Add loop optimizations for windows builds.

build/config/compiler/BUILD.gn

@@ -1896,6 +1896,32 @@ if (is_win) {
     ]
   }
   common_optimize_on_ldflags = []
+
+  common_optimize_on_cflags += [
+    "-mllvm", "-extra-vectorizer-passes",
+    "-mllvm", "-enable-cond-stores-vec",
+    "-mllvm", "-slp-vectorize-hor-store",
+    "-mllvm", "-enable-loopinterchange",
+    "-mllvm", "-enable-loop-distribute",
+    "-mllvm", "-enable-unroll-and-jam",
+    "-mllvm", "-enable-loop-flatten",
+    "-mllvm", "-interleave-small-loop-scalar-reduction",
+    "-mllvm", "-unroll-runtime-multi-exit",
+    "-mllvm", "-aggressive-ext-opt",
+  ]
+
+  common_optimize_on_ldflags += [
+    "-mllvm:-extra-vectorizer-passes",
+    "-mllvm:-enable-cond-stores-vec",
+    "-mllvm:-slp-vectorize-hor-store",
+    "-mllvm:-enable-loopinterchange",
+    "-mllvm:-enable-loop-distribute",
+    "-mllvm:-enable-unroll-and-jam",
+    "-mllvm:-enable-loop-flatten",
+    "-mllvm:-interleave-small-loop-scalar-reduction",
+    "-mllvm:-unroll-runtime-multi-exit",
+    "-mllvm:-aggressive-ext-opt",
+  ]
 
   # /OPT:ICF is not desirable in Debug builds, since code-folding can result in
   # misleading symbols in stack traces.
@@ -2104,7 +2130,7 @@ config("optimize_max") {
     if (is_win) {
       # Favor speed over size, /O2 must be before the common flags.
       # /O2 implies /Ot, /Oi, and /GF.
-      cflags = [ "/O2" ] + common_optimize_on_cflags
+      cflags = [ "-Xclang", "-O3" ] + common_optimize_on_cflags
     } else if (optimize_for_fuzzing) {
       cflags = [ "-O1" ] + common_optimize_on_cflags
     } else {
@@ -2137,7 +2163,7 @@ config("optimize_speed") {
     if (is_win) {
       # Favor speed over size, /O2 must be before the common flags.
       # /O2 implies /Ot, /Oi, and /GF.
-      cflags = [ "/O2" ] + common_optimize_on_cflags
+      cflags = [ "-Xclang", "-O3" ] + common_optimize_on_cflags
     } else if (optimize_for_fuzzing) {
       cflags = [ "-O1" ] + common_optimize_on_cflags
     } else {