Minor cleanup and make padding selection narrower

Author: ntjohnson1

psm/build.rs

@@ -4,7 +4,7 @@ fn find_assembly(
     os: &str,
     env: &str,
     masm: bool,
-    llvm_ar: bool,
+    pad_wasm: bool,
 ) -> Option<(&'static str, bool)> {
     match (arch, endian, os, env) {
         // The implementations for stack switching exist, but, officially, doing so without Fibers
@@ -53,11 +53,12 @@ fn find_assembly(
         ("riscv32", _, _, _) => Some(("src/arch/riscv.s", true)),
         ("riscv64", _, _, _) => Some(("src/arch/riscv64.s", true)),
         ("wasm32", _, _, _) => {
-            if llvm_ar {
+            if pad_wasm {
                 // For wasm32 we ship a precompiled object file.
-                return Some(("src/arch/wasm32.o", true));
+                // Under some conditions we pad the byte count to be divisible by 8
+                Some(("src/arch/wasm32_pad.o", true))
             } else {
-                return Some(("src/arch/wasm32_pad.o", true));
+                Some(("src/arch/wasm32.o", true))
             }
         },
         ("loongarch64", _, _, _) => Some(("src/arch/loongarch64.s", true)),
@@ -93,12 +94,9 @@ fn main() {
     // supports compiling MASM, but that is not stable yet
     let masm = msvc && var("HOST").expect("HOST env not set").contains("windows");
 
-    let llvm_ar = Command::new("llvm-ar")
-        .arg("--version")
-        .output()
-        .is_ok();
+    let pad_wasm = Command::new("clang").arg("--version").output().is_ok() && Command::new("llvm-ar").arg("--version").output().is_err();
 
-    let asm = if let Some((asm, canswitch)) = find_assembly(&arch, &endian, &os, &env, masm, llvm_ar) {
+    let asm = if let Some((asm, canswitch)) = find_assembly(&arch, &endian, &os, &env, masm, pad_wasm) {
         println!("cargo:rustc-cfg=asm");
         println!("cargo:rustc-cfg=link_asm");
         if canswitch {