diff --git a/src/init.c b/src/init.c
index 1296eb6..da4ff1e 100644
--- a/src/init.c
+++ b/src/init.c
@@ -653,6 +653,13 @@
   };
 
 #elif XNN_ARCH_PNACL || XNN_ARCH_WASMSIMD
+  // Unlike most other architectures, on x86/x86-64 when floating-point instructions
+  // have no NaN arguments, but produce NaN output, the output NaN has sign bit set.
+  // We use it to distinguish x86/x86-64 from other architectures, by doing subtraction
+  // of two infinities (must produce NaN per IEEE 754 standard).
+  static volatile uint32_t minus_inf = UINT32_C(0xFF800000);
+  const bool is_wasm_x86 = (int32_t) xnn_stub_wasm_f32_sub(minus_inf, minus_inf) < 0;
+
   /**************************** Q8 micro-kernels ****************************/
   xnn_params.q8.gemm = (struct gemm_parameters) {
     .gemm = (xnn_gemm_ukernel_function) xnn_q8_gemm_ukernel_2x2__scalar,
@@ -698,14 +705,27 @@
   };
 
   /**************************** F32 micro-kernels ****************************/
-  xnn_params.f32.gemm = (struct gemm_parameters) {
-    .gemm = (xnn_gemm_ukernel_function) xnn_f32_gemm_ukernel_4x8__psimd_splat,
-    .igemm = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_4x8__psimd_splat,
-    .gemm1 = (xnn_gemm_ukernel_function) xnn_f32_gemm_ukernel_1x8__psimd_loadsplat,
-    .igemm1 = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_1x8__psimd_loadsplat,
-    .mr = 4,
-    .nr = 8,
-  };
+  if (is_wasm_x86) {
+    xnn_params.f32.gemm = (struct gemm_parameters) {
+      .gemm = (xnn_gemm_ukernel_function) xnn_f32_gemm_ukernel_4x8s4__psimd,
+      .igemm = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_4x8s4__psimd,
+      .gemm1 = (xnn_gemm_ukernel_function) xnn_f32_gemm_ukernel_1x8s4__psimd,
+      .igemm1 = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_1x8s4__psimd,
+      .mr = 4,
+      .nr = 8,
+      .log2_sr = 2,
+    };
+  } else {
+    xnn_params.f32.gemm = (struct gemm_parameters) {
+      .gemm = (xnn_gemm_ukernel_function) xnn_f32_gemm_ukernel_6x8s4__psimd,
+      .igemm = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_6x8s4__psimd,
+      .gemm1 = (xnn_gemm_ukernel_function) xnn_f32_igemm_ukernel_1x8s4__psimd,
+      .igemm1 = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_1x8s4__psimd,
+      .mr = 6,
+      .nr = 8,
+      .log2_sr = 2,
+    };
+  }
   xnn_params.f32.gemm2 = (struct gemm_parameters) {
     .gemm = NULL,
     .igemm = (xnn_igemm_ukernel_function) xnn_f32_igemm_ukernel_4x2c4__psimd,