Augmentable operators optimization: * is not always commutative (#372)

This is a fix to an issue found in #369.
Thanks to @therontarigo!

src/rewriter.fs

@@ -211,14 +211,14 @@ module private RewriterImpl =
 
         // a=a;  ->  a
         | FunCall(Op "=", [Var x; Var y]) when x.Name = y.Name -> Var y
-        // Match:  x = x + ...
+        // x=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])
 
-        // Match:  x = ... + x
-        // works only if the operator is commutative
-        | FunCall(Op "=", [Var x; FunCall(Op ("+"|"*"|"&"|"^"|"|" as op), [e; Var y])])
+        // x=...+x  ->  x+=...
+        // Works only if the operator is commutative. * is not commutative with vectors and matrices.
+        | FunCall(Op "=", [Var x; FunCall(Op ("+"|"&"|"^"|"|" as op), [e; Var y])])
                 when x.Name = y.Name ->
             FunCall(Op (op + "="), [Var x; e])
 
@@ -370,12 +370,12 @@ module private RewriterImpl =
 
         List.collect replacements stmts
 
-    // Squeeze declarations: "float a=2.; float b;" => "float a=2.,b;"
+    // Squeeze declarations: "float a=2.; float b;"  ->  "float a=2.,b;"
     let rec squeezeConsecutiveDeclarations = function
         | []-> []
         | Decl(ty1, li1) :: Decl(ty2, li2) :: l when ty1 = ty2 ->
             squeezeConsecutiveDeclarations (Decl(ty1, li1 @ li2) :: l)
-        // int a=2; for (int b=3; ...) -> int a=2, b=3; for (; ...)
+        // int a=2; for (int b=3; ...)  ->  int a=2, b=3; for (; ...)
         | Decl(ty1, li1) :: ForD((ty2, li2), cond, inc, body) :: l when ty1 = ty2 ->
             squeezeConsecutiveDeclarations (Decl(ty1, li1 @ li2) :: ForE(None, cond, inc, body) :: l)
         | e::l -> e :: squeezeConsecutiveDeclarations l

tests/compression_results.log

@@ -1,24 +1,24 @@
 clod.frag...                              8836 => 1515.830
-mouton/mouton.vert...                    16951 => 2447.462
-audio-flight-v2.frag                      4509 =>  881.311
+mouton/mouton.vert...                    16952 => 2447.464
+audio-flight-v2.frag                      4510 =>  881.310
 buoy.frag                                 4051 =>  607.428
 controllable-machinery.frag               7703 => 1216.907
 ed-209.frag                               7697 => 1340.743
 elevated.hlsl                             3400 =>  602.269
 endeavour.frag                            2584 =>  532.679
-from-the-seas-to-the-stars.frag          14250 => 2308.842
+from-the-seas-to-the-stars.frag          14251 => 2308.886
 frozen-wasteland.frag                     4566 =>  806.475
 kinder_painter.frag                       2847 =>  442.771
 leizex.frag                               2270 =>  510.375
 lunaquatic.frag                           5234 => 1043.382
 mandelbulb.frag                           2342 =>  537.655
-ohanami.frag                              3255 =>  723.732
-orchard.frag                              5505 => 1027.273
+ohanami.frag                              3256 =>  723.324
+orchard.frag                              5506 => 1027.274
 oscars_chair.frag                         4651 =>  986.364
 robin.frag                                6254 => 1047.419
 slisesix.frag                             4549 =>  913.642
 terrarium.frag                            3593 =>  741.557
 the_real_party_is_in_your_pocket.frag    12087 => 1780.714
 valley_ball.glsl                          4307 =>  881.820
 yx_long_way_from_home.frag                2942 =>  598.650
-Total: 134383 => 23495.298
+Total: 134388 => 23494.936

tests/real/audio-flight-v2.frag.expected

@@ -188,7 +188,7 @@ vec2 marcher(vec3 ro,vec3 rd)
 }
 vec3 normal(vec3 p,float t)
 {
-  t*=MINDIST;
+  t=MINDIST*t;
   vec2 h=vec2(1,-1)*.5773;
   return normalize(h.xyy*map(p+h.xyy*t,0.).x+h.yyx*map(p+h.yyx*t,0.).x+h.yxy*map(p+h.yxy*t,0.).x+h.xxx*map(p+h.xxx*t,0.).x);
 }

tests/real/from-the-seas-to-the-stars.frag.expected

@@ -760,7 +760,7 @@ void main()
       p.y+=.5;
       vec3 r=normalize(camtarget-campos),s=normalize(cross(vec3(0,1,0),r)),t=cross(s,r);
       p-=campos;
-      p*=transpose(mat3(s,-t,r));
+      p=transpose(mat3(s,-t,r))*p;
       p.xy*=rotmat(sin(time/2)*.05*cameraroll+cameraroll2);
       p.y+=(fbm(vec2(time/16))-.5)*.1*cameraroll;
       p.x+=(fbm(vec2(time/14+10))-.5)*.1*cameraroll;

tests/real/mouton/mouton.expected

@@ -767,7 +767,7 @@ const char *mouton_frag =
        "b=mix(b,mix(mix(vec3(1,.5,0),vec3(.8,.5,1),(cos(Y*5.+t*5.)*.5+.5)*a.y),vec3(1),smoothstep(-Y,Y,q)),a.x);"
      "}"
    "l=vec2(abs(f.x*5.-.35)-1.8,f.y*5.-1.4);"
-   "l*=E(t*5.);"
+   "l=E(t*5.)*l;"
    "G=(1.4+.2*sin(t*20.))*smoothstep(.5,1.,a.x);"
    "O=J(l,G);"
    "P=mix(vec3(1,.6,0),vec3(1,.2,0),smoothstep(-.1,.6,J(l,G*.5)))*1.3;"

tests/real/ohanami.frag.expected

@@ -58,7 +58,7 @@ void main()
       if(ti==10)
         ro.y+=2;
       vec3 w=normalize(vec3(0,1.3,0)-ro),u=normalize(cross(w,vec3(0,1,0)));
-      rd*=mat3(u,normalize(cross(w,-u)),w);
+      rd=mat3(u,normalize(cross(w,-u)),w)*rd;
       gl_FragColor.xyz=vec3(.8,.8,1)/6;
       float t=0.,d=0.;
       for(int i=0;i<100;++i)

tests/real/orchard.frag.expected

@@ -279,7 +279,7 @@ void mainImage(out vec4 fragColour,vec2 fragCoord)
 #endif
 
   vec3 seedDir=normalize(vec3(0,0,1));
-  seedDir*=viewMat(uv.y+sin(time*.5)*.4,uv.x+time*.5);
+  seedDir=viewMat(uv.y+sin(time*.5)*.4,uv.x+time*.5)*seedDir;
   vec3 rd=seedDir,col=vec3(0),sky=mix(vec3(FOG_COLOUR),vec3(0,.4,.6),abs(rd.y));
   float alpha=marchScene(camera,rd,fragCoord);
   vec4 mat;

tests/unit/inline.no.expected

@@ -4,7 +4,7 @@ float result;
 void main()
 {
   float x=.5;
-  x*=.6*x;
+  x=.6*x*x;
   result=x;
 }
 int arithmetic()