Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20181226' into staging

Host support for riscv64.
Dead code elimination pass.
Register allocation improvements.

# gpg: Signature made Tue 25 Dec 2018 20:52:34 GMT
# gpg:                using RSA key 64DF38E8AF7E215F
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>"
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-tcg-20181226: (42 commits)
  tcg: Improve call argument loading
  tcg: Record register preferences during liveness
  tcg: Add TCG_OPF_BB_EXIT
  tcg: Split out more subroutines from liveness_pass_1
  tcg: Rename and adjust liveness_pass_1 helpers
  tcg: Reindent parts of liveness_pass_1
  tcg: Dump register preference info with liveness
  tcg: Improve register allocation for matching constraints
  tcg: Add output_pref to TCGOp
  tcg: Add preferred_reg argument to tcg_reg_alloc_do_movi
  tcg: Add preferred_reg argument to temp_sync
  tcg: Add preferred_reg argument to temp_load
  tcg: Add preferred_reg argument to tcg_reg_alloc
  tcg: Add reachable_code_pass
  tcg: Reference count labels
  tcg: Add TCG_CALL_NO_RETURN
  tcg: Renumber TCG_CALL_* flags
  linux-user: Add safe_syscall for riscv64 host
  disas/microblaze: Remove unused REG_SP macro
  configure: Add support for building RISC-V host
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 122 insertions, 0 deletions

diff --git a/linux-user/host/riscv32/hostdep.h b/linux-user/host/riscv32/hostdep.h
new file mode 100644
index 0000000..adf9edb
--- /dev/null
+++ b/linux-user/host/riscv32/hostdep.h
@@ -0,0 +1,11 @@
+/*
+ * hostdep.h : things which are dependent on the host architecture
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef RISCV32_HOSTDEP_H
+#define RISCV32_HOSTDEP_H
+
+#endif
diff --git a/linux-user/host/riscv64/hostdep.h b/linux-user/host/riscv64/hostdep.h
new file mode 100644
index 0000000..865f0fb
--- /dev/null
+++ b/linux-user/host/riscv64/hostdep.h
@@ -0,0 +1,34 @@
+/*
+ * hostdep.h : things which are dependent on the host architecture
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef RISCV64_HOSTDEP_H
+#define RISCV64_HOSTDEP_H
+
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    ucontext_t *uc = puc;
+    unsigned long *pcreg = &uc->uc_mcontext.__gregs[REG_PC];
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
+#endif
diff --git a/linux-user/host/riscv64/safe-syscall.inc.S b/linux-user/host/riscv64/safe-syscall.inc.S
new file mode 100644
index 0000000..9ca3fbf
--- /dev/null
+++ b/linux-user/host/riscv64/safe-syscall.inc.S
@@ -0,0 +1,77 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2018 Linaro, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, @function
+	.type	safe_syscall_start, @function
+	.type	safe_syscall_end, @function
+
+	/*
+	 * This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+safe_syscall_base:
+	.cfi_startproc
+	/*
+	 * The syscall calling convention is nearly the same as C:
+	 * we enter with a0 == *signal_pending
+	 *               a1 == syscall number
+	 *               a2 ... a7 == syscall arguments
+	 *               and return the result in a0
+	 * and the syscall instruction needs
+	 *               a7 == syscall number
+	 *               a0 ... a5 == syscall arguments
+	 *               and returns the result in a0
+	 * Shuffle everything around appropriately.
+	 */
+	mv	t0, a0		/* signal_pending pointer */
+	mv	t1, a1		/* syscall number */
+	mv	a0, a2		/* syscall arguments */
+	mv	a1, a3
+	mv	a2, a4
+	mv	a3, a5
+	mv	a4, a6
+	mv	a5, a7
+	mv	a7, t1
+
+	/*
+	 * This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* If signal_pending is non-zero, don't do the call */
+	lw	t1, 0(t0)
+	bnez	t1, 0f
+	scall
+safe_syscall_end:
+	/* code path for having successfully executed the syscall */
+	ret
+
+0:
+	/* code path when we didn't execute the syscall */
+	li	a0, -TARGET_ERESTARTSYS
+	ret
+	.cfi_endproc
+
+	.size	safe_syscall_base, .-safe_syscall_base