gcc: xtensa: add -mabi option for call0/windowed ABI

2020-06-15  Max Filippov  <jcmvbkbc@gmail.com>
gcc/
	* config/xtensa/elf.h (ASM_SPEC, LINK_SPEC): Pass ABI switch to
	assembler/linker.
	* config/xtensa/linux.h (ASM_SPEC, LINK_SPEC): Ditto.
	* config/xtensa/uclinux.h (ASM_SPEC, LINK_SPEC): Ditto.
	* config/xtensa/xtensa.c (xtensa_option_override): Initialize
	xtensa_windowed_abi if needed.
	* config/xtensa/xtensa.h (TARGET_WINDOWED_ABI_DEFAULT): New
	macro.
	(TARGET_WINDOWED_ABI): Redefine to xtensa_windowed_abi.
	* config/xtensa/xtensa.opt (xtensa_windowed_abi): New target
	option variable.
	(mabi=call0, mabi=windowed): New options.
	* doc/invoke.texi: Document new -mabi= Xtensa-specific options.

gcc/testsuite/
	* gcc.target/xtensa/mabi-call0.c: New test.
	* gcc.target/xtensa/mabi-windowed.c: New test.

libgcc/
	* configure: Regenerate.
	* configure.ac: Use AC_COMPILE_IFELSE instead of manual
	preprocessor invocation to check for __XTENSA_CALL0_ABI__.

9 files changed, 86 insertions, 8 deletions

diff --git a/gcc/config/xtensa/elf.h b/gcc/config/xtensa/elf.h
index 6fd589f..48e2590 100644
--- a/gcc/config/xtensa/elf.h
+++ b/gcc/config/xtensa/elf.h
@@ -47,7 +47,9 @@ along with GCC; see the file COPYING3.  If not see
   %{mlongcalls:--longcalls} \
   %{mno-longcalls:--no-longcalls} \
   %{mauto-litpools:--auto-litpools} \
-  %{mno-auto-litpools:--no-auto-litpools}"
+  %{mno-auto-litpools:--no-auto-litpools} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #undef LIB_SPEC
 #define LIB_SPEC "-lc -lsim -lc -lhandlers-sim -lhal"
@@ -65,7 +67,9 @@ along with GCC; see the file COPYING3.  If not see
   %{!shared: \
     %{!static: \
       %{rdynamic:-export-dynamic} \
-    %{static:-static}}}"
+    %{static:-static}}} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #undef LOCAL_LABEL_PREFIX
 #define LOCAL_LABEL_PREFIX	"."
diff --git a/gcc/config/xtensa/linux.h b/gcc/config/xtensa/linux.h
index 62a33a9..bd20595 100644
--- a/gcc/config/xtensa/linux.h
+++ b/gcc/config/xtensa/linux.h
@@ -44,7 +44,9 @@ along with GCC; see the file COPYING3.  If not see
   %{mlongcalls:--longcalls} \
   %{mno-longcalls:--no-longcalls} \
   %{mauto-litpools:--auto-litpools} \
-  %{mno-auto-litpools:--no-auto-litpools}"
+  %{mno-auto-litpools:--no-auto-litpools} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
 
@@ -55,7 +57,9 @@ along with GCC; see the file COPYING3.  If not see
     %{!static: \
       %{rdynamic:-export-dynamic} \
       -dynamic-linker " GNU_USER_DYNAMIC_LINKER "} \
-    %{static:-static}}"
+    %{static:-static}} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #undef LOCAL_LABEL_PREFIX
 #define LOCAL_LABEL_PREFIX	"."
diff --git a/gcc/config/xtensa/uclinux.h b/gcc/config/xtensa/uclinux.h
index 64ba26f..374d2947 100644
--- a/gcc/config/xtensa/uclinux.h
+++ b/gcc/config/xtensa/uclinux.h
@@ -51,10 +51,15 @@ along with GCC; see the file COPYING3.  If not see
   %{mlongcalls:--longcalls} \
   %{mno-longcalls:--no-longcalls} \
   %{mauto-litpools:--auto-litpools} \
-  %{mno-auto-litpools:--no-auto-litpools}"
+  %{mno-auto-litpools:--no-auto-litpools} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #undef LINK_SPEC
-#define LINK_SPEC "%{!no-elf2flt:%{!elf2flt*:-elf2flt}}"
+#define LINK_SPEC \
+ "%{!no-elf2flt:%{!elf2flt*:-elf2flt}} \
+  %{mabi=windowed:--abi-windowed} \
+  %{mabi=call0:--abi-call0}"
 
 #undef LOCAL_LABEL_PREFIX
 #define LOCAL_LABEL_PREFIX	"."
diff --git a/gcc/config/xtensa/xtensa.c b/gcc/config/xtensa/xtensa.c
index e3afb70..e370aa4 100644
--- a/gcc/config/xtensa/xtensa.c
+++ b/gcc/config/xtensa/xtensa.c
@@ -2219,6 +2219,9 @@ xtensa_option_override (void)
   int regno;
   machine_mode mode;
 
+  if (xtensa_windowed_abi == -1)
+    xtensa_windowed_abi = TARGET_WINDOWED_ABI_DEFAULT;
+
   /* Use CONST16 in the absence of L32R.
      Set it in the TARGET_OPTION_OVERRIDE to avoid dependency on xtensa
      configuration in the xtensa-common.c  */
diff --git a/gcc/config/xtensa/xtensa.h b/gcc/config/xtensa/xtensa.h
index fb5aee8..33bfe45 100644
--- a/gcc/config/xtensa/xtensa.h
+++ b/gcc/config/xtensa/xtensa.h
@@ -64,7 +64,8 @@ along with GCC; see the file COPYING3.  If not see
 #define TARGET_ABSOLUTE_LITERALS XSHAL_USE_ABSOLUTE_LITERALS
 #define TARGET_THREADPTR	XCHAL_HAVE_THREADPTR
 #define TARGET_LOOPS	        XCHAL_HAVE_LOOPS
-#define TARGET_WINDOWED_ABI	(XSHAL_ABI == XTHAL_ABI_WINDOWED)
+#define TARGET_WINDOWED_ABI_DEFAULT (XSHAL_ABI == XTHAL_ABI_WINDOWED)
+#define TARGET_WINDOWED_ABI	xtensa_windowed_abi
 #define TARGET_DEBUG		XCHAL_HAVE_DEBUG
 #define TARGET_L32R		XCHAL_HAVE_L32R
 
diff --git a/gcc/config/xtensa/xtensa.opt b/gcc/config/xtensa/xtensa.opt
index dd7aba4..0c4aa92 100644
--- a/gcc/config/xtensa/xtensa.opt
+++ b/gcc/config/xtensa/xtensa.opt
@@ -45,3 +45,14 @@ Relax literals in assembler and place them automatically in the text section.
 mserialize-volatile
 Target Report Mask(SERIALIZE_VOLATILE)
 -mno-serialize-volatile	Do not serialize volatile memory references with MEMW instructions.
+
+TargetVariable
+int xtensa_windowed_abi = -1
+
+mabi=call0
+Target Report RejectNegative Var(xtensa_windowed_abi, 0)
+Use call0 ABI.
+
+mabi=windowed
+Target Report RejectNegative Var(xtensa_windowed_abi, 1)
+Use windowed registers ABI.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 06a04e3..74ab149 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1386,7 +1386,8 @@ See RS/6000 and PowerPC Options.
 -mtext-section-literals  -mno-text-section-literals @gol
 -mauto-litpools  -mno-auto-litpools @gol
 -mtarget-align  -mno-target-align @gol
--mlongcalls  -mno-longcalls}
+-mlongcalls  -mno-longcalls @gol
+-mabi=@var{abi-type}}
 
 @emph{zSeries Options}
 See S/390 and zSeries Options.
@@ -30780,6 +30781,29 @@ assembly code generated by GCC still shows direct call
 instructions---look at the disassembled object code to see the actual
 instructions.  Note that the assembler uses an indirect call for
 every cross-file call, not just those that really are out of range.
+
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified ABI@.  Permissible values are: @samp{call0},
+@samp{windowed}.  Default ABI is chosen by the Xtensa core configuration.
+
+@item -mabi=call0
+@opindex mabi=call0
+When this option is enabled function parameters are passed in registers
+@code{a2} through @code{a7}, registers @code{a12} through @code{a15} are
+caller-saved, and register @code{a15} may be used as a frame pointer.
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__XTENSA_CALL0_ABI__} is defined.
+
+@item -mabi=windowed
+@opindex mabi=windowed
+When this option is enabled function parameters are passed in registers
+@code{a10} through @code{a15}, and called function rotates register window
+by 8 registers on entry so that its arguments are found in registers
+@code{a2} through @code{a7}.  Register @code{a7} may be used as a frame
+pointer.  Register window is rotated 8 registers back upon return.
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__XTENSA_WINDOWED_ABI__} is defined.
 @end table
 
 @node zSeries Options
diff --git a/gcc/testsuite/gcc.target/xtensa/mabi-call0.c b/gcc/testsuite/gcc.target/xtensa/mabi-call0.c
new file mode 100644
index 0000000..65d7295
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xtensa/mabi-call0.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-mabi=call0" } */
+
+#ifndef __XTENSA_CALL0_ABI__
+#error
+#endif
+
+void foo(void)
+{
+}
+
+/* { dg-final { scan-assembler-not "entry" } } */
+/* { dg-final { scan-assembler-not "retw" } } */
diff --git a/gcc/testsuite/gcc.target/xtensa/mabi-windowed.c b/gcc/testsuite/gcc.target/xtensa/mabi-windowed.c
new file mode 100644
index 0000000..aaddf41
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xtensa/mabi-windowed.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-mabi=windowed" } */
+
+#ifndef __XTENSA_WINDOWED_ABI__
+#error
+#endif
+
+void foo(void)
+{
+}
+
+/* { dg-final { scan-assembler "entry" } } */
+/* { dg-final { scan-assembler "retw" } } */