x86/crc32: improve crc32c_arch() code generation with clang

crc32c_arch() is affected by
llvm/llvm-project#20571 where clang
unnecessarily spills the inputs to "rm"-constrained operands to the
stack.  Replace "rm" with ASM_INPUT_RM which partially works around this
by expanding to "r" when the compiler is clang.  This results in better
code generation with clang, though still not optimal.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Eric Biggers <[email protected]>

Author: ebiggers

arch/x86/lib/crc32-glue.c

@@ -55,10 +55,10 @@ u32 crc32c_arch(u32 crc, const u8 *p, size_t len)
 
 	for (num_longs = len / sizeof(unsigned long);
 	     num_longs != 0; num_longs--, p += sizeof(unsigned long))
-		asm(CRC32_INST : "+r" (crc) : "rm" (*(unsigned long *)p));
+		asm(CRC32_INST : "+r" (crc) : ASM_INPUT_RM (*(unsigned long *)p));
 
 	for (len %= sizeof(unsigned long); len; len--, p++)
-		asm("crc32b %1, %0" : "+r" (crc) : "rm" (*p));
+		asm("crc32b %1, %0" : "+r" (crc) : ASM_INPUT_RM (*p));
 
 	return crc;
 }