[PATCH,AIX] Enable Stack Unwinding on AIX

["REIX, Tony" <tony.reix@atos.net>]

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Description:
 * This patch enables the stack unwinding on AIX.

Tests:
 * Fedora25/x86_64 + GCC v7.1.0 : Configure/Build: SUCCESS
   - build made by means of a .spec file based on Fedora gcc-7.0.1-0.12 .spec file
     ../configure --enable-bootstrap --enable-languages=c,c++,objc,obj-c++,fortran,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl --enable-libmpx --enable-offload-targets=nvptx-none --without-cuda-driver --enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux

ChangeLog:
  * libgcc/config/rs6000/aix-unwind.h : Implements stack unwinding on AIX.

Regards,

Tony Reix
Bull - ATOS
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net

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--- ./libgcc/config/rs6000/aix-unwind.h	2017-01-02 01:20:05 -0600
+++ ./libgcc/config/rs6000/aix-unwind.h	2017-04-28 10:03:16 -0500
@@ -64,7 +64,8 @@
 #endif
 
 /* Now on to MD_FALLBACK_FRAME_STATE_FOR.
-   32bit AIX 5.2, 5.3 and 7.1 only at this stage.  */
+   32bit AIX 5.2, 5.3, 6.1, 7.X and
+   64bit AIX 6.1, 7.X only at this stage.  */
 
 #include <stdlib.h>
 #include <stddef.h>
@@ -73,10 +74,10 @@
 
 #ifdef __64BIT__
 
-/* 64bit fallback not implemented yet, so MD_FALLBACK_FRAME_STATE_FOR not
-   defined.  Arrange just for the code below to compile.  */
 typedef struct __context64 mstate_t;
 
+#define MD_FALLBACK_FRAME_STATE_FOR ppc_aix_fallback_frame_state
+
 #else
 
 typedef struct mstsave mstate_t;
@@ -128,10 +129,26 @@ ucontext_for (struct _Unwind_Context *co
 {
   const unsigned int * ra = context->ra;
 
-  /* AIX 5.2, 5.3 and 7.1, threaded or not, share common patterns
+  /* AIX 5.2, 5.3, 6.1 and 7.X, threaded or not, share common patterns
      and feature variants depending on the configured kernel (unix_mp
      or unix_64).  */
 
+#ifdef __64BIT__
+  if (*(ra - 5) == 0x4c00012c     /* isync             */
+      && *(ra - 4) == 0xe8ec0000  /* ld      r7,0(r12) */
+      && *(ra - 3) == 0xe84c0008  /* ld      r2,8(r12) */
+      && *(ra - 2) == 0x7ce903a6  /* mtctr   r7        */
+      && *(ra - 1) == 0x4e800421  /* bctrl             */
+      && *(ra - 0) == 0x7de27b78) /* mr      r2,r15   <-- context->ra */
+    {
+      /* unix_64 */
+      if (*(ra - 6) == 0x7d000164)  /* mtmsrd  r8 */
+        {
+          /* AIX 6.1, 7.1 and 7.2 */
+          return (ucontext_t *)(context->cfa + 0x70);
+        }
+    }
+#else
   if (*(ra - 5) == 0x4c00012c     /* isync             */
       && *(ra - 4) == 0x80ec0000  /* lwz     r7,0(r12) */
       && *(ra - 3) == 0x804c0004  /* lwz     r2,4(r12) */
@@ -152,10 +169,14 @@ ucontext_for (struct _Unwind_Context *co
 	    case 0x835a0570:  /* lwz r26,1392(r26) */
 	      return (ucontext_t *)(context->cfa + 0x40);
 
-	      /* AIX 7.1 */
+	      /* AIX 6.1 and 7.1 */
 	    case 0x2c1a0000:  /* cmpwi   r26,0 */
 	      return (ucontext_t *)(context->cfa + 0x40);
-		
+
+	      /* AIX 7.2 */
+	    case 0x3800000a:  /* li   r0,A */
+	      return (ucontext_t *)(context->cfa + 0x40);
+
 	    default:
 	      return 0;
 	    }
@@ -174,7 +195,7 @@ ucontext_for (struct _Unwind_Context *co
 	  return &frame->ucontext;
 	}
     }
-
+#endif
   return 0;
 }