d: Merge upstream dmd 934df6f8c, druntime 7bdd83d7

Corrects a previous change made to the SPARC stdc bindings, and
backports PPC-related fixes.  The library and language testsuite now
passes fully on powerpc64le-linux-gnu.

Fixes: PR d/90719
Fixes: PR d/94825

Reviewed-on: https://github.com/dlang/dmd/pull/11079
	     https://github.com/dlang/druntime/pull/3078
	     https://github.com/dlang/druntime/pull/3083

libphobos/ChangeLog:

	PR d/94825
	* libdruntime/Makefile.am (DRUNTIME_SOURCES_CONFIGURED): Remove
	config/powerpc/switchcontext.S
	* libdruntime/Makefile.in: Regenerate.
	* libdruntime/config/powerpc/callwithstack.S: Remove.
	* libdruntime/config/powerpc/switchcontext.S: Fix symbol name of
	fiber_switchContext.
	* libdruntime/core/thread.d: Disable fiber migration tests on PPC.
	* testsuite/libphobos.thread/fiber_guard_page.d: Set guardPageSize
	same as stackSize.

9 files changed, 96 insertions, 269 deletions

diff --git a/libphobos/libdruntime/MERGE b/libphobos/libdruntime/MERGE
index c6357317ddc..c61ad7ca7ed 100644
--- a/libphobos/libdruntime/MERGE
+++ b/libphobos/libdruntime/MERGE
@@ -1,4 +1,4 @@
-476882795473a884f837bea6da850ac5181868d1
+7bdd83d7b4bd9fd4cb9ffca0d50babc90b31bfd6
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/druntime repository.
diff --git a/libphobos/libdruntime/Makefile.am b/libphobos/libdruntime/Makefile.am
index e1dc24c660b..1d340a0041c 100644
--- a/libphobos/libdruntime/Makefile.am
+++ b/libphobos/libdruntime/Makefile.am
@@ -81,8 +81,7 @@ if DRUNTIME_CPU_MIPS
     DRUNTIME_SOURCES_CONFIGURED += config/mips/switchcontext.S
 endif
 if DRUNTIME_CPU_POWERPC
-    DRUNTIME_SOURCES_CONFIGURED += config/powerpc/callwithstack.S \
-				   config/powerpc/switchcontext.S
+    DRUNTIME_SOURCES_CONFIGURED += config/powerpc/switchcontext.S
 endif
 if DRUNTIME_CPU_X86
 if DRUNTIME_OS_MINGW
diff --git a/libphobos/libdruntime/Makefile.in b/libphobos/libdruntime/Makefile.in
index 694de3e0b43..3fddbc340de 100644
--- a/libphobos/libdruntime/Makefile.in
+++ b/libphobos/libdruntime/Makefile.in
@@ -123,9 +123,7 @@ target_triplet = @target@
 @DRUNTIME_CPU_AARCH64_TRUE@am__append_11 = config/aarch64/switchcontext.S
 @DRUNTIME_CPU_ARM_TRUE@am__append_12 = config/arm/switchcontext.S
 @DRUNTIME_CPU_MIPS_TRUE@am__append_13 = config/mips/switchcontext.S
-@DRUNTIME_CPU_POWERPC_TRUE@am__append_14 = config/powerpc/callwithstack.S \
-@DRUNTIME_CPU_POWERPC_TRUE@				   config/powerpc/switchcontext.S
-
+@DRUNTIME_CPU_POWERPC_TRUE@am__append_14 = config/powerpc/switchcontext.S
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_TRUE@am__append_15 = config/mingw/switchcontext.S
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_FALSE@am__append_16 = config/x86/switchcontext.S
 @DRUNTIME_CPU_SYSTEMZ_TRUE@am__append_17 = config/systemz/get_tls_offset.S
@@ -441,8 +439,7 @@ am__objects_21 = core/sys/solaris/dlfcn.lo core/sys/solaris/elf.lo \
 @DRUNTIME_CPU_AARCH64_TRUE@am__objects_23 = config/aarch64/libgdruntime_la-switchcontext.lo
 @DRUNTIME_CPU_ARM_TRUE@am__objects_24 = config/arm/libgdruntime_la-switchcontext.lo
 @DRUNTIME_CPU_MIPS_TRUE@am__objects_25 = config/mips/libgdruntime_la-switchcontext.lo
-@DRUNTIME_CPU_POWERPC_TRUE@am__objects_26 = config/powerpc/libgdruntime_la-callwithstack.lo \
-@DRUNTIME_CPU_POWERPC_TRUE@	config/powerpc/libgdruntime_la-switchcontext.lo
+@DRUNTIME_CPU_POWERPC_TRUE@am__objects_26 = config/powerpc/libgdruntime_la-switchcontext.lo
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_TRUE@am__objects_27 = config/mingw/libgdruntime_la-switchcontext.lo
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_FALSE@am__objects_28 = config/x86/libgdruntime_la-switchcontext.lo
 @DRUNTIME_CPU_SYSTEMZ_TRUE@am__objects_29 = config/systemz/libgdruntime_la-get_tls_offset.lo
@@ -463,8 +460,7 @@ am__objects_34 = core/stdc/libgdruntime_convenience_la-errno_.lo
 @DRUNTIME_CPU_AARCH64_TRUE@am__objects_35 = config/aarch64/libgdruntime_convenience_la-switchcontext.lo
 @DRUNTIME_CPU_ARM_TRUE@am__objects_36 = config/arm/libgdruntime_convenience_la-switchcontext.lo
 @DRUNTIME_CPU_MIPS_TRUE@am__objects_37 = config/mips/libgdruntime_convenience_la-switchcontext.lo
-@DRUNTIME_CPU_POWERPC_TRUE@am__objects_38 = config/powerpc/libgdruntime_convenience_la-callwithstack.lo \
-@DRUNTIME_CPU_POWERPC_TRUE@	config/powerpc/libgdruntime_convenience_la-switchcontext.lo
+@DRUNTIME_CPU_POWERPC_TRUE@am__objects_38 = config/powerpc/libgdruntime_convenience_la-switchcontext.lo
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_TRUE@am__objects_39 = config/mingw/libgdruntime_convenience_la-switchcontext.lo
 @DRUNTIME_CPU_X86_TRUE@@DRUNTIME_OS_MINGW_FALSE@am__objects_40 = config/x86/libgdruntime_convenience_la-switchcontext.lo
 @DRUNTIME_CPU_SYSTEMZ_TRUE@am__objects_41 = config/systemz/libgdruntime_convenience_la-get_tls_offset.lo
@@ -1748,8 +1744,6 @@ config/mips/libgdruntime_la-switchcontext.lo:  \
 config/powerpc/$(am__dirstamp):
 	@$(MKDIR_P) config/powerpc
 	@: > config/powerpc/$(am__dirstamp)
-config/powerpc/libgdruntime_la-callwithstack.lo:  \
-	config/powerpc/$(am__dirstamp)
 config/powerpc/libgdruntime_la-switchcontext.lo:  \
 	config/powerpc/$(am__dirstamp)
 config/mingw/$(am__dirstamp):
@@ -1785,8 +1779,6 @@ config/arm/libgdruntime_convenience_la-switchcontext.lo:  \
 	config/arm/$(am__dirstamp)
 config/mips/libgdruntime_convenience_la-switchcontext.lo:  \
 	config/mips/$(am__dirstamp)
-config/powerpc/libgdruntime_convenience_la-callwithstack.lo:  \
-	config/powerpc/$(am__dirstamp)
 config/powerpc/libgdruntime_convenience_la-switchcontext.lo:  \
 	config/powerpc/$(am__dirstamp)
 config/mingw/libgdruntime_convenience_la-switchcontext.lo:  \
@@ -1921,9 +1913,6 @@ config/arm/libgdruntime_la-switchcontext.lo: config/arm/switchcontext.S
 config/mips/libgdruntime_la-switchcontext.lo: config/mips/switchcontext.S
 	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/mips/libgdruntime_la-switchcontext.lo `test -f 'config/mips/switchcontext.S' || echo '$(srcdir)/'`config/mips/switchcontext.S
 
-config/powerpc/libgdruntime_la-callwithstack.lo: config/powerpc/callwithstack.S
-	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/powerpc/libgdruntime_la-callwithstack.lo `test -f 'config/powerpc/callwithstack.S' || echo '$(srcdir)/'`config/powerpc/callwithstack.S
-
 config/powerpc/libgdruntime_la-switchcontext.lo: config/powerpc/switchcontext.S
 	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/powerpc/libgdruntime_la-switchcontext.lo `test -f 'config/powerpc/switchcontext.S' || echo '$(srcdir)/'`config/powerpc/switchcontext.S
 
@@ -1948,9 +1937,6 @@ config/arm/libgdruntime_convenience_la-switchcontext.lo: config/arm/switchcontex
 config/mips/libgdruntime_convenience_la-switchcontext.lo: config/mips/switchcontext.S
 	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_convenience_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/mips/libgdruntime_convenience_la-switchcontext.lo `test -f 'config/mips/switchcontext.S' || echo '$(srcdir)/'`config/mips/switchcontext.S
 
-config/powerpc/libgdruntime_convenience_la-callwithstack.lo: config/powerpc/callwithstack.S
-	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_convenience_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/powerpc/libgdruntime_convenience_la-callwithstack.lo `test -f 'config/powerpc/callwithstack.S' || echo '$(srcdir)/'`config/powerpc/callwithstack.S
-
 config/powerpc/libgdruntime_convenience_la-switchcontext.lo: config/powerpc/switchcontext.S
 	$(AM_V_CPPAS)$(LIBTOOL) $(AM_V_lt) $(libgdruntime_convenience_la_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CCAS) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CCASFLAGS) $(CCASFLAGS) -c -o config/powerpc/libgdruntime_convenience_la-switchcontext.lo `test -f 'config/powerpc/switchcontext.S' || echo '$(srcdir)/'`config/powerpc/switchcontext.S
 
diff --git a/libphobos/libdruntime/config/powerpc/callwithstack.S b/libphobos/libdruntime/config/powerpc/callwithstack.S
deleted file mode 100644
index 0752c5d0322..00000000000
--- a/libphobos/libdruntime/config/powerpc/callwithstack.S
+++ /dev/null
@@ -1,172 +0,0 @@
-/* PowerPC64 support code for fibers and multithreading.
-   Copyright (C) 2019-2020 Free Software Foundation, Inc.
-
-This file is part of GCC.
-
-GCC is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free
-Software Foundation; either version 3, or (at your option) any later
-version.
-
-GCC is distributed in the hope that it will be useful, but WITHOUT ANY
-WARRANTY; without even the implied warranty of MERCHANTABILITY or
-FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-for more details.
-
-Under Section 7 of GPL version 3, you are granted additional
-permissions described in the GCC Runtime Library Exception, version
-3.1, as published by the Free Software Foundation.
-
-You should have received a copy of the GNU General Public License and
-a copy of the GCC Runtime Library Exception along with this program;
-see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
-<http://www.gnu.org/licenses/>.  */
-
-#include "../common/threadasm.S"
-
-#if defined(__PPC64__)
-
-#if defined(_CALL_ELF) && _CALL_ELF == 2
-#define USE_ABI_2
-#define LINKAGE_SZ   32
-#define LR_OFS       16
-#define TOC_OFS      24
-#define GPR_OFS      32
-#define STACK_SZ     (LINKAGE_SZ + 26*8)
-#define OFS_R3_R10   GPR_OFS
-#define OFS_R14_R31  (GPR_OFS+8*8)
-#else
-#define LINKAGE_SZ   48
-#define LR_OFS       16
-#define TOC_OFS      40
-#define GPR_OFS      112
-#define STACK_SZ     (LINKAGE_SZ + 8*8 + 18*8)
-#define OFS_R3_R10   (STACK_SZ+LINKAGE_SZ)
-#define OFS_R14_R31  GPR_OFS
-#endif
-
-    .text
-#if defined( USE_ABI_2 )
-    .abiversion 2
-#endif
-    .globl  _D4core6thread18callWithStackShellFNbMDFNbPvZvZv
-    .align  2
-    .type   _D4core6thread18callWithStackShellFNbMDFNbPvZvZv,@function
-#if defined( USE_ABI_2 )
-    .section .text._D4core6thread18callWithStackShellFNbMDFNbPvZvZv,"a",@progbits
-#else
-    .section .opd,"aw",@progbits
-#endif
-_D4core6thread18callWithStackShellFNbMDFNbPvZvZv:
-#if !defined( USE_ABI_2 )
-    .align  3
-    .quad .L._D4core6thread18callWithStackShellFNbMDFNbPvZvZv
-    .quad .TOC.@tocbase
-    .quad 0
-#endif
-    .text
-/*
- * Called with:
- * r3: pointer context
- * r4: pointer to function
- */
-.L._D4core6thread18callWithStackShellFNbMDFNbPvZvZv:
-    .cfi_startproc
-    stdu    1, -STACK_SZ(1)
-    mflr    0
-    std     0, LR_OFS(1)
-    .cfi_def_cfa_offset 256
-    .cfi_offset lr, 16
-
-    /* Save r14-r31 in general register save area */
-    std     14, (OFS_R14_R31 + 0 * 8)(1)
-    std     15, (OFS_R14_R31 + 1 * 8)(1)
-    std     16, (OFS_R14_R31 + 2 * 8)(1)
-    std     17, (OFS_R14_R31 + 3 * 8)(1)
-    std     18, (OFS_R14_R31 + 4 * 8)(1)
-    std     19, (OFS_R14_R31 + 5 * 8)(1)
-    std     20, (OFS_R14_R31 + 6 * 8)(1)
-    std     21, (OFS_R14_R31 + 7 * 8)(1)
-    std     22, (OFS_R14_R31 + 8 * 8)(1)
-    std     23, (OFS_R14_R31 + 9 * 8)(1)
-    std     24, (OFS_R14_R31 + 10 * 8)(1)
-    std     25, (OFS_R14_R31 + 11 * 8)(1)
-    std     26, (OFS_R14_R31 + 12 * 8)(1)
-    std     27, (OFS_R14_R31 + 13 * 8)(1)
-    std     28, (OFS_R14_R31 + 14 * 8)(1)
-    std     29, (OFS_R14_R31 + 15 * 8)(1)
-    std     30, (OFS_R14_R31 + 16 * 8)(1)
-    std     31, (OFS_R14_R31 + 17 * 8)(1)
-
-    /* Save r3-r10 in parameter save area of caller */
-    std     3, (OFS_R3_R10 + 0 * 8)(1)
-    std     4, (OFS_R3_R10 + 1 * 8)(1)
-    std     5, (OFS_R3_R10 + 2 * 8)(1)
-    std     6, (OFS_R3_R10 + 3 * 8)(1)
-    std     7, (OFS_R3_R10 + 4 * 8)(1)
-    std     8, (OFS_R3_R10 + 5 * 8)(1)
-    std     9, (OFS_R3_R10 + 6 * 8)(1)
-    std     10, (OFS_R3_R10 + 7 * 8)(1)
-
-    /* Save r2 in TOC save area */
-    std     2, TOC_OFS(1)
-
-    /* Do not save r11, r12 and r13. */
-
-    /* Call delegate:
-     * r3: pointer to context
-     * r4: pointer to stack
-     */
-    mr      5, 4
-    mr      4, 1
-    ld      6, 0(5)
-    ld      11, 16(5)
-    ld      2, 8(5)
-    mtctr   6
-    bctrl
-    nop
-
-    /* Restore r2 from TOC save area */
-    ld      2, TOC_OFS(1)
-
-    /* Restore r3-r10 from local variable space */
-    ld      3, (OFS_R3_R10 + 0 * 8)(1)
-    ld      4, (OFS_R3_R10 + 1 * 8)(1)
-    ld      5, (OFS_R3_R10 + 2 * 8)(1)
-    ld      6, (OFS_R3_R10 + 3 * 8)(1)
-    ld      7, (OFS_R3_R10 + 4 * 8)(1)
-    ld      8, (OFS_R3_R10 + 5 * 8)(1)
-    ld      9, (OFS_R3_R10 + 6 * 8)(1)
-    ld      10, (OFS_R3_R10 + 7 * 8)(1)
-
-    /* Restore r14-r31 from general register save area */
-    ld      14, (OFS_R14_R31 + 0 * 8)(1)
-    ld      15, (OFS_R14_R31 + 1 * 8)(1)
-    ld      16, (OFS_R14_R31 + 2 * 8)(1)
-    ld      17, (OFS_R14_R31 + 3 * 8)(1)
-    ld      18, (OFS_R14_R31 + 4 * 8)(1)
-    ld      19, (OFS_R14_R31 + 5 * 8)(1)
-    ld      20, (OFS_R14_R31 + 6 * 8)(1)
-    ld      21, (OFS_R14_R31 + 7 * 8)(1)
-    ld      22, (OFS_R14_R31 + 8 * 8)(1)
-    ld      23, (OFS_R14_R31 + 9 * 8)(1)
-    ld      24, (OFS_R14_R31 + 10 * 8)(1)
-    ld      25, (OFS_R14_R31 + 11 * 8)(1)
-    ld      26, (OFS_R14_R31 + 12 * 8)(1)
-    ld      27, (OFS_R14_R31 + 13 * 8)(1)
-    ld      28, (OFS_R14_R31 + 14 * 8)(1)
-    ld      29, (OFS_R14_R31 + 15 * 8)(1)
-    ld      30, (OFS_R14_R31 + 16 * 8)(1)
-    ld      31, (OFS_R14_R31 + 17 * 8)(1)
-
-    ld      0, LR_OFS(1)
-    mtlr    0
-    addi    1, 1, STACK_SZ
-    blr
-    .long 0
-    .quad 0
-.Lend:
-    .size _D4core6thread18callWithStackShellFNbMDFNbPvZvZv, .Lend-.L._D4core6thread18callWithStackShellFNbMDFNbPvZvZv
-    .cfi_endproc
-
-#endif /* defined(__PPC64__) */
diff --git a/libphobos/libdruntime/config/powerpc/switchcontext.S b/libphobos/libdruntime/config/powerpc/switchcontext.S
index 0a6cc243942..6689217ca07 100644
--- a/libphobos/libdruntime/config/powerpc/switchcontext.S
+++ b/libphobos/libdruntime/config/powerpc/switchcontext.S
@@ -34,10 +34,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  *
  */
     .text
-    .globl CSYM(_fiber_switchContext)
-    .type CSYM(_fiber_switchContext), @function
+    .globl CSYM(fiber_switchContext)
+    .type CSYM(fiber_switchContext), @function
     .align 2
-CSYM(_fiber_switchContext):
+CSYM(fiber_switchContext):
     .cfi_startproc
     /* Save linkage area */
     mflr        0
@@ -149,6 +149,6 @@ CSYM(_fiber_switchContext):
     /* Return and switch context */
     blr
     .cfi_endproc
-    .size CSYM(_fiber_switchContext),.-CSYM(_fiber_switchContext)
+    .size CSYM(fiber_switchContext),.-CSYM(fiber_switchContext)
 
 #endif /* !defined(__PPC64__) */
diff --git a/libphobos/libdruntime/core/internal/convert.d b/libphobos/libdruntime/core/internal/convert.d
index 0f540f83d42..8010ad773b8 100644
--- a/libphobos/libdruntime/core/internal/convert.d
+++ b/libphobos/libdruntime/core/internal/convert.d
@@ -84,7 +84,10 @@ const(ubyte)[] toUbyte(T)(const ref T val) if (is(Unqual!T == float) || is(Unqua
             ubyte[] buff = ctfe_alloc(T.sizeof);
             enum msbSize = double.sizeof;
 
-            double hi = toPrec!double(val);
+            static if (is(Unqual!T == ireal))
+                double hi = toPrec!double(val.im);
+            else
+                double hi = toPrec!double(val);
             buff[0 .. msbSize] = toUbyte(hi)[];
 
             if (val is cast(T)0.0 || val is cast(T)-0.0 ||
@@ -98,7 +101,10 @@ const(ubyte)[] toUbyte(T)(const ref T val) if (is(Unqual!T == float) || is(Unqua
             }
             else
             {
-                double low = toPrec!double(val - hi);
+                static if (is(Unqual!T == ireal))
+                    double low = toPrec!double(val.im - hi);
+                else
+                    double low = toPrec!double(val - hi);
                 buff[msbSize .. $] = toUbyte(low)[];
             }
 
diff --git a/libphobos/libdruntime/core/sys/posix/sys/stat.d b/libphobos/libdruntime/core/sys/posix/sys/stat.d
index b0d57f28ee6..b154e1489a6 100644
--- a/libphobos/libdruntime/core/sys/posix/sys/stat.d
+++ b/libphobos/libdruntime/core/sys/posix/sys/stat.d
@@ -1391,6 +1391,7 @@ else version (Solaris)
             dev_t st_rdev;
             c_long[2] st_pad2;
             off_t st_size;
+            c_long st_pad3;
             union
             {
                 timestruc_t st_atim;
@@ -1424,7 +1425,6 @@ else version (Solaris)
             dev_t st_rdev;
             c_long[2] st_pad2;
             off64_t st_size;
-            c_long st_pad3;
             union
             {
                 timestruc_t st_atim;
diff --git a/libphobos/libdruntime/core/thread.d b/libphobos/libdruntime/core/thread.d
index fb5f942e551..e1a68057ca1 100644
--- a/libphobos/libdruntime/core/thread.d
+++ b/libphobos/libdruntime/core/thread.d
@@ -2407,93 +2407,84 @@ shared static ~this()
 // Used for needLock below.
 private __gshared bool multiThreadedFlag = false;
 
-version (PPC64) version = ExternStackShell;
-
-version (ExternStackShell)
+// Calls the given delegate, passing the current thread's stack pointer to it.
+private void callWithStackShell(scope void delegate(void* sp) nothrow fn) nothrow
+in
 {
-    extern(D) public void callWithStackShell(scope void delegate(void* sp) nothrow fn) nothrow;
+    assert(fn);
 }
-else
+body
 {
-    // Calls the given delegate, passing the current thread's stack pointer to it.
-    private void callWithStackShell(scope void delegate(void* sp) nothrow fn) nothrow
-    in
+    // The purpose of the 'shell' is to ensure all the registers get
+    // put on the stack so they'll be scanned. We only need to push
+    // the callee-save registers.
+    void *sp = void;
+
+    version (GNU)
     {
-        assert(fn);
+        __builtin_unwind_init();
+        sp = &sp;
     }
-    body
+    else version (AsmX86_Posix)
     {
-        // The purpose of the 'shell' is to ensure all the registers get
-        // put on the stack so they'll be scanned. We only need to push
-        // the callee-save registers.
-        void *sp = void;
-
-        version (GNU)
-        {
-            __builtin_unwind_init();
-            sp = &sp;
-        }
-        else version (AsmX86_Posix)
+        size_t[3] regs = void;
+        asm pure nothrow @nogc
         {
-            size_t[3] regs = void;
-            asm pure nothrow @nogc
-            {
-                mov [regs + 0 * 4], EBX;
-                mov [regs + 1 * 4], ESI;
-                mov [regs + 2 * 4], EDI;
+            mov [regs + 0 * 4], EBX;
+            mov [regs + 1 * 4], ESI;
+            mov [regs + 2 * 4], EDI;
 
-                mov sp[EBP], ESP;
-            }
+            mov sp[EBP], ESP;
         }
-        else version (AsmX86_Windows)
+    }
+    else version (AsmX86_Windows)
+    {
+        size_t[3] regs = void;
+        asm pure nothrow @nogc
         {
-            size_t[3] regs = void;
-            asm pure nothrow @nogc
-            {
-                mov [regs + 0 * 4], EBX;
-                mov [regs + 1 * 4], ESI;
-                mov [regs + 2 * 4], EDI;
+            mov [regs + 0 * 4], EBX;
+            mov [regs + 1 * 4], ESI;
+            mov [regs + 2 * 4], EDI;
 
-                mov sp[EBP], ESP;
-            }
+            mov sp[EBP], ESP;
         }
-        else version (AsmX86_64_Posix)
+    }
+    else version (AsmX86_64_Posix)
+    {
+        size_t[5] regs = void;
+        asm pure nothrow @nogc
         {
-            size_t[5] regs = void;
-            asm pure nothrow @nogc
-            {
-                mov [regs + 0 * 8], RBX;
-                mov [regs + 1 * 8], R12;
-                mov [regs + 2 * 8], R13;
-                mov [regs + 3 * 8], R14;
-                mov [regs + 4 * 8], R15;
+            mov [regs + 0 * 8], RBX;
+            mov [regs + 1 * 8], R12;
+            mov [regs + 2 * 8], R13;
+            mov [regs + 3 * 8], R14;
+            mov [regs + 4 * 8], R15;
 
-                mov sp[RBP], RSP;
-            }
+            mov sp[RBP], RSP;
         }
-        else version (AsmX86_64_Windows)
-        {
-            size_t[7] regs = void;
-            asm pure nothrow @nogc
-            {
-                mov [regs + 0 * 8], RBX;
-                mov [regs + 1 * 8], RSI;
-                mov [regs + 2 * 8], RDI;
-                mov [regs + 3 * 8], R12;
-                mov [regs + 4 * 8], R13;
-                mov [regs + 5 * 8], R14;
-                mov [regs + 6 * 8], R15;
-
-                mov sp[RBP], RSP;
-            }
-        }
-        else
+    }
+    else version (AsmX86_64_Windows)
+    {
+        size_t[7] regs = void;
+        asm pure nothrow @nogc
         {
-            static assert(false, "Architecture not supported.");
-        }
+            mov [regs + 0 * 8], RBX;
+            mov [regs + 1 * 8], RSI;
+            mov [regs + 2 * 8], RDI;
+            mov [regs + 3 * 8], R12;
+            mov [regs + 4 * 8], R13;
+            mov [regs + 5 * 8], R14;
+            mov [regs + 6 * 8], R15;
 
-        fn(sp);
+            mov sp[RBP], RSP;
+        }
     }
+    else
+    {
+        static assert(false, "Architecture not supported.");
+    }
+
+    fn(sp);
 }
 
 // Used for suspendAll/resumeAll below.
@@ -5287,6 +5278,23 @@ unittest
 
 
 // Multiple threads running shared fibers
+version (PPC)   version = UnsafeFiberMigration;
+version (PPC64) version = UnsafeFiberMigration;
+
+version (UnsafeFiberMigration)
+{
+    // XBUG: core.thread fibers are supposed to be safe to migrate across
+    // threads, however, there is a problem: GCC always assumes that the
+    // address of thread-local variables don't change while on a given stack.
+    // In consequence, migrating fibers between threads currently is an unsafe
+    // thing to do, and will break on some targets (possibly PR26461).
+}
+else
+{
+    version = FiberMigrationUnittest;
+}
+
+version (FiberMigrationUnittest)
 unittest
 {
     shared bool[10] locks;
diff --git a/libphobos/testsuite/libphobos.thread/fiber_guard_page.d b/libphobos/testsuite/libphobos.thread/fiber_guard_page.d
index 49c22658542..61a616acd8e 100644
--- a/libphobos/testsuite/libphobos.thread/fiber_guard_page.d
+++ b/libphobos/testsuite/libphobos.thread/fiber_guard_page.d
@@ -18,7 +18,7 @@ void stackMethod()
 
 void main()
 {
-    auto test_fiber = new Fiber(&stackMethod, stackSize);
+    auto test_fiber = new Fiber(&stackMethod, stackSize, stackSize);
 
     // allocate a page below (above) the fiber's stack to make stack overflows possible (w/o segfaulting)
     version (StackGrowsDown)