x86: Use flag output operands for inline asm in atomic-machine.h

Use the flag output constraints feature available in gcc 6+
("=@cc<cond>") instead of explicitly setting a boolean variable
with SETcc instruction.  This approach decouples the instruction
that sets the flags from the code that consumes them, allowing
the compiler to create better code when working with flags users.
Instead of e.g.:

   lock add %esi,(%rdi)
   sets   %sil
   test   %sil,%sil
   jne    <...>

the compiler now generates:

   lock add %esi,(%rdi)
   js     <...>

No functional changes intended.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: H.J.Lu <hjl.tools@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

diff --git a/sysdeps/x86/atomic-machine.h b/sysdeps/x86/atomic-machine.h
index 5452716d2284ab35d109cf4200cc530ac75cf0b7..ac59f77e43075b5676ed4c78a0b57dc5a195c002 100644 (file)
--- a/sysdeps/x86/atomic-machine.h
+++ b/sysdeps/x86/atomic-machine.h
@@ -256,22 +256,22 @@
 
 
 #define atomic_add_negative(mem, value) \
-  ({ unsigned char __result;                                                 \
+  ({ _Bool __result;                                                         \
      if (sizeof (*mem) == 1)                                                 \
-       __asm __volatile (LOCK_PREFIX "addb %b2, %0; sets %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addb %b2, %0"                          \
+                        : "=m" (*mem), "=@ccs" (__result)                    \
                         : IBR_CONSTRAINT (value), "m" (*mem));               \
      else if (sizeof (*mem) == 2)                                            \
-       __asm __volatile (LOCK_PREFIX "addw %w2, %0; sets %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addw %w2, %0"                          \
+                        : "=m" (*mem), "=@ccs" (__result)                    \
                         : "ir" (value), "m" (*mem));                         \
      else if (sizeof (*mem) == 4)                                            \
-       __asm __volatile (LOCK_PREFIX "addl %2, %0; sets %1"                  \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addl %2, %0"                           \
+                        : "=m" (*mem), "=@ccs" (__result)                    \
                         : "ir" (value), "m" (*mem));                         \
      else if (__HAVE_64B_ATOMICS)                                            \
-       __asm __volatile (LOCK_PREFIX "addq %q2, %0; sets %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addq %q2, %0"                          \
+                        : "=m" (*mem), "=@ccs" (__result)                    \
                         : "ir" ((int64_t) cast_to_integer (value)),          \
                           "m" (*mem));                                       \
      else                                                                    \
@@ -280,26 +280,26 @@
 
 
 #define atomic_add_zero(mem, value) \
-  ({ unsigned char __result;                                                 \
+  ({ _Bool __result;                                                         \
      if (sizeof (*mem) == 1)                                                 \
-       __asm __volatile (LOCK_PREFIX "addb %b2, %0; setz %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addb %b2, %0"                          \
+                        : "=m" (*mem), "=@ccz" (__result)                    \
                         : IBR_CONSTRAINT (value), "m" (*mem));               \
      else if (sizeof (*mem) == 2)                                            \
-       __asm __volatile (LOCK_PREFIX "addw %w2, %0; setz %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addw %w2, %0"                          \
+                        : "=m" (*mem), "=@ccz" (__result)                    \
                         : "ir" (value), "m" (*mem));                         \
      else if (sizeof (*mem) == 4)                                            \
-       __asm __volatile (LOCK_PREFIX "addl %2, %0; setz %1"                  \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addl %2, %0"                           \
+                        : "=m" (*mem), "=@ccz" (__result)                    \
                         : "ir" (value), "m" (*mem));                         \
      else if (__HAVE_64B_ATOMICS)                                            \
-       __asm __volatile (LOCK_PREFIX "addq %q2, %0; setz %1"                 \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "addq %q2, %0"                          \
+                        : "=m" (*mem), "=@ccz" (__result)                    \
                         : "ir" ((int64_t) cast_to_integer (value)),          \
                           "m" (*mem));                                       \
      else                                                                    \
-       __atomic_link_error ();                                       \
+       __atomic_link_error ();                                               \
      __result; })
 
 
@@ -339,25 +339,25 @@
 
 
 #define atomic_increment_and_test(mem) \
-  ({ unsigned char __result;                                                 \
+  ({ _Bool __result;                                                         \
      if (sizeof (*mem) == 1)                                                 \
-       __asm __volatile (LOCK_PREFIX "incb %b0; sete %b1"                    \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "incb %b0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else if (sizeof (*mem) == 2)                                            \
-       __asm __volatile (LOCK_PREFIX "incw %w0; sete %w1"                    \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "incw %w0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else if (sizeof (*mem) == 4)                                            \
-       __asm __volatile (LOCK_PREFIX "incl %0; sete %1"                              \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "incl %0"                               \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else if (__HAVE_64B_ATOMICS)                                            \
-       __asm __volatile (LOCK_PREFIX "incq %q0; sete %1"                     \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "incq %q0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else                                                                    \
-       __atomic_link_error ();                                       \
+       __atomic_link_error ();                                               \
      __result; })
 
 
@@ -397,22 +397,22 @@
 
 
 #define atomic_decrement_and_test(mem) \
-  ({ unsigned char __result;                                                 \
+  ({ _Bool __result;                                                         \
      if (sizeof (*mem) == 1)                                                 \
-       __asm __volatile (LOCK_PREFIX "decb %b0; sete %1"                     \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "decb %b0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else if (sizeof (*mem) == 2)                                            \
-       __asm __volatile (LOCK_PREFIX "decw %w0; sete %1"                     \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "decw %w0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else if (sizeof (*mem) == 4)                                            \
-       __asm __volatile (LOCK_PREFIX "decl %0; sete %1"                              \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "decl %0"                               \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      else                                                                    \
-       __asm __volatile (LOCK_PREFIX "decq %q0; sete %1"                     \
-                        : "=m" (*mem), "=qm" (__result)                      \
+       __asm __volatile (LOCK_PREFIX "decq %q0"                                      \
+                        : "=m" (*mem), "=@cce" (__result)                    \
                         : "m" (*mem));                                       \
      __result; })
 
@@ -445,25 +445,25 @@
 
 
 #define atomic_bit_test_set(mem, bit) \
-  ({ unsigned char __result;                                                 \
+  ({ _Bool __result;                                                         \
      if (sizeof (*mem) == 1)                                                 \
-       __asm __volatile (LOCK_PREFIX "btsb %3, %1; setc %0"                  \
-                        : "=q" (__result), "=m" (*mem)                       \
+       __asm __volatile (LOCK_PREFIX "btsb %3, %1"                           \
+                        : "=@ccc" (__result), "=m" (*mem)                    \
                         : "m" (*mem), IBR_CONSTRAINT (bit));                 \
      else if (sizeof (*mem) == 2)                                            \
-       __asm __volatile (LOCK_PREFIX "btsw %3, %1; setc %0"                  \
-                        : "=q" (__result), "=m" (*mem)                       \
+       __asm __volatile (LOCK_PREFIX "btsw %3, %1"                           \
+                        : "=@ccc" (__result), "=m" (*mem)                    \
                         : "m" (*mem), "ir" (bit));                           \
      else if (sizeof (*mem) == 4)                                            \
-       __asm __volatile (LOCK_PREFIX "btsl %3, %1; setc %0"                  \
-                        : "=q" (__result), "=m" (*mem)                       \
+       __asm __volatile (LOCK_PREFIX "btsl %3, %1"                           \
+                        : "=@ccc" (__result), "=m" (*mem)                    \
                         : "m" (*mem), "ir" (bit));                           \
      else if (__HAVE_64B_ATOMICS)                                            \
-       __asm __volatile (LOCK_PREFIX "btsq %3, %1; setc %0"                  \
-                        : "=q" (__result), "=m" (*mem)                       \
+       __asm __volatile (LOCK_PREFIX "btsq %3, %1"                           \
+                        : "=@ccc" (__result), "=m" (*mem)                    \
                         : "m" (*mem), "ir" (bit));                           \
      else                                                                    \
-       __atomic_link_error ();                                       \
+       __atomic_link_error ();                                               \
      __result; })