Inlining: automatically inline trivial values

This is a conservative first step. Inline variables only if there value is a constant (it doesn't depend on another variable).

src/ast.fs

@@ -4,10 +4,13 @@ open Options.Globals
 
 type Ident(name: string) =
     let mutable newName = name
+    let mutable inlined = newName.StartsWith("i_")
+
     member this.Name = newName
     member this.OldName = name
     member this.Rename(n) = newName <- n
-    member this.MustBeInlined = this.Name.StartsWith("i_")
+    member this.ToBeInlined = inlined
+    member this.Inline() = inlined <- true
 
      // Real identifiers cannot start with a digit, but the temporary ids of the rename pass are numbers.
     member this.IsUniqueId = System.Char.IsDigit this.Name.[0]

src/rewriter.fs

@@ -57,7 +57,7 @@ let private stripSpaces str =
     result.ToString()
 
 
-let private declsNotToInline (d: Ast.DeclElt list) = d |> List.filter (fun x -> not x.name.MustBeInlined)
+let private declsNotToInline (d: Ast.DeclElt list) = d |> List.filter (fun x -> not x.name.ToBeInlined)
 
 let private bool = function
     | true -> Var (Ident "true") // Int (1, "")
@@ -132,9 +132,9 @@ let rec private simplifyExpr env = function
 
     | Dot(e, field) when options.canonicalFieldNames <> "" -> Dot(e, renameField field)
 
-    | Var s as e when s.MustBeInlined ->
+    | Var s as e ->
         match env.vars.TryFind s.Name with
-        | Some (_, {init = Some init}) -> init |> mapExpr env
+        | Some (_, {name = id; init = Some init}) when id.ToBeInlined -> init |> mapExpr env
         | _ -> e
 
     // pi is acos(-1), pi/2 is acos(0)
@@ -165,6 +165,56 @@ let private rwTypeSpec = function
 let rwType (ty: Type) =
     makeType (rwTypeSpec ty.name) (Option.map stripSpaces ty.typeQ)
 
+// Return the list of variables used in the statements, with the number of references.
+let collectReferences stmtList =
+    let count = Dictionary<string, int>()
+    let collectLocalUses _ = function
+        | Var v as e ->
+            match count.TryGetValue(v.Name) with
+            | true, n -> count.[v.Name] <- n + 1
+            | false, _ -> count.[v.Name] <- 1
+            e
+        | e -> e
+    for expr in stmtList do
+        mapStmt (mapEnv collectLocalUses id) expr |> ignore
+    count
+
+// Mark variables as inlinable when possible.
+// For now, only mark a variable when:
+//  - the variable is used only once in the current block
+//  - the variable is not used in a sub-block (e.g. inside a loop)
+//  - the init value is trivial (doesn't depend on a variable)
+let findInlinable block =
+    // Variables that are defined in this scope.
+    let localDefs = Dictionary<string, Ident>()
+    // List of expressions in the current block. Do not look in sub-blocks.
+    let mutable localExpr = []
+    for stmt: Stmt in block do
+        match stmt with
+        | Decl (_, li) ->
+            for def in li do
+                // can only inline if it has a value
+                match def.init with
+                | None -> ()
+                | Some init ->
+                    localExpr <- init :: localExpr
+                    // Inline only if the init value doesn't depend on other variables.
+                    let deps = collectReferences [Expr init]
+                    if deps.Count = 0 then
+                        localDefs.[def.name.Name] <- def.name
+        | Expr e
+        | Jump (_, Some e) -> localExpr <- e :: localExpr
+        | Verbatim _ | Jump (_, None) | Block _ | If _| ForE _ | ForD _ | While _ | DoWhile _ -> ()
+
+    let localReferences = collectReferences (List.map Expr localExpr)
+    let allReferences = collectReferences block
+
+    for def in localDefs do
+        if not def.Value.ToBeInlined then
+            match localReferences.TryGetValue(def.Key), allReferences.TryGetValue(def.Key) with
+            | (true, 1), (true, 1) -> def.Value.Inline()
+            | _ -> ()
+
 let private simplifyStmt = function
     | Block [] as e -> e
     | Block b ->
@@ -174,6 +224,8 @@ let private simplifyStmt = function
 
         // Remove inner empty blocks
         let b = b |> List.filter (function Block [] | Decl (_, []) -> false | _ -> true)
+
+        findInlinable b
 
         // Try to remove blocks by using the comma operator
         let returnExp = b |> Seq.tryPick (function Jump(JumpKeyword.Return, e) -> e | _ -> None)
@@ -216,6 +268,8 @@ let simplify li =
     li
     |> reorderTopLevel
     |> mapTopLevel (mapEnv simplifyExpr simplifyStmt)
+    // A second pass, because some variables might now be inlinable.
+    |> mapTopLevel (mapEnv simplifyExpr simplifyStmt)
     |> List.map (function
         | TLDecl (ty, li) -> TLDecl (rwType ty, declsNotToInline li)
         | TLVerbatim s -> TLVerbatim (stripSpaces s)

tests/real/yx_long_way_from_home.frag.expected

@@ -64,12 +64,11 @@ const char *yx_long_way_from_home_frag =
        "m.y+=sin(m.x*2.)*.05;"
        "m.y-=length(sin(m.xz*.5))*.1;"
        "m.z+=sin(m.x*.5)*.5;"
-       "float y=.03;"
        "m.z+=step(.5,mod(m.x,1.))*.3-.15;"
        "m.x=mod(m.x,.5)-.25;"
-       "float l=t(m.xz),z=smoothstep(.1,.13,l);"
-       "m.y+=.1-z*y;"
-       "m.y-=smoothstep(.05,0.,abs(l-.16))*.004;"
+       "float y=t(m.xz),z=smoothstep(.1,.13,y);"
+       "m.y+=.1-z*.03;"
+       "m.y-=smoothstep(.05,0.,abs(y-.16))*.004;"
        "m.y-=(1.-z)*.01*h(m.xz);"
      "}"
    "m.y-=smoothstep(2.,0.,length(n.xz+vec2(-1.5,3.5)))*.2;"
@@ -91,15 +90,15 @@ const char *yx_long_way_from_home_frag =
    "vec3 f=cross(vec3(-1,-1,-1),v);"
    "return f;"
  "}"
- "vec3 e(vec3 v,float m)"
+ "vec3 e(vec3 v,float y)"
  "{"
    "v=normalize(v);"
-   "vec3 y=normalize(p(v)),f=normalize(cross(v,y));"
+   "vec3 f=normalize(p(v)),m=normalize(cross(v,f));"
    "vec2 n=i;"
    "n.x=n.x*2.*pi;"
-   "n.y=pow(n.y,1./(m+1.));"
+   "n.y=pow(n.y,1./(y+1.));"
    "float x=sqrt(1.-n.y*n.y);"
-   "return cos(n.x)*x*y+sin(n.x)*x*f+n.y*v;"
+   "return cos(n.x)*x*f+sin(n.x)*x*m+n.y*v;"
  "}"
  "vec3 x(vec3 v)"
  "{"
@@ -145,39 +144,38 @@ const char *yx_long_way_from_home_frag =
  "}"
  "vec3 h(vec3 v,vec3 m)"
  "{"
-   "float x=.65,z=.18;"
-   "vec3 y=normalize(vec3((x-.5)*2.,z*2.,-1));"
-   "const float n=.0001;"
-   "const vec3 c=vec3(1.,.6,.2)*2.;"
-   "vec3 r=vec3(1),o=vec3(0);"
-   "for(int g=0;g<10;++g)"
+   "vec3 x=normalize(vec3(.3,.36,-1));"
+   "const float y=.0001;"
+   "const vec3 n=vec3(1.,.6,.2)*2.;"
+   "vec3 z=vec3(1),c=vec3(0);"
+   "for(int r=0;r<10;++r)"
      "{"
-       "vec3 a,p;"
-       "float t;"
-       "if(d(v,m,a,p,t))"
+       "vec3 a,o;"
+       "float p;"
+       "if(d(v,m,a,o,p))"
          "{"
-           "float k=1.;"
-           "vec3 b=vec3(1);"
+           "float t=1.;"
+           "vec3 g=vec3(1);"
            "if(f==1)"
-             "b=vec3(.7);"
-           "k*=k;"
+             "g=vec3(.7);"
+           "t*=t;"
            "{"
-             "v=a+p*.002;"
-             "vec3 h=reflect(m,p),u=e(p,1.);"
-             "m=normalize(mix(h,u,k));"
-             "r*=b;"
+             "v=a+o*.002;"
+             "vec3 h=reflect(m,o),u=e(o,1.);"
+             "m=normalize(mix(h,u,t));"
+             "z*=g;"
            "}"
-           "vec3 h=d(y,n);"
-           "float u=dot(p,h);"
-           "vec3 S,R;"
-           "float B;"
-           "if(u>0.&&!d(a+p*.002,h,S,R,B))"
-             "o+=r*u*c;"
+           "vec3 h=d(x,y);"
+           "float u=dot(o,h);"
+           "vec3 b,k;"
+           "float S;"
+           "if(u>0.&&!d(a+o*.002,h,b,k,S))"
+             "c+=z*u*n;"
            "i=s(i.y);"
          "}"
        "else"
-         " if(abs(t)>.1)"
-           "return o+l(m)*r;"
+         " if(abs(p)>.1)"
+           "return c+l(m)*z;"
          "else"
            " break;"
      "}"
@@ -194,26 +192,26 @@ const char *yx_long_way_from_home_frag =
  "void main()"
  "{"
    "vec2 v=gl_FragCoord.xy/iResolution.xy-.5;"
-   "float m=iTime+(v.x+iResolution.x*v.y)*1.51269;"
-   "i=s(m);"
+   "float y=iTime+(v.x+iResolution.x*v.y)*1.51269;"
+   "i=s(y);"
    "v+=(i-.5)/iResolution.xy;"
    "v.x*=iResolution.x/iResolution.y;"
-   "const vec3 f=vec3(-4,2,3),y=vec3(0,0,0);"
-   "const float x=distance(f,y);"
+   "const vec3 m=vec3(-4,2,3),f=vec3(0,0,0);"
+   "const float x=distance(m,f);"
    "const vec2 z=vec2(1,2)*.015;"
    "vec3 c=vec3(0),r=normalize(vec3(v,2.));"
    "vec2 t=d();"
    "c.xy+=t*z;"
    "r.xy-=t*z*r.z/x;"
-   "vec3 l=y-f;"
-   "float p=-atan(l.y,length(l.xz)),a=-atan(l.x,l.z);"
+   "vec3 l=f-m;"
+   "float p=-atan(l.y,length(l.xz)),o=-atan(l.x,l.z);"
    "c.yz*=n(p);"
    "r.yz*=n(p);"
-   "c.xz*=n(a);"
-   "r.xz*=n(a);"
-   "c+=f;"
-   "vec4 u=vec4(h(c,r),1);"
-   "gl_FragColor=!isnan(u.x)&&u.x>=0.?u:vec4(0);"
+   "c.xz*=n(o);"
+   "r.xz*=n(o);"
+   "c+=m;"
+   "vec4 a=vec4(h(c,r),1);"
+   "gl_FragColor=!isnan(a.x)&&a.x>=0.?a:vec4(0);"
  "}";
 
 #endif // YX_LONG_WAY_FROM_HOME_FRAG_EXPECTED_

tests/unit/function_comma.expected

@@ -11,8 +11,8 @@ const char *function_comma_frag =
  "}"
  "float foo()"
  "{"
-   "float a=1.2,b=2.3;"
-   "return min((a=1.,b+a),0.);"
+   "float a=1.2;"
+   "return min((a=1.,2.3+a),0.);"
  "}"
  "float bar()"
  "{"

tests/unit/inline.expected

@@ -10,3 +10,8 @@ int vars(int arg,int arg2)
 {
   return arg*(arg+arg2);
 }
+int arithmetic2()
+{
+  int a=2,c=a+3;
+  return 4*a*c;
+}

tests/unit/inline.frag

@@ -20,3 +20,11 @@ int vars(int arg, int arg2)
   int i_c = i_a + i_b;
   return i_a * i_c;
 }
+
+int arithmetic2()
+{
+  int a = 2;
+  int b = 3;
+  int c = a + b;
+  return 4 * a * c;
+}

tests/unit/inout.expected

@@ -7,22 +7,20 @@ in vec3 c,v;
 out vec4 o;
 void main()
 {
-  vec3 n=normalize(v),f=normalize(c),u=vec3(.1,.2,.3),z=vec3(.5,.5,.5);
-  float x=1.5;
-  vec3 p=texture(e,reflect(-n,f)).xyz,d=texture(e,refract(-n,f,1./x)).xyz,s=mix(u*d,p,.1);
-  o=vec4(s,1.);
+  vec3 l=normalize(v),u=normalize(c),f=vec3(.1,.2,.3),z=vec3(.5,.5,.5),x=texture(e,reflect(-l,u)).xyz,p=texture(e,refract(-l,u,1./1.5)).xyz,d=mix(f*p,x,.1);
+  o=vec4(d,1.);
 }
-vec3 r(vec3 z,vec3 n,vec3 C)
+vec3 r(vec3 z,vec3 l,vec3 s)
 {
-  float y=1.-clamp(dot(n,C),0.,1.);
-  return y*y*y*y*y*(1.-z)+z;
+  float C=1.-clamp(dot(l,s),0.,1.);
+  return C*C*C*C*C*(1.-z)+z;
 }
-vec3 r(vec3 n,vec3 w,vec3 f,vec3 u,vec3 z,float b)
+vec3 r(vec3 l,vec3 y,vec3 u,vec3 f,vec3 z,float w)
 {
-  vec3 C=normalize(n+w);
-  float Z=1.+2048.*(1.-b)*(1.-b);
-  vec3 Y=u,X=vec3(pow(clamp(dot(C,f),0.,1.),Z)*(Z+4.)/8.),W=r(z,n,C);
-  return mix(Y,X,W);
+  vec3 s=normalize(l+y);
+  float b=1.+2048.*(1.-w)*(1.-w);
+  vec3 Z=f,Y=vec3(pow(clamp(dot(s,u),0.,1.),b)*(b+4.)/8.),X=r(z,l,s);
+  return mix(Z,Y,X);
 }
 
 // tests/unit/inout2.frag
@@ -31,25 +29,23 @@ vec3 r(vec3 n,vec3 w,vec3 f,vec3 u,vec3 z,float b)
 
 uniform samplerCube e;
 uniform float t;
-uniform vec3 a,m,l,i;
+uniform vec3 m,i,a,n;
 in vec3 c,v;
 out vec4 o;
-vec3 r(vec3 z,vec3 n,vec3 C)
+vec3 r(vec3 z,vec3 l,vec3 s)
 {
-  float y=1.-clamp(dot(n,C),0.,1.);
-  return y*y*y*y*y*(1.-z)+z;
+  float C=1.-clamp(dot(l,s),0.,1.);
+  return C*C*C*C*C*(1.-z)+z;
 }
 void main()
 {
-  vec3 n=normalize(v),f=normalize(c),u=m,z=i;
-  float V=.5;
-  vec3 s=l+mix(u*a,a,V);
-  o=vec4(s,1.);
+  vec3 l=normalize(v),u=normalize(c),f=i,z=n,d=a+mix(f*m,m,.5);
+  o=vec4(d,1.);
 }
-vec3 r(vec3 n,vec3 w,vec3 f,vec3 u,vec3 z,float b)
+vec3 r(vec3 l,vec3 y,vec3 u,vec3 f,vec3 z,float w)
 {
-  vec3 C=normalize(n+w);
-  float Z=1.+2048.*(1.-b)*(1.-b);
-  vec3 Y=u,X=vec3(pow(clamp(dot(C,f),0.,1.),Z)*(Z+4.)/8.),W=r(z,n,C);
-  return mix(Y,X,W);
+  vec3 s=normalize(l+y);
+  float b=1.+2048.*(1.-w)*(1.-w);
+  vec3 Z=f,Y=vec3(pow(clamp(dot(s,u),0.,1.),b)*(b+4.)/8.),X=r(z,l,s);
+  return mix(Z,Y,X);
 }

tests/unit/macros.expected

@@ -23,8 +23,8 @@ const char *macros_frag =
  "#define p$\n"
  "int t()"
  "{"
-   "int t=1,r=2,u=3,Z=4,Y=5,X=6,W=7,V=8,U=9,T=10,S=11,R=12;"
-   "return t+Y+R;"
+   "int t=2,r=3,u=4,Z=6,Y=7,X=8,W=9,V=10,U=11;"
+   "return 18;"
  "}";
 
 #endif // MACROS_EXPECTED_

tests/unit/many_variables.expected

@@ -6,12 +6,12 @@
 "int t(float t,float o,float l,float f,float a,float n,float i,float r,float u,float e,float Z,float Y)"
  "{"
    "float X=t,W=o,V=l,U=f,T=a,S=n;"
-   "int R=1,Q=2,P=3,O=4,N=5,M=6,L=7,K=8;"
-   "float J=i,I=r,H=u,G=e,F=Z,E=Y;"
-   "int D=1,C=2,B=3,A=4,z=5,y=6,x=7,w=8;"
-   "float v=0.;"
-   "int s=1,q=2,p=3,m=4,k=5,j=6,h=7,g=8;"
-   "float d=0.;"
-   "int c=1,b=2,at=3,ab=4,ac=5,ad=6,ag=7,ah=8;"
-   "return K+w+g+ah;"
+   "int R=1,Q=2,P=3,O=4,N=5,M=6,L=7;"
+   "float K=i,J=r,I=u,H=e,G=Z,F=Y;"
+   "int E=1,D=2,C=3,B=4,A=5,z=6,y=7;"
+   "float x=0.;"
+   "int w=1,v=2,s=3,q=4,p=5,m=6,k=7;"
+   "float j=0.;"
+   "int h=1,g=2,d=3,c=4,b=5,at=6,ab=7;"
+   "return 32;"
  "}",