clang 11 and future GCC are supporting asm goto with outputs.
Use it to implement get_user in order to get better generated code.
Note that clang requires to set x in the default branch of
__get_user_size_goto() otherwise is compliant about x not being
initialised :puzzled:
Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
arch/powerpc/include/asm/uaccess.h | 55 ++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/arch/powerpc/include/asm/uaccess.h
b/arch/powerpc/include/asm/uaccess.h
index e3e53e88cb26..960ab5c04b11 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -136,6 +136,59 @@ do {
\
: "=r" (err) \
: "b" (uaddr), "b" (kaddr), "i" (-EFAULT), "0" (err))
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+
+#define __get_user_asm_goto(x, addr, label, op) \
+ asm_volatile_goto( \
+ "1: "op"%U1%X1 %0, %1 # get_user\n" \
+ EX_TABLE(1b, %l2) \
+ : "=r" (x) \
+ : "m"UPD_CONSTR (*addr) \
+ : \
+ : label)
+
+#ifdef __powerpc64__
+#define __get_user_asm2_goto(x, addr, label) \
+ __get_user_asm_goto(x, addr, label, "ld")
+#else /* __powerpc64__ */
+#define __get_user_asm2_goto(x, addr, label) \
+ asm_volatile_goto( \
+ "1: lwz%X1 %0, %1\n" \
+ "2: lwz%X1 %L0, %L1\n" \
+ EX_TABLE(1b, %l2) \
+ EX_TABLE(2b, %l2) \
+ : "=r" (x) \
+ : "m" (*addr) \
+ : \
+ : label)
+#endif /* __powerpc64__ */
+
+#define __get_user_size_goto(x, ptr, size, label)
\
+do {
\
+ BUILD_BUG_ON(size > sizeof(x));
\
+ switch (size) {
\
+ case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break;
\
+ case 2: __get_user_asm_goto(x, (u16 __user *)ptr, label, "lhz"); break;
\
+ case 4: __get_user_asm_goto(x, (u32 __user *)ptr, label, "lwz"); break;
\
+ case 8: __get_user_asm2_goto(x, (u64 __user *)ptr, label); break;
\
+ default: x = 0; BUILD_BUG();
\
+ }
\
+} while (0)
+
+#define __get_user_size_allowed(x, ptr, size, retval) \
+do { \
+ __label__ __gus_failed; \
+ \
+ __get_user_size_goto(x, ptr, size, __gus_failed); \
+ retval = 0; \
+ break; \
+__gus_failed: \
+ x = 0; \
+ retval = -EFAULT; \
+} while (0)
+
+#else /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
#define __get_user_asm(x, addr, err, op) \
__asm__ __volatile__( \
"1: "op"%U2%X2 %1, %2 # get_user\n" \
@@ -192,6 +245,8 @@ do {
\
goto label; \
} while (0)
+#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
/*
* This is a type: either unsigned long, if the argument fits into
* that type, or otherwise unsigned long long.
--
2.25.0
