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/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 7738a79..f74f7e2 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1055,7 +1055,7 @@
Condition = IB->getAddress()->stripPointerCasts();
Preference = WantBlockAddress;
} else {
- return false; // Must be an invoke.
+ return false; // Must be an invoke or callbr.
}
// Run constant folding to see if we can reduce the condition to a simple
@@ -1428,7 +1428,9 @@
// Add all the unavailable predecessors to the PredsToSplit list.
for (BasicBlock *P : predecessors(LoadBB)) {
// If the predecessor is an indirect goto, we can't split the edge.
- if (isa<IndirectBrInst>(P->getTerminator()))
+ // Same for CallBr.
+ if (isa<IndirectBrInst>(P->getTerminator()) ||
+ isa<CallBrInst>(P->getTerminator()))
return false;
if (!AvailablePredSet.count(P))
@@ -1641,8 +1643,9 @@
++PredWithKnownDest;
// If the predecessor ends with an indirect goto, we can't change its
- // destination.
- if (isa<IndirectBrInst>(Pred->getTerminator()))
+ // destination. Same for CallBr.
+ if (isa<IndirectBrInst>(Pred->getTerminator()) ||
+ isa<CallBrInst>(Pred->getTerminator()))
continue;
PredToDestList.push_back(std::make_pair(Pred, DestBB));