Changeset a35a3d8 in mainline for uspace/lib/c/arch/ia64/src/fibril.S

Timestamp:

2018-03-12T17:13:46Z (7 years ago)

Author:

GitHub <noreply@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

b127e4af

Parents:

f3d47c97

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2018-03-12 17:13:46)

git-committer:

GitHub <noreply@…> (2018-03-12 17:13:46)

Message:

Turn context_save/context_restore into standard setjmp/longjmp. (#24)

Turn context_save()/context_restore() into semi-standard __setjmp()/__longjmp().

The original context_* functions are similar to setjmp()/longjmp(), except that the return value is more restricted for the former, and with inverted meaning. This commit adopts the standard return value semantics and acknowledges that these functions are "standard setjmp()/longjmp() with additional implementation-specific properties" by changing the name. The only divergence from the standard is that __longjmp() causes __setjmp() to return its value unchanged, even if it is zero. This is just to avoid extra assembly, and longjmp() checks this in C.

Note that the original use of context_save()/context_restore() to implement context switching in fibril implementation has already been delegated to context_create()/context_swap(), which provide more natural control flow.

File:

• uspace/lib/c/arch/ia64/src/fibril.S (modified) (4 diffs)

uspace/lib/c/arch/ia64/src/fibril.S

@@ -32 +32 @@
 .text
 
-FUNCTION_BEGIN(context_save)
+FUNCTION_BEGIN(__setjmp)
         alloc loc0 = ar.pfs, 1, 49, 0, 0
         mov loc1 = ar.unat ;;
@@ -178 +178 @@
         mov ar.unat = loc1
 
-        add r8 = r0, r0, 1      /* context_save returns 1 */
+        mov r8 = 0      /* __setjmp returns 0 */
         br.ret.sptk.many b0
-FUNCTION_END(context_save)
-
-FUNCTION_BEGIN(context_restore)
-        alloc loc0 = ar.pfs, 1, 50, 0, 0        ;;
+FUNCTION_END(__setjmp)
+
+FUNCTION_BEGIN(__longjmp)
+        alloc loc0 = ar.pfs, 2, 51, 0, 0        ;;
 
         add loc9 = CONTEXT_OFFSET_AR_PFS, in0
@@ -230 +230 @@
         add loc47 = CONTEXT_OFFSET_F29, in0
         add loc48 = CONTEXT_OFFSET_F30, in0
-        add loc49 = CONTEXT_OFFSET_F31, in0 ;;
+        add loc49 = CONTEXT_OFFSET_F31, in0
+        mov loc50 = in1 ;;
 
         ld8 loc0 = [loc9]       /* load ar.pfs */
@@ -335 +336 @@
         mov ar.unat = loc1
 
-        mov r8 = r0                     /* context_restore returns 0 */
+        mov r8 = loc50                  /* __longjmp returns second argument */
         br.ret.sptk.many b0
-FUNCTION_END(context_restore)
+FUNCTION_END(__longjmp)