Take #593 into account.

Author: ncruces

libc-top-half/musl/src/string/memchr.c

@@ -15,24 +15,34 @@
 void *memchr(const void *src, int c, size_t n)
 {
 #if defined(__wasm_simd128__) && defined(__wasilibc_simd_string)
+	// Skip Clang 19 and Clang 20 which have a bug (llvm/llvm-project#146574)
+	// which results in an ICE when inline assembly is used with a vector result.
+#if __clang_major__ != 19 && __clang_major__ != 20
 	// When n is zero, a function that locates a character finds no occurrence.
 	// Otherwise, decrement n to ensure sub_overflow overflows
 	// when n would go equal-to-or-below zero.
 	if (!n--) {
 		return NULL;
 	}
 
-	// memchr must behave as if it reads characters sequentially
-	// and stops as soon as a match is found.
-	// Aligning ensures loads beyond the first match are safe.
-	// Casting through uintptr_t makes this implementation-defined,
-	// rather than undefined behavior.
+	// Note that reading before/after the allocation of a pointer is UB in
+	// C, so inline assembly is used to generate the exact machine
+	// instruction we want with opaque semantics to the compiler to avoid
+	// the UB.
 	uintptr_t align = (uintptr_t)src % sizeof(v128_t);
-	const v128_t *v = (v128_t *)((uintptr_t)src - align);
-	const v128_t vc = wasm_i8x16_splat(c);
+	uintptr_t addr = (uintptr_t)src - align;
+	v128_t vc = wasm_i8x16_splat(c);
 
 	for (;;) {
-		const v128_t cmp = wasm_i8x16_eq(*v, vc);
+		v128_t v;
+		__asm__ (
+			"local.get %1\n"
+			"v128.load 0\n"
+			"local.set %0\n"
+			: "=r"(v)
+			: "r"(addr)
+			: "memory");
+		v128_t cmp = wasm_i8x16_eq(v, vc);
 		// Bitmask is slow on AArch64, any_true is much faster.
 		if (wasm_v128_any_true(cmp)) {
 			// Clear the bits corresponding to align (little-endian)
@@ -48,16 +58,18 @@ void *memchr(const void *src, int c, size_t n)
 				// That's a match, unless it is beyond the end of the object.
 				// Recall that we decremented n, so less-than-or-equal-to is correct.
 				size_t ctz = __builtin_ctz(mask);
-				return ctz - align <= n ? (char *)v + ctz : NULL;
+				return ctz - align <= n ? (char *)src + (addr + ctz - (uintptr_t)src)
+				                        : NULL;
 			}
 		}
 		// Decrement n; if it overflows we're done.
 		if (__builtin_sub_overflow(n, sizeof(v128_t) - align, &n)) {
 			return NULL;
 		}
 		align = 0;
-		v++;
+		addr += sizeof(v128_t);
 	}
+#endif
 #endif
 
 	const unsigned char *s = src;

libc-top-half/musl/src/string/strlen.c

@@ -14,28 +14,28 @@
 size_t strlen(const char *s)
 {
 #if defined(__wasm_simd128__) && defined(__wasilibc_simd_string)
-// Skip Clang 19 and Clang 20 which have a bug (llvm/llvm-project#146574) which
-// results in an ICE when inline assembly is used with a vector result.
+	// Skip Clang 19 and Clang 20 which have a bug (llvm/llvm-project#146574)
+	// which results in an ICE when inline assembly is used with a vector result.
 #if __clang_major__ != 19 && __clang_major__ != 20
-        // Note that reading before/after the allocation of a pointer is UB in
-        // C, so inline assembly is used to generate the exact machine
-        // instruction we want with opaque semantics to the compiler to avoid
-        // the UB.
+	// Note that reading before/after the allocation of a pointer is UB in
+	// C, so inline assembly is used to generate the exact machine
+	// instruction we want with opaque semantics to the compiler to avoid
+	// the UB.
 	uintptr_t align = (uintptr_t)s % sizeof(v128_t);
-	uintptr_t v = (uintptr_t)s - align;
+	uintptr_t addr = (uintptr_t)s - align;
 
 	for (;;) {
-                v128_t chunk;
+		v128_t v;
 		__asm__ (
 			"local.get %1\n"
 			"v128.load 0\n"
 			"local.set %0\n"
-			: "=r"(chunk)
-                        : "r"(v)
-                        : "memory");
+			: "=r"(v)
+			: "r"(addr)
+			: "memory");
 		// Bitmask is slow on AArch64, all_true is much faster.
-		if (!wasm_i8x16_all_true(chunk)) {
-			const v128_t cmp = wasm_i8x16_eq(chunk, (v128_t){});
+		if (!wasm_i8x16_all_true(v)) {
+			const v128_t cmp = wasm_i8x16_eq(v, (v128_t){});
 			// Clear the bits corresponding to align (little-endian)
 			// so we can count trailing zeros.
 			int mask = wasm_i8x16_bitmask(cmp) >> align << align;
@@ -46,11 +46,11 @@ size_t strlen(const char *s)
 			// it's as if we didn't find anything.
 			if (mask) {
 				// Find the offset of the first one bit (little-endian).
-				return v - (uintptr_t)s + __builtin_ctz(mask);
+				return addr - (uintptr_t)s + __builtin_ctz(mask);
 			}
 		}
 		align = 0;
-		v += sizeof(v128_t);
+		addr += sizeof(v128_t);
 	}
 #endif
 #endif