Implementation of asm-goto support in LLVM

This patch accompanies the RFC posted here:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127239.html

This patch adds a new CallBr IR instruction to support asm-goto
inline assembly like gcc as used by the linux kernel. This
instruction is both a call instruction and a terminator
instruction with multiple successors. Only inline assembly
usage is supported today.

This also adds a new INLINEASM_BR opcode to SelectionDAG and
MachineIR to represent an INLINEASM block that is also
considered a terminator instruction.

There will likely be more bug fixes and optimizations to follow
this, but we felt it had reached a point where we would like to
switch to an incremental development model.

Patch by Craig Topper, Alexander Ivchenko, Mikhail Dvoretckii

Differential Revision: https://reviews.llvm.org/D53765

llvm-svn: 353563

2 files changed, 14 insertions, 0 deletions

diff --git a/llvm/test/Bitcode/callbr.ll b/llvm/test/Bitcode/callbr.ll
new file mode 100644
index 00000000000..ecc397ac754
--- /dev/null
+++ b/llvm/test/Bitcode/callbr.ll
@@ -0,0 +1,14 @@
+; RUN:  llvm-dis < %s.bc | FileCheck %s
+
+; callbr.ll.bc was generated by passing this file to llvm-as.
+
+define i32 @test_asm_goto(i32 %x){
+entry:
+; CHECK:      callbr void asm "", "r,X"(i32 %x, i8* blockaddress(@test_asm_goto, %fail))
+; CHECK-NEXT: to label %normal [label %fail]
+  callbr void asm "", "r,X"(i32 %x, i8* blockaddress(@test_asm_goto, %fail)) to label %normal [label %fail]
+normal:
+  ret i32 1
+fail:
+  ret i32 0
+}
diff --git a/llvm/test/Bitcode/callbr.ll.bc b/llvm/test/Bitcode/callbr.ll.bc
new file mode 100644
index 00000000000..d07cba433c1
--- /dev/null
+++ b/llvm/test/Bitcode/callbr.ll.bc