diff --git a/src/alloy/backend/x64/lowering/lowering_sequences.cc b/src/alloy/backend/x64/lowering/lowering_sequences.cc
index 8f3b2599f..45bbaa32e 100644
--- a/src/alloy/backend/x64/lowering/lowering_sequences.cc
+++ b/src/alloy/backend/x64/lowering/lowering_sequences.cc
@@ -2456,11 +2456,11 @@ table->AddSequence(OPCODE_NOT, [](X64Emitter& e, Instr*& i) {
   } else if (IsVecType(i->dest->type)) {
     XmmUnaryOp(e, i, i->flags, [](X64Emitter& e, Instr& i, const Xmm& dest, const Xmm& src) {
       // dest_src ^= 0xFFFF...
-      e.cmpeqps(e.xmm0, e.xmm0);
       if (dest != src) {
         e.movaps(dest, src);
       }
-      e.pxor(dest, e.xmm0);
+      e.mov(e.rax, XMMCONSTBASE);
+      e.pxor(dest, XMMCONST(e.rax, XMMOne));
     });
   } else {
     ASSERT_INVALID_TYPE();
@@ -2937,14 +2937,64 @@ table->AddSequence(OPCODE_PERMUTE, [](X64Emitter& e, Instr*& i) {
       }
     } else if (i->src1.value->type == VEC128_TYPE) {
       // Permute bytes between src2 and src3.
-      // TODO(benvanik): check src3 for zero. if 0, we can use pshufb.
-      Xmm dest, control, src2, src3;
-      e.BeginOp(i->dest, dest, REG_DEST,
-                i->src1.value, control, 0,
-                i->src2.value, src2, 0,
-                i->src3.value, src3, 0);
-      UNIMPLEMENTED_SEQ();
-      e.EndOp(dest, control, src2, src3);
+      if (i->src3.value->IsConstantZero()) {
+        // Permuting with src2/zero, so just shuffle/mask.
+        Xmm dest, control, src2;
+        e.BeginOp(i->dest, dest, REG_DEST,
+                  i->src1.value, control, 0,
+                  i->src2.value, src2, 0);
+        if (i->src2.value->IsConstantZero()) {
+          e.vpxor(dest, src2, src2);
+        } else {
+          if (i->src2.value->IsConstant()) {
+            LoadXmmConstant(e, src2, i->src2.value->constant.v128);
+          }
+          // Control mask needs to be shuffled.
+          e.mov(e.rax, XMMCONSTBASE);
+          e.vpshufb(e.xmm0, control, XMMCONST(e.rax, XMMByteSwapMask));
+          e.vpshufb(dest, src2, e.xmm0);
+          // Build a mask with values in src2 having 0 and values in src3 having 1.
+          e.vpcmpgtb(e.xmm0, e.xmm0, XMMCONST(e.rax, XMMPermuteControl15));
+          e.vpandn(dest, e.xmm0, dest);
+        }
+        e.EndOp(dest, control, src2);
+      } else {
+        // General permute.
+        Xmm dest, control, src2, src3;
+        e.BeginOp(i->dest, dest, REG_DEST,
+                  i->src1.value, control, 0,
+                  i->src2.value, src2, 0,
+                  i->src3.value, src3, 0);
+        e.mov(e.rax, XMMCONSTBASE);
+        // Control mask needs to be shuffled.
+        e.vpshufb(e.xmm1, control, XMMCONST(e.rax, XMMByteSwapMask));
+        // Build a mask with values in src2 having 0 and values in src3 having 1.
+        e.vpcmpgtb(dest, e.xmm1, XMMCONST(e.rax, XMMPermuteControl15));
+        Xmm src2_shuf, src3_shuf;
+        if (i->src2.value->IsConstantZero()) {
+          e.vpxor(src2, src2);
+          src2_shuf = src2;
+        } else {
+          if (i->src2.value->IsConstant()) {
+            LoadXmmConstant(e, src2, i->src2.value->constant.v128);
+          }
+          src2_shuf = e.xmm0;
+          e.vpshufb(src2_shuf, src2, e.xmm1);
+        }
+        if (i->src3.value->IsConstantZero()) {
+          e.vpxor(src3, src3);
+          src3_shuf = src3;
+        } else {
+          if (i->src3.value->IsConstant()) {
+            LoadXmmConstant(e, src3, i->src3.value->constant.v128);
+          }
+          // NOTE: reusing xmm1 here.
+          src3_shuf = e.xmm1;
+          e.vpshufb(src3_shuf, src3, e.xmm1);
+        }
+        e.vpblendvb(dest, src2_shuf, src3_shuf, dest);
+        e.EndOp(dest, control, src2, src3);
+      }
     } else {
       ASSERT_INVALID_TYPE();
     }
diff --git a/src/alloy/backend/x64/lowering/op_utils.inl b/src/alloy/backend/x64/lowering/op_utils.inl
index 94aaaef72..3e0ed6789 100644
--- a/src/alloy/backend/x64/lowering/op_utils.inl
+++ b/src/alloy/backend/x64/lowering/op_utils.inl
@@ -52,9 +52,18 @@ Address Stash(X64Emitter& e, const Xmm& r) {
 }
 
 void LoadXmmConstant(X64Emitter& e, Xmm& dest, const vec128_t& v) {
-  e.mov(e.qword[e.rsp + STASH_OFFSET], v.low);
-  e.mov(e.qword[e.rsp + STASH_OFFSET + 8], v.high);
-  e.movaps(dest, e.ptr[e.rsp + STASH_OFFSET]);
+  if (!v.low && !v.high) {
+    // zero
+    e.vpxor(dest, dest);
+  //} else if (v.low == ~0ull && v.high == ~0ull) {
+    // one
+    // TODO(benvanik): XMMCONST?
+  } else {
+    // TODO(benvanik): more efficient loading of partial values?
+    e.mov(e.qword[e.rsp + STASH_OFFSET], v.low);
+    e.mov(e.qword[e.rsp + STASH_OFFSET + 8], v.high);
+    e.vmovaps(dest, e.ptr[e.rsp + STASH_OFFSET]);
+  }
 }
 
 // Moves a 64bit immediate into memory.
@@ -539,8 +548,14 @@ void IntBinaryOpCV(X64Emitter& e, Instr*& i, vv_fn vv_fn, vc_fn vc_fn,
         vv_fn(e, *i, dest, Ntx);
       }
     } else {
-      e.mov(dest, src2);
-      vc_fn(e, *i, dest, (uint32_t)src1->get_constant(CT()));
+      if (i->opcode->flags & OPCODE_FLAG_COMMUNATIVE) {
+        e.mov(dest, src2);
+        vc_fn(e, *i, dest, (uint32_t)src1->get_constant(CT()));
+      } else {
+        // Need a cv_fn. Or a better way to do all of this.
+        e.mov(dest, (uint32_t)src1->get_constant(CT()));
+        vv_fn(e, *i, dest, src2);
+      }
     }
   } else {
     // 64-bit.
diff --git a/src/alloy/backend/x64/x64_emitter.cc b/src/alloy/backend/x64/x64_emitter.cc
index 4d441673f..5aee9fb59 100644
--- a/src/alloy/backend/x64/x64_emitter.cc
+++ b/src/alloy/backend/x64/x64_emitter.cc
@@ -102,21 +102,21 @@ void* X64Emitter::Emplace(size_t stack_size) {
 int X64Emitter::Emit(HIRBuilder* builder) {
   // These are the registers we will not be using. All others are fare game.
   const uint32_t reserved_regs =
-      GetRegBit(rax) |
-      GetRegBit(rcx) |
-      GetRegBit(rdx) |
-      GetRegBit(rsp) |
-      GetRegBit(rbp) |
-      GetRegBit(rsi) |
-      GetRegBit(rdi) |
-      GetRegBit(xmm0) |
+      GetRegBit(rax)  | // scratch
+      GetRegBit(rcx)  | // arg
+      GetRegBit(rdx)  | // arg/clobbered
+      GetRegBit(rsp)  |
+      GetRegBit(rbp)  |
+      GetRegBit(rsi)  |
+      GetRegBit(rdi)  |
+      GetRegBit(r8)   | // arg/clobbered
+      GetRegBit(xmm0) | // scratch
+      GetRegBit(xmm1) | // sometimes used for scratch, could be fixed
 
       // TODO(benvanik): save so that we can use these.
-      GetRegBit(r8) |
-      GetRegBit(r9) |
-      GetRegBit(r10) |
-      GetRegBit(r11) |
-      GetRegBit(xmm1) |
+      GetRegBit(r9)   |
+      GetRegBit(r10)  |
+      GetRegBit(r11)  |
       GetRegBit(xmm2) |
       GetRegBit(xmm3) |
       GetRegBit(xmm4) |