1;
+    out_pair(h, h1);
+    out_pair(h, h);
+    out_pair(h2.x, h2.y);
+    out_pair(h2.x, h2.x);
+    out_pair(h2.x, h3.x);
+
     half2x2  h2x2; out_half2x2(h2x2);
     half3x3  h3x3; out_half3x3(h3x3);
     half4x4  h4x4; out_half4x4(h4x4);
diff --git a/src/sksl/SkSLMetalCodeGenerator.cpp b/src/sksl/SkSLMetalCodeGenerator.cpp
index 8b58453..88666b3 100644
--- a/src/sksl/SkSLMetalCodeGenerator.cpp
+++ b/src/sksl/SkSLMetalCodeGenerator.cpp
@@ -232,6 +232,11 @@
     SkASSERT(outVars.size() == arguments.size());
     SkASSERT(outVars.size() == function.parameters().size());
 
+    // We need to detect cases where the caller passes the same variable as an out-param more than
+    // once, and avoid reusing the variable name. (In those cases we can actually just ignore the
+    // redundant input parameter entirely, and not give it any name.)
+    std::unordered_set<const Variable*> writtenVars;
+
     for (int index = 0; index < arguments.count(); ++index) {
         this->write(separator);
         separator = ", ";
@@ -246,10 +251,13 @@
             this->write("&");
         }
         if (outVars[index]) {
-            this->write(" ");
-            fIgnoreVariableReferenceModifiers = true;
-            this->writeVariableReference(*outVars[index]);
-            fIgnoreVariableReferenceModifiers = false;
+            auto [iter, didInsert] = writtenVars.insert(outVars[index]->variable());
+            if (didInsert) {
+                this->write(" ");
+                fIgnoreVariableReferenceModifiers = true;
+                this->writeVariableReference(*outVars[index]);
+                fIgnoreVariableReferenceModifiers = false;
+            }
         } else {
             this->write(" _var");
             this->write(to_string(index));
diff --git a/tests/sksl/metal/OutParams.metal b/tests/sksl/metal/OutParams.metal
index 718cd54..b8f9c31 100644
--- a/tests/sksl/metal/OutParams.metal
+++ b/tests/sksl/metal/OutParams.metal
@@ -48,170 +48,210 @@
     out_half4(_var0);
     h4.zwxy = _var0;
 }
+void out_pair(thread float& v1, thread float& v2);
+void _skOutParamHelper7_out_pair(thread float& h, thread float& h1) {
+    float _var0;
+    float _var1;
+    out_pair(_var0, _var1);
+    h = _var0;
+    h1 = _var1;
+}
+void out_pair(thread float& v1, thread float& v2);
+void _skOutParamHelper8_out_pair(thread float& h, thread float&) {
+    float _var0;
+    float _var1;
+    out_pair(_var0, _var1);
+    h = _var0;
+    h = _var1;
+}
+void out_pair(thread float& v1, thread float& v2);
+void _skOutParamHelper9_out_pair(thread float2& h2, thread float2&) {
+    float _var0;
+    float _var1;
+    out_pair(_var0, _var1);
+    h2.x = _var0;
+    h2.y = _var1;
+}
+void out_pair(thread float& v1, thread float& v2);
+void _skOutParamHelper10_out_pair(thread float2& h2, thread float2&) {
+    float _var0;
+    float _var1;
+    out_pair(_var0, _var1);
+    h2.x = _var0;
+    h2.x = _var1;
+}
+void out_pair(thread float& v1, thread float& v2);
+void _skOutParamHelper11_out_pair(thread float2& h2, thread float3& h3) {
+    float _var0;
+    float _var1;
+    out_pair(_var0, _var1);
+    h2.x = _var0;
+    h3.x = _var1;
+}
 void out_half2x2(thread float2x2& v);
-void _skOutParamHelper7_out_half2x2(thread float2x2& h2x2) {
+void _skOutParamHelper12_out_half2x2(thread float2x2& h2x2) {
     float2x2 _var0;
     out_half2x2(_var0);
     h2x2 = _var0;
 }
 void out_half3x3(thread float3x3& v);
-void _skOutParamHelper8_out_half3x3(thread float3x3& h3x3) {
+void _skOutParamHelper13_out_half3x3(thread float3x3& h3x3) {
     float3x3 _var0;
     out_half3x3(_var0);
     h3x3 = _var0;
 }
 void out_half4x4(thread float4x4& v);
-void _skOutParamHelper9_out_half4x4(thread float4x4& h4x4) {
+void _skOutParamHelper14_out_half4x4(thread float4x4& h4x4) {
     float4x4 _var0;
     out_half4x4(_var0);
     h4x4 = _var0;
 }
 void out_half3(thread float3& v);
-void _skOutParamHelper10_out_half3(thread float3x3& h3x3) {
+void _skOutParamHelper15_out_half3(thread float3x3& h3x3) {
     float3 _var0;
     out_half3(_var0);
     h3x3[1] = _var0;
 }
 void out_half4(thread float4& v);
-void _skOutParamHelper11_out_half4(thread float4x4& h4x4) {
+void _skOutParamHelper16_out_half4(thread float4x4& h4x4) {
     float4 _var0;
     out_half4(_var0);
     h4x4[3].zwxy = _var0;
 }
 void out_half2(thread float2& v);
-void _skOutParamHelper12_out_half2(thread float2x2& h2x2) {
+void _skOutParamHelper17_out_half2(thread float2x2& h2x2) {
     float2 _var0;
     out_half2(_var0);
     h2x2[0] = _var0;
 }
 void out_int(thread int& v);
-void _skOutParamHelper13_out_int(thread int& i) {
+void _skOutParamHelper18_out_int(thread int& i) {
     int _var0;
     out_int(_var0);
     i = _var0;
 }
 void out_int2(thread int2& v);
-void _skOutParamHelper14_out_int2(thread int2& i2) {
+void _skOutParamHelper19_out_int2(thread int2& i2) {
     int2 _var0;
     out_int2(_var0);
     i2 = _var0;
 }
 void out_int3(thread int3& v);
-void _skOutParamHelper15_out_int3(thread int3& i3) {
+void _skOutParamHelper20_out_int3(thread int3& i3) {
     int3 _var0;
     out_int3(_var0);
     i3 = _var0;
 }
 void out_int4(thread int4& v);
-void _skOutParamHelper16_out_int4(thread int4& i4) {
+void _skOutParamHelper21_out_int4(thread int4& i4) {
     int4 _var0;
     out_int4(_var0);
     i4 = _var0;
 }
 void out_int3(thread int3& v);
-void _skOutParamHelper17_out_int3(thread int4& i4) {
+void _skOutParamHelper22_out_int3(thread int4& i4) {
     int3 _var0;
     out_int3(_var0);
     i4.xyz = _var0;
 }
 void out_float(thread float& v);
-void _skOutParamHelper18_out_float(thread float& f) {
+void _skOutParamHelper23_out_float(thread float& f) {
     float _var0;
     out_float(_var0);
     f = _var0;
 }
 void out_float2(thread float2& v);
-void _skOutParamHelper19_out_float2(thread float2& f2) {
+void _skOutParamHelper24_out_float2(thread float2& f2) {
     float2 _var0;
     out_float2(_var0);
     f2 = _var0;
 }
 void out_float3(thread float3& v);
-void _skOutParamHelper20_out_float3(thread float3& f3) {
+void _skOutParamHelper25_out_float3(thread float3& f3) {
     float3 _var0;
     out_float3(_var0);
     f3 = _var0;
 }
 void out_float4(thread float4& v);
-void _skOutParamHelper21_out_float4(thread float4& f4) {
+void _skOutParamHelper26_out_float4(thread float4& f4) {
     float4 _var0;
     out_float4(_var0);
     f4 = _var0;
 }
 void out_float2(thread float2& v);
-void _skOutParamHelper22_out_float2(thread float3& f3) {
+void _skOutParamHelper27_out_float2(thread float3& f3) {
     float2 _var0;
     out_float2(_var0);
     f3.xy = _var0;
 }
 void out_float(thread float& v);
-void _skOutParamHelper23_out_float(thread float2& f2) {
+void _skOutParamHelper28_out_float(thread float2& f2) {
     float _var0;
     out_float(_var0);
     f2.x = _var0;
 }
 void out_float2x2(thread float2x2& v);
-void _skOutParamHelper24_out_float2x2(thread float2x2& f2x2) {
+void _skOutParamHelper29_out_float2x2(thread float2x2& f2x2) {
     float2x2 _var0;
     out_float2x2(_var0);
     f2x2 = _var0;
 }
 void out_float3x3(thread float3x3& v);
-void _skOutParamHelper25_out_float3x3(thread float3x3& f3x3) {
+void _skOutParamHelper30_out_float3x3(thread float3x3& f3x3) {
     float3x3 _var0;
     out_float3x3(_var0);
     f3x3 = _var0;
 }
 void out_float4x4(thread float4x4& v);
-void _skOutParamHelper26_out_float4x4(thread float4x4& f4x4) {
+void _skOutParamHelper31_out_float4x4(thread float4x4& f4x4) {
     float4x4 _var0;
     out_float4x4(_var0);
     f4x4 = _var0;
 }
 void out_float(thread float& v);
-void _skOutParamHelper27_out_float(thread float2x2& f2x2) {
+void _skOutParamHelper32_out_float(thread float2x2& f2x2) {
     float _var0;
     out_float(_var0);
     f2x2[0].x = _var0;
 }
 void out_float4(thread float4& v);
-void _skOutParamHelper28_out_float4(thread float4x4& f4x4) {
+void _skOutParamHelper33_out_float4(thread float4x4& f4x4) {
     float4 _var0;
     out_float4(_var0);
     f4x4[1] = _var0;
 }
 void out_bool(thread bool& v);
-void _skOutParamHelper29_out_bool(thread bool& b) {
+void _skOutParamHelper34_out_bool(thread bool& b) {
     bool _var0;
     out_bool(_var0);
     b = _var0;
 }
 void out_bool2(thread bool2& v);
-void _skOutParamHelper30_out_bool2(thread bool2& b2) {
+void _skOutParamHelper35_out_bool2(thread bool2& b2) {
     bool2 _var0;
     out_bool2(_var0);
     b2 = _var0;
 }
 void out_bool3(thread bool3& v);
-void _skOutParamHelper31_out_bool3(thread bool3& b3) {
+void _skOutParamHelper36_out_bool3(thread bool3& b3) {
     bool3 _var0;
     out_bool3(_var0);
     b3 = _var0;
 }
 void out_bool4(thread bool4& v);
-void _skOutParamHelper32_out_bool4(thread bool4& b4) {
+void _skOutParamHelper37_out_bool4(thread bool4& b4) {
     bool4 _var0;
     out_bool4(_var0);
     b4 = _var0;
 }
 void out_bool2(thread bool2& v);
-void _skOutParamHelper33_out_bool2(thread bool4& b4) {
+void _skOutParamHelper38_out_bool2(thread bool4& b4) {
     bool2 _var0;
     out_bool2(_var0);
     b4.xw = _var0;
 }
 void out_bool(thread bool& v);
-void _skOutParamHelper34_out_bool(thread bool3& b3) {
+void _skOutParamHelper39_out_bool(thread bool3& b3) {
     bool _var0;
     out_bool(_var0);
     b3.z = _var0;
@@ -282,6 +322,10 @@
 void out_bool4(thread bool4& v) {
     v = bool4(false);
 }
+void out_pair(thread float& v1, thread float& v2) {
+    v1 = 1.0;
+    v2 = 2.0;
+}
 fragment Outputs fragmentMain(Inputs _in [[stage_in]], bool _frontFacing [[front_facing]], float4 _fragCoord [[position]]) {
     Outputs _out;
     (void)_out;
@@ -297,56 +341,62 @@
     _skOutParamHelper5_out_half2(h3);
     _skOutParamHelper6_out_half4(h4);
     _out.sk_FragColor = float4(h, h2.x, h3.x, h4.x);
+    float h1;
+    _skOutParamHelper7_out_pair(h, h1);
+    _skOutParamHelper8_out_pair(h, h);
+    _skOutParamHelper9_out_pair(h2, h2);
+    _skOutParamHelper10_out_pair(h2, h2);
+    _skOutParamHelper11_out_pair(h2, h3);
     float2x2 h2x2;
-    _skOutParamHelper7_out_half2x2(h2x2);
+    _skOutParamHelper12_out_half2x2(h2x2);
     float3x3 h3x3;
-    _skOutParamHelper8_out_half3x3(h3x3);
+    _skOutParamHelper13_out_half3x3(h3x3);
     float4x4 h4x4;
-    _skOutParamHelper9_out_half4x4(h4x4);
-    _skOutParamHelper10_out_half3(h3x3);
-    _skOutParamHelper11_out_half4(h4x4);
-    _skOutParamHelper12_out_half2(h2x2);
+    _skOutParamHelper14_out_half4x4(h4x4);
+    _skOutParamHelper15_out_half3(h3x3);
+    _skOutParamHelper16_out_half4(h4x4);
+    _skOutParamHelper17_out_half2(h2x2);
     _out.sk_FragColor = float4(h2x2[0].x, h3x3[0].x, h4x4[0].x, 1.0);
     int i;
-    _skOutParamHelper13_out_int(i);
+    _skOutParamHelper18_out_int(i);
     int2 i2;
-    _skOutParamHelper14_out_int2(i2);
+    _skOutParamHelper19_out_int2(i2);
     int3 i3;
-    _skOutParamHelper15_out_int3(i3);
+    _skOutParamHelper20_out_int3(i3);
     int4 i4;
-    _skOutParamHelper16_out_int4(i4);
-    _skOutParamHelper17_out_int3(i4);
+    _skOutParamHelper21_out_int4(i4);
+    _skOutParamHelper22_out_int3(i4);
     _out.sk_FragColor = float4(float(i), float(i2.x), float(i3.x), float(i4.x));
     float f;
-    _skOutParamHelper18_out_float(f);
+    _skOutParamHelper23_out_float(f);
     float2 f2;
-    _skOutParamHelper19_out_float2(f2);
+    _skOutParamHelper24_out_float2(f2);
     float3 f3;
-    _skOutParamHelper20_out_float3(f3);
+    _skOutParamHelper25_out_float3(f3);
     float4 f4;
-    _skOutParamHelper21_out_float4(f4);
-    _skOutParamHelper22_out_float2(f3);
-    _skOutParamHelper23_out_float(f2);
+    _skOutParamHelper26_out_float4(f4);
+    _skOutParamHelper27_out_float2(f3);
+    _skOutParamHelper28_out_float(f2);
     _out.sk_FragColor = float4(f, f2.x, f3.x, f4.x);
     float2x2 f2x2;
-    _skOutParamHelper24_out_float2x2(f2x2);
+    _skOutParamHelper29_out_float2x2(f2x2);
     float3x3 f3x3;
-    _skOutParamHelper25_out_float3x3(f3x3);
+    _skOutParamHelper30_out_float3x3(f3x3);
     float4x4 f4x4;
-    _skOutParamHelper26_out_float4x4(f4x4);
-    _skOutParamHelper27_out_float(f2x2);
-    _skOutParamHelper28_out_float4(f4x4);
+    _skOutParamHelper31_out_float4x4(f4x4);
+    _skOutParamHelper32_out_float(f2x2);
+    _skOutParamHelper33_out_float4(f4x4);
     _out.sk_FragColor = float4(f2x2[0].x, f3x3[0].x, f4x4[0].x, 1.0);
     bool b;
-    _skOutParamHelper29_out_bool(b);
+    _skOutParamHelper34_out_bool(b);
     bool2 b2;
-    _skOutParamHelper30_out_bool2(b2);
+    _skOutParamHelper35_out_bool2(b2);
     bool3 b3;
-    _skOutParamHelper31_out_bool3(b3);
+    _skOutParamHelper36_out_bool3(b3);
     bool4 b4;
-    _skOutParamHelper32_out_bool4(b4);
-    _skOutParamHelper33_out_bool2(b4);
-    _skOutParamHelper34_out_bool(b3);
+    _skOutParamHelper37_out_bool4(b4);
+    _skOutParamHelper38_out_bool2(b4);
+    _skOutParamHelper39_out_bool(b3);
     _out.sk_FragColor = float4(float(b), float(b2.x), float(b3.x), float(b4.x));
     return _out;
 }