Augmented operators: x=x+... becomes x+=

README.md

@@ -467,6 +467,29 @@ be an issue.
 
 Disable this transformation with the flag `--no-move-declarations`.
 
+### Augmented operators
+
+We use the augmented operators (e.g. `+=`) where possible.
+
+Input:
+```glsl
+spe=spe*spe;
+x=x-.5;
+a=a+(a<<3);
+a=a^a>>15;
+```
+
+Output:
+```glsl
+spe*=spe;
+x-=.5;
+a+=a<<3;
+a^=a>>15;
+```
+
+This transformation always reduces the size of the output. However, this seems
+to have negligible impact on the size after compression.
+
 ### Rename vector fields
 
 To access fields of a vector, it is possible to use `.rgba` fields, or `.xyzw`,

src/rewriter.fs

@@ -97,6 +97,9 @@ let (|Number|_|) = function
     | Float (f, _) -> Some f
     | _ -> None
 
+let augmentableOperators = set ["+"; "-"; "*"; "/"; "%"; "<<"; ">>"; "&"; "^"; "|"]
+
+
 let private simplifyOperator env = function
     | FunCall(Op "-", [Int (i1, su)]) -> Int (-i1, su)
     | FunCall(Op "-", [FunCall(Op "-", [e])]) -> e
@@ -173,6 +176,11 @@ let private simplifyOperator env = function
     // x-(y-z) -> x-y+z
     | FunCall(Op "-", [x; FunCall(Op "-", [y; z])]) ->
         FunCall(Op "+", [FunCall(Op "-", [x; y]); z]) |> env.fExpr env
+
+    // Match:  x = x + ...
+    | FunCall(Op "=", [Var x; FunCall(Op op, [Var y; e])])
+            when x.Name = y.Name && augmentableOperators.Contains op ->
+        FunCall(Op (op + "="), [Var x; e])
     | e -> e
 
 

tests/commands.txt

@@ -21,6 +21,7 @@
 --no-renaming --no-inlining --format indented -o tests/unit/pi.frag.expected tests/unit/pi.frag
 --no-renaming --no-inlining --format indented -o tests/unit/vectors.frag.expected tests/unit/vectors.frag
 --no-renaming --format indented -o tests/unit/deadcode.frag.expected tests/unit/deadcode.frag
+--no-renaming --no-inlining --format indented -o tests/unit/augmented.frag.expected tests/unit/augmented.frag
 
 # Inlining unit tests
 

tests/compression_results.log

@@ -1,17 +1,17 @@
 from-the-seas-to-the-stars.frag          14347 => 2353.607
-the_real_party_is_in_your_pocket.frag    12214 => 1829.362
+the_real_party_is_in_your_pocket.frag    12213 => 1829.362
 ed-209.frag                               7899 => 1359.091
 valley_ball.glsl                          4419 =>  896.357
 lunaquatic.frag                           5232 => 1056.700
-slisesix.frag                             4546 =>  957.481
+slisesix.frag                             4543 =>  958.065
 yx_long_way_from_home.frag                2993 =>  614.607
 oscars_chair.frag                         4649 =>  982.393
-kinder_painter.frag                       2901 =>  456.603
+kinder_painter.frag                       2894 =>  456.030
 ohanami.frag                              3293 =>  746.366
-terrarium.frag                            3646 =>  748.815
+terrarium.frag                            3633 =>  749.292
 leizex.frag                               2308 =>  515.785
 elevated.hlsl                             3406 =>  611.302
 buoy.frag                                 4237 =>  630.724
 orchard.frag                              5618 => 1058.054
-robin.frag                                6298 => 1067.719
-Total: 88006 => 15884.964
+robin.frag                                6294 => 1066.421
+Total: 87978 => 15884.156

tests/real/kinder_painter.expected

@@ -54,12 +54,12 @@
  "{"
    "vec3 nor;"
    "if(col.w>2.5)"
-     "nor.xz=inter.xz-obj.xz,nor.y=0.,nor=nor/obj.w,uv=vec2(nor.x,inter.y);"
+     "nor.xz=inter.xz-obj.xz,nor.y=0.,nor/=obj.w,uv=vec2(nor.x,inter.y);"
    "else"
      " if(col.w>1.5)"
        "nor=obj.xyz,uv=inter.xz*.2;"
      "else"
-       " nor=inter-obj.xyz,nor=nor/obj.w,uv=nor.xy;"
+       " nor=inter-obj.xyz,nor/=obj.w,uv=nor.xy;"
    "return nor;"
  "}"
  "vec4 cmov(vec4 a,vec4 b,bool cond)"
@@ -131,8 +131,8 @@
    "ref.xyz=reflect(rd,nor);"
    "spe=dot(ref.xyz,luz.xyz);"
    "spe=max(spe,0.);"
-   "spe=spe*spe;"
-   "spe=spe*spe;"
+   "spe*=spe;"
+   "spe*=spe;"
    "if(intersectShadow(inter,luz.xyz,luz.w))"
      "dif=0.;"
    "col*=texture2D(tex0,uv);"
@@ -141,8 +141,8 @@
    "dif=dot(nor,-rd);"
    "ref.w=dif;"
    "dif=1.-dif*dif;"
-   "dif=dif*dif;"
-   "col=col+.35*vec4(dif);"
+   "dif*=dif;"
+   "col+=.35*vec4(dif);"
    "return col;"
  "}"
  "void main()"
@@ -174,7 +174,7 @@
    "luz.xyz=luz.xyz/luz.w;"
    "col=basicShade(inter,obj,col,rd,luz,ref);"
    "tmin=intersect(inter,ref.xyz,obj,col2);"
-   "inter=inter+ref.xyz*tmin;"
+   "inter+=ref.xyz*tmin;"
    "luz.xyz=vec3(0,1.5,-1)-inter;"
    "luz.w=length(luz.xyz);"
    "luz.xyz=luz.xyz/luz.w;"

tests/real/mandelbulb.expected

@@ -28,11 +28,11 @@ const char *mandelbulb_frag =
    "for(int t=1;t<7;t++)"
      "{"
        "\n#if 0\n"
-       "float z=sqrt(dot(i,i)),c=acos(i.y/z),o=atan(i.x,i.z);"
+       "float z=sqrt(dot(i,i)),o=acos(i.y/z),c=atan(i.x,i.z);"
        "z=pow(z,8.);"
-       "c=c*8.;"
-       "o=o*8.;"
-       "i=v+z*vec3(sin(c)*sin(o),cos(c),sin(c)*cos(o));"
+       "o*=8.;"
+       "c*=8.;"
+       "i=v+z*vec3(sin(o)*sin(c),cos(o),sin(o)*cos(c));"
        "\n#else\n"
        "float s=i.x,d=s*s,n=d*d,m=i.y,l=m*m,p=i.z,w=p*p,r=w*w,g=d+w,a=inversesqrt(g*g*g*g*g*g*g),u=n+l*l+r-6.*l*w-6.*d*l+2.*w*d,q=d-l+w;"
        "i.x=v.x+64.*s*m*p*(d-w)*q*(n-6.*d*w+r)*u*a;"
@@ -100,7 +100,7 @@ const char *mandelbulb_frag =
      "{"
        "vec3 m=c+u*s,a;"
        "float q=clamp(.2+.8*dot(f,n),0.,1.),b,F,C;"
-       "q=q*q;"
+       "q*=q;"
        "b=clamp(.3+.7*dot(o,n),0.,1.);"
        "F=clamp(1.25*g.w-.4,0.,1.);"
        "F=F*F*.5+.5*F;"

tests/real/slisesix.frag.expected

@@ -30,7 +30,7 @@ float techo(float x,float y)
   y=1.-y;
   if(x<.1||x>.9)
     return y;
-  x=x-.5;
+  x-=.5;
   return-(sqrt(x*x+y*y)-.4);
 }
 float distToBox(vec3 p,vec3 abc)
@@ -190,7 +190,7 @@ void main()
       lig=vec3(.5-pos.x,.8-pos.y,1.5-pos.z);
       llig=dot(lig,lig);
       im=inversesqrt(llig);
-      lig=lig*im;
+      lig*=im;
       dif=dot(nor,lig);
       if(matID==4)
         dif=.5+.5*dif;
@@ -264,7 +264,7 @@ void main()
         }
       dif*=clamp((so-.4)*1.5,0.,1.);
       rgb=vec3(spe)+rgb*(ao*vec3(.25,.3,.35)+dif*vec3(1.95,1.65,1.05));
-      rgb=rgb*exp2(-.4*t);
+      rgb*=exp2(-.4*t);
     }
   rgb=(sqrt(rgb)*.7+.3*rgb)*vec3(.83,1,.83)*1.2;
   rgb*=.25+.75*clamp(.6*abs(pixel.x-1.)*abs(pixel.x+1.),0.,1.);

tests/real/terrarium.frag.expected

@@ -10,19 +10,19 @@ float time=float(m)/44100.;
 int IH(int a)
 {
   a=a^61^a>>16;
-  a=a+(a<<3);
-  a=a^a>>4;
-  a=a*668265261;
-  a=a^a>>15;
+  a+=a<<3;
+  a^=a>>4;
+  a*=668265261;
+  a^=a>>15;
   return a;
 }
 float H(int a)
 {
   a=a^61^a>>16;
-  a=a+(a<<3);
-  a=a^a>>4;
-  a=a*668265261;
-  a=a^a>>15;
+  a+=a<<3;
+  a^=a>>4;
+  a*=668265261;
+  a^=a>>15;
   return float(a)/2147483647;
 }
 vec2 rand2(int a)
@@ -131,7 +131,7 @@ void main()
       u=sqrt(1-u*u);
       x=vec3(cos(phi)*u,sin(phi)*u,w.y*2-1)*pow(w.z,1./3)*3;
       q=mix(q,q+x*.5,.1*pow(H(seed),16.));
-      q=q+x*.2*(1.-min(time/30.,1.)+max(0.,time-130)/20.);
+      q+=x*.2*(1.-min(time/30.,1.)+max(0.,time-130)/20.);
       u=time/8.+199.*step(.5,H(int(floor(time/60.*64.))))*step(60.,time)*step(time,120);
       q.xy=mat2(cos(u),sin(u),-sin(u),cos(u))*q.xy;
       u=.4+time/9.;

tests/real/the_real_party_is_in_your_pocket.frag.expected

@@ -288,7 +288,7 @@ const char *the_real_party_is_in_your_pocket_frag =
                "break;"
              "k=.02;"
              "if(m()>k)"
-               "l=c-z*2e-4*-sign(v.z),v=v+(vec3(m(),m(),m())-.5)*.1;"
+               "l=c-z*2e-4*-sign(v.z),v+=(vec3(m(),m(),m())-.5)*.1;"
              "else"
                " l=c+z*2e-4,v=reflect(v,z)+(vec3(m(),m(),m())-.5)*.3;"
            "}"

tests/unit/augmented.frag

@@ -0,0 +1,13 @@
+int foo(int x, int y) {
+    int a=x;
+    a=a+x;
+    a=a*y;
+    a=a>>x;
+    a=a^y;
+    a=a|y;
+    return a;
+}
+
+void main() {
+    foo(0, 0);
+}

tests/unit/augmented.frag.expected

@@ -0,0 +1,14 @@
+int foo(int x,int y)
+{
+  int a=x;
+  a+=x;
+  a*=y;
+  a>>=x;
+  a^=y;
+  a|=y;
+  return a;
+}
+void main()
+{
+  foo(0,0);
+}