diff --git a/src/alloy/backend/x64/x64_emitter.cc b/src/alloy/backend/x64/x64_emitter.cc
index 684fcaa86..3ee6ab59c 100644
--- a/src/alloy/backend/x64/x64_emitter.cc
+++ b/src/alloy/backend/x64/x64_emitter.cc
@@ -431,8 +431,8 @@ Address X64Emitter::GetXmmConstPtr(XmmConst id) {
     /* XMMZero                */ vec128f(0.0f, 0.0f, 0.0f, 0.0f),
     /* XMMOne                 */ vec128f(1.0f, 1.0f, 1.0f, 1.0f),
     /* XMMNegativeOne         */ vec128f(-1.0f, -1.0f, -1.0f, -1.0f),
-    /* XMMMaskX16Y16          */ vec128i(0x0000FFFF, 0xFFFF0000, 0x00000000, 0x00000000),
-    /* XMMFlipX16Y16          */ vec128i(0x00008000, 0x00000000, 0x00000000, 0x00000000),
+    /* XMMMaskX16Y16          */ vec128i(0x0000FFFFu, 0xFFFF0000u, 0x00000000u, 0x00000000u),
+    /* XMMFlipX16Y16          */ vec128i(0x00008000u, 0x00000000u, 0x00000000u, 0x00000000u),
     /* XMMFixX16Y16           */ vec128f(-32768.0f, 0.0f, 0.0f, 0.0f),
     /* XMMNormalizeX16Y16     */ vec128f(1.0f / 32767.0f, 1.0f / (32767.0f * 65536.0f), 0.0f, 0.0f),
     /* XMM3301                */ vec128f(3.0f, 3.0f, 0.0f, 1.0f),
@@ -440,11 +440,13 @@ Address X64Emitter::GetXmmConstPtr(XmmConst id) {
     /* XMMSignMaskPD          */ vec128i(0x00000000u, 0x80000000u, 0x00000000u, 0x80000000u),
     /* XMMByteSwapMask        */ vec128i(0x00010203u, 0x04050607u, 0x08090A0Bu, 0x0C0D0E0Fu),
     /* XMMPermuteControl15    */ vec128b(15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15),
-    /* XMMUnpackD3DCOLOR      */ vec128i(0xFFFFFF02, 0xFFFFFF01, 0xFFFFFF00, 0xFFFFFF02),
+    /* XMMPackD3DCOLOR        */ vec128i(0xFFFFFFFFu, 0xFFFFFFFFu, 0xFFFFFFFFu, 0x0C000408u),
+    /* XMMUnpackD3DCOLOR      */ vec128i(0xFFFFFF02u, 0xFFFFFF01u, 0xFFFFFF00u, 0xFFFFFF03u),
     /* XMMOneOver255          */ vec128f(1.0f / 255.0f, 1.0f / 255.0f, 1.0f / 255.0f, 1.0f / 255.0f),
     /* XMMShiftMaskPS         */ vec128i(0x0000001Fu, 0x0000001Fu, 0x0000001Fu, 0x0000001Fu),
     /* XMMShiftByteMask       */ vec128i(0x000000FFu, 0x000000FFu, 0x000000FFu, 0x000000FFu),
     /* XMMUnsignedDwordMax    */ vec128i(0xFFFFFFFFu, 0x00000000u, 0xFFFFFFFFu, 0x00000000u),
+    /* XMM255                 */ vec128f(255.0f, 255.0f, 255.0f, 255.0f),
   };
   // TODO(benvanik): cache base pointer somewhere? stack? It'd be nice to
   // prevent this move.
diff --git a/src/alloy/backend/x64/x64_emitter.h b/src/alloy/backend/x64/x64_emitter.h
index 3ac92be3f..4b05e5134 100644
--- a/src/alloy/backend/x64/x64_emitter.h
+++ b/src/alloy/backend/x64/x64_emitter.h
@@ -48,11 +48,13 @@ enum XmmConst {
   XMMSignMaskPD         = 9,
   XMMByteSwapMask       = 10,
   XMMPermuteControl15   = 11,
-  XMMUnpackD3DCOLOR     = 12,
-  XMMOneOver255         = 13,
-  XMMShiftMaskPS        = 14,
-  XMMShiftByteMask      = 15,
-  XMMUnsignedDwordMax   = 16,
+  XMMPackD3DCOLOR       = 12,
+  XMMUnpackD3DCOLOR     = 13,
+  XMMOneOver255         = 14,
+  XMMShiftMaskPS        = 15,
+  XMMShiftByteMask      = 16,
+  XMMUnsignedDwordMax   = 17,
+  XMM255                = 18,
 };
 
 // Unfortunately due to the design of xbyak we have to pass this to the ctor.
diff --git a/src/alloy/backend/x64/x64_sequences.cc b/src/alloy/backend/x64/x64_sequences.cc
index d60404aa1..3c5da0755 100644
--- a/src/alloy/backend/x64/x64_sequences.cc
+++ b/src/alloy/backend/x64/x64_sequences.cc
@@ -4582,7 +4582,27 @@ EMITTER(PACK, MATCH(I<OPCODE_PACK, V128<>, V128<>>)) {
     }
   }
   static void EmitD3DCOLOR(X64Emitter& e, const EmitArgType& i) {
-    XEASSERTALWAYS();
+    // RGBA (XYZW) -> ARGB (WXYZ)
+    // float r = roundf(((src1.x < 0) ? 0 : ((1 < src1.x) ? 1 : src1.x)) * 255);
+    // float g = roundf(((src1.y < 0) ? 0 : ((1 < src1.y) ? 1 : src1.y)) * 255);
+    // float b = roundf(((src1.z < 0) ? 0 : ((1 < src1.z) ? 1 : src1.z)) * 255);
+    // float a = roundf(((src1.w < 0) ? 0 : ((1 < src1.w) ? 1 : src1.w)) * 255);
+    // dest.iw = ((uint32_t)a << 24) |
+    //           ((uint32_t)r << 16) |
+    //           ((uint32_t)g << 8) |
+    //           ((uint32_t)b);
+    // f2i(clamp(src, 0, 1) * 255)
+    e.vpxor(e.xmm0, e.xmm0);
+    if (i.src1.is_constant) {
+      e.LoadConstantXmm(e.xmm1, i.src1.constant());
+      e.vmaxps(e.xmm0, e.xmm1);
+    } else {
+      e.vmaxps(e.xmm0, i.src1);
+    }
+    e.vminps(e.xmm0, e.GetXmmConstPtr(XMMOne));
+    e.vmulps(e.xmm0, e.GetXmmConstPtr(XMM255));
+    e.vcvttps2dq(e.xmm0, e.xmm0);
+    e.vpshufb(i.dest, e.xmm0, e.GetXmmConstPtr(XMMPackD3DCOLOR));
   }
   static void EmitFLOAT16_2(X64Emitter& e, const EmitArgType& i) {
     XEASSERTALWAYS();