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/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 7595ae05..a02f32f 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1131,6 +1131,14 @@
return false;
}
+ // FIXME: Can we support the fallthrough edge?
+ if (isa<CallBrInst>(Pred->getTerminator())) {
+ LLVM_DEBUG(
+ dbgs() << "COULD NOT PRE LOAD BECAUSE OF CALLBR CRITICAL EDGE '"
+ << Pred->getName() << "': " << *LI << '\n');
+ return false;
+ }
+
if (LoadBB->isEHPad()) {
LLVM_DEBUG(
dbgs() << "COULD NOT PRE LOAD BECAUSE OF AN EH PAD CRITICAL EDGE '"
@@ -2167,8 +2175,8 @@
return false;
// We don't currently value number ANY inline asm calls.
- if (CallInst *CallI = dyn_cast<CallInst>(CurInst))
- if (CallI->isInlineAsm())
+ if (auto *CallB = dyn_cast<CallBase>(CurInst))
+ if (CallB->isInlineAsm())
return false;
uint32_t ValNo = VN.lookup(CurInst);
@@ -2251,6 +2259,11 @@
if (isa<IndirectBrInst>(PREPred->getTerminator()))
return false;
+ // Don't do PRE across callbr.
+ // FIXME: Can we do this across the fallthrough edge?
+ if (isa<CallBrInst>(PREPred->getTerminator()))
+ return false;
+
// We can't do PRE safely on a critical edge, so instead we schedule
// the edge to be split and perform the PRE the next time we iterate
// on the function.