Add a new attribute called 'jumptable' that creates jump-instruction tables for functions marked with this attribute.

It includes a pass that rewrites all indirect calls to jumptable functions to pass through these tables.

This also adds backend support for generating the jump-instruction tables on ARM and X86.
Note that since the jumptable attribute creates a second function pointer for a
function, any function marked with jumptable must also be marked with unnamed_addr.

llvm-svn: 210280

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/jump_tables.ll b/llvm/test/CodeGen/ARM/jump_tables.ll
new file mode 100644
index 00000000000..61c7e43adfe
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/jump_tables.ll
@@ -0,0 +1,32 @@
+; RUN: llc <%s -march=arm -jump-table-type=single | FileCheck --check-prefix=ARM %s
+; RUN: llc <%s -march=thumb -jump-table-type=single | FileCheck --check-prefix=THUMB %s
+
+define void @indirect_fun() unnamed_addr jumptable {
+  ret void
+}
+define void ()* @get_fun() {
+  ret void ()* @indirect_fun
+
+; ARM:         ldr     r0, [[LABEL:.*]]
+; ARM:         mov     pc, lr
+; ARM: [[LABEL]]:
+; ARM:         .long   __llvm_jump_instr_table_0_1
+
+; THUMB:         ldr     r0, [[LABEL:.*]]
+; THUMB:         bx      lr
+; THUMB: [[LABEL]]:
+; THUMB:         .long   __llvm_jump_instr_table_0_1
+}
+
+; ARM:         .globl  __llvm_jump_instr_table_0_1
+; ARM:         .align  3
+; ARM:         .type   __llvm_jump_instr_table_0_1,%function
+; ARM: __llvm_jump_instr_table_0_1:
+; ARM:         b     indirect_fun(PLT)
+
+; THUMB:         .globl  __llvm_jump_instr_table_0_1
+; THUMB:         .align  3
+; THUMB:         .thumb_func
+; THUMB:         .type   __llvm_jump_instr_table_0_1,%function
+; THUMB: __llvm_jump_instr_table_0_1:
+; THUMB:         b     indirect_fun(PLT)