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
diff --git a/llvm/lib/CodeGen/IndirectBrExpandPass.cpp b/llvm/lib/CodeGen/IndirectBrExpandPass.cpp
index 9a96abf..7ac093b 100644
--- a/llvm/lib/CodeGen/IndirectBrExpandPass.cpp
+++ b/llvm/lib/CodeGen/IndirectBrExpandPass.cpp
@@ -148,11 +148,9 @@
ConstantInt *BBIndexC = ConstantInt::get(ITy, BBIndex);
// Now rewrite the blockaddress to an integer constant based on the index.
- // FIXME: We could potentially preserve the uses as arguments to inline asm.
- // This would allow some uses such as diagnostic information in crashes to
- // have higher quality even when this transform is enabled, but would break
- // users that round-trip blockaddresses through inline assembly and then
- // back into an indirectbr.
+ // FIXME: This part doesn't properly recognize other uses of blockaddress
+ // expressions, for instance, where they are used to pass labels to
+ // asm-goto. This part of the pass needs a rework.
BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(BBIndexC, BA->getType()));
}