Index: compiler-rt/lib/builtins/CMakeLists.txt
===================================================================
--- compiler-rt/lib/builtins/CMakeLists.txt
+++ compiler-rt/lib/builtins/CMakeLists.txt
@@ -638,6 +638,7 @@
 set(riscv_SOURCES
   riscv/save.S
   riscv/restore.S
+  riscv/restore_tailcall.S
   ${GENERIC_SOURCES}
   ${GENERIC_TF_SOURCES}
 )
Index: compiler-rt/lib/builtins/riscv/restore_tailcall.S
===================================================================
--- /dev/null
+++ compiler-rt/lib/builtins/riscv/restore_tailcall.S
@@ -0,0 +1,293 @@
+//===-- restore_tailcall.S - restore up to 12 callee-save registers -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Multiple entry points depending on number of registers to restore. Restores
+// registers and then performs a tail call.
+//
+//===----------------------------------------------------------------------===//
+
+// These are alternative entry points to the normal __riscv_restore_<N>
+// functions which allow the save-restore mechnism to be used even when the
+// caller is making a tail call. These entry points take a single argument
+// in `t1` which is the address of the function to jump to after restoring
+// the registers and stack pointer.
+
+// All of the entry points are in the same section since we rely on many of
+// them falling through into each other and don't want the linker to
+// accidentally split them up, garbage collect, or reorder them.
+//
+// The entry points are grouped up into 2s for rv64 and 4s for rv32 since this
+// is the minimum grouping which will maintain the required 16-byte stack
+// alignment.
+
+  .text
+
+#if __riscv_xlen == 32
+
+  .globl  __riscv_restore_tailcall_12
+  .type   __riscv_restore_tailcall_12,@function
+__riscv_restore_tailcall_12:
+  .cfi_startproc
+  .cfi_def_cfa_offset 64
+  .cfi_offset s11, -64+12
+  .cfi_offset s10, -64+16
+  .cfi_offset s9, -64+20
+  .cfi_offset s8, -64+24
+  .cfi_offset s7, -64+28
+  .cfi_offset s6, -64+32
+  .cfi_offset s5, -64+36
+  .cfi_offset s4, -64+40
+  .cfi_offset s3, -64+44
+  .cfi_offset s2, -64+48
+  .cfi_offset s1, -64+52
+  .cfi_offset s0, -64+56
+  .cfi_offset ra, -64+60
+  lw      s11, 12(sp)
+  .cfi_restore s11
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_11/10/9/8
+
+  .globl  __riscv_restore_tailcall_11
+  .type   __riscv_restore_tailcall_11,@function
+  .globl  __riscv_restore_tailcall_10
+  .type   __riscv_restore_tailcall_10,@function
+  .globl  __riscv_restore_tailcall_9
+  .type   __riscv_restore_tailcall_9,@function
+  .globl  __riscv_restore_tailcall_8
+  .type   __riscv_restore_tailcall_8,@function
+__riscv_restore_tailcall_11:
+__riscv_restore_tailcall_10:
+__riscv_restore_tailcall_9:
+__riscv_restore_tailcall_8:
+  .cfi_restore s11
+  .cfi_def_cfa_offset 48
+  lw      s10, 0(sp)
+  .cfi_restore s10
+  lw      s9,  4(sp)
+  .cfi_restore s9
+  lw      s8,  8(sp)
+  .cfi_restore s8
+  lw      s7,  12(sp)
+  .cfi_restore s7
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_7/6/5/4
+
+  .globl  __riscv_restore_tailcall_7
+  .type   __riscv_restore_tailcall_7,@function
+  .globl  __riscv_restore_tailcall_6
+  .type   __riscv_restore_tailcall_6,@function
+  .globl  __riscv_restore_tailcall_5
+  .type   __riscv_restore_tailcall_5,@function
+  .globl  __riscv_restore_tailcall_4
+  .type   __riscv_restore_tailcall_4,@function
+__riscv_restore_tailcall_7:
+__riscv_restore_tailcall_6:
+__riscv_restore_tailcall_5:
+__riscv_restore_tailcall_4:
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 32
+  lw      s6,  0(sp)
+  .cfi_restore s6
+  lw      s5,  4(sp)
+  .cfi_restore s5
+  lw      s4,  8(sp)
+  .cfi_restore s4
+  lw      s3,  12(sp)
+  .cfi_restore s3
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_3/2/1/0
+
+  .globl  __riscv_restore_tailcall_3
+  .type   __riscv_restore_tailcall_3,@function
+  .globl  __riscv_restore_tailcall_2
+  .type   __riscv_restore_tailcall_2,@function
+  .globl  __riscv_restore_tailcall_1
+  .type   __riscv_restore_tailcall_1,@function
+  .globl  __riscv_restore_tailcall_0
+  .type   __riscv_restore_tailcall_0,@function
+__riscv_restore_tailcall_3:
+__riscv_restore_tailcall_2:
+__riscv_restore_tailcall_1:
+__riscv_restore_tailcall_0:
+  .cfi_restore s3
+  .cfi_restore s4
+  .cfi_restore s5
+  .cfi_restore s6
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 16
+  lw      s2,  0(sp)
+  .cfi_restore s2
+  lw      s1,  4(sp)
+  .cfi_restore s1
+  lw      s0,  8(sp)
+  .cfi_restore s0
+  lw      ra,  12(sp)
+  .cfi_restore ra
+  addi    sp, sp, 16
+  .cfi_def_cfa_offset 0
+  jr      t1
+  .cfi_endproc
+
+#elif __riscv_xlen == 64
+
+  .globl  __riscv_restore_tailcall_12
+  .type   __riscv_restore_tailcall_12,@function
+__riscv_restore_tailcall_12:
+  .cfi_startproc
+  .cfi_def_cfa_offset 112
+  .cfi_offset s11, -112+8
+  .cfi_offset s10, -112+16
+  .cfi_offset s9, -112+24
+  .cfi_offset s8, -112+32
+  .cfi_offset s7, -112+40
+  .cfi_offset s6, -112+48
+  .cfi_offset s5, -112+56
+  .cfi_offset s4, -112+64
+  .cfi_offset s3, -112+72
+  .cfi_offset s2, -112+80
+  .cfi_offset s1, -112+88
+  .cfi_offset s0, -112+96
+  .cfi_offset ra, -112+104
+  ld      s11, 8(sp)
+  .cfi_restore s11
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_11/10
+
+  .globl  __riscv_restore_tailcall_11
+  .type   __riscv_restore_tailcall_11,@function
+  .globl  __riscv_restore_tailcall_10
+  .type   __riscv_restore_tailcall_10,@function
+__riscv_restore_tailcall_11:
+__riscv_restore_tailcall_10:
+  .cfi_restore s11
+  .cfi_def_cfa_offset 96
+  ld      s10, 0(sp)
+  .cfi_restore s10
+  ld      s9,  8(sp)
+  .cfi_restore s9
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_9/8
+
+  .globl  __riscv_restore_tailcall_9
+  .type   __riscv_restore_tailcall_9,@function
+  .globl  __riscv_restore_tailcall_8
+  .type   __riscv_restore_tailcall_8,@function
+__riscv_restore_tailcall_9:
+__riscv_restore_tailcall_8:
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 80
+  ld      s8,  0(sp)
+  .cfi_restore s8
+  ld      s7,  8(sp)
+  .cfi_restore s7
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_7/6
+
+  .globl  __riscv_restore_tailcall_7
+  .type   __riscv_restore_tailcall_7,@function
+  .globl  __riscv_restore_tailcall_6
+  .type   __riscv_restore_tailcall_6,@function
+__riscv_restore_tailcall_7:
+__riscv_restore_tailcall_6:
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 64
+  ld      s6,  0(sp)
+  .cfi_restore s6
+  ld      s5,  8(sp)
+  .cfi_restore s5
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_5/4
+
+  .globl  __riscv_restore_tailcall_5
+  .type   __riscv_restore_tailcall_5,@function
+  .globl  __riscv_restore_tailcall_4
+  .type   __riscv_restore_tailcall_4,@function
+__riscv_restore_tailcall_5:
+__riscv_restore_tailcall_4:
+  .cfi_restore s5
+  .cfi_restore s6
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 48
+  ld      s4,  0(sp)
+  .cfi_restore s4
+  ld      s3,  8(sp)
+  .cfi_restore s3
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_3/2
+
+  .globl  __riscv_restore_tailcall_3
+  .type   __riscv_restore_tailcall_3,@function
+  .globl  __riscv_restore_tailcall_2
+  .type   __riscv_restore_tailcall_2,@function
+  .globl  __riscv_restore_tailcall_1
+  .type   __riscv_restore_tailcall_1,@function
+  .globl  __riscv_restore_tailcall_0
+  .type   __riscv_restore_tailcall_0,@function
+__riscv_restore_tailcall_3:
+__riscv_restore_tailcall_2:
+  .cfi_restore s3
+  .cfi_restore s4
+  .cfi_restore s5
+  .cfi_restore s6
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 32
+  ld      s2,  0(sp)
+  .cfi_restore s2
+  ld      s1,  8(sp)
+  .cfi_restore s1
+  addi    sp, sp, 16
+  // fallthrough into __riscv_restore_tailcall_1/0
+
+__riscv_restore_tailcall_1:
+__riscv_restore_tailcall_0:
+  .cfi_restore s1
+  .cfi_restore s2
+  .cfi_restore s3
+  .cfi_restore s4
+  .cfi_restore s5
+  .cfi_restore s6
+  .cfi_restore s7
+  .cfi_restore s8
+  .cfi_restore s9
+  .cfi_restore s10
+  .cfi_restore s11
+  .cfi_def_cfa_offset 16
+  ld      s0,  0(sp)
+  .cfi_restore s0
+  ld      ra,  8(sp)
+  .cfi_restore ra
+  addi    sp, sp, 16
+  .cfi_def_cfa_offset 0
+  jr      t1
+  .cfi_endproc
+
+#else
+# error "xlen must be 32 or 64 for save-restore implementation
+#endif