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/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 3fec17a..00bcb84 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1265,8 +1265,10 @@
while (isa<DbgInfoIntrinsic>(I2))
I2 = &*BB2_Itr++;
}
+ // FIXME: Can we define a safety predicate for CallBr?
if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) ||
- (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
+ (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)) ||
+ isa<CallBrInst>(I1))
return false;
BasicBlock *BIParent = BI->getParent();
@@ -1349,9 +1351,14 @@
HoistTerminator:
// It may not be possible to hoist an invoke.
+ // FIXME: Can we define a safety predicate for CallBr?
if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
return Changed;
+ // TODO: callbr hoisting currently disabled pending further study.
+ if (isa<CallBrInst>(I1))
+ return Changed;
+
for (BasicBlock *Succ : successors(BB1)) {
for (PHINode &PN : Succ->phis()) {
Value *BB1V = PN.getIncomingValueForBlock(BB1);
@@ -1443,7 +1450,7 @@
// Conservatively return false if I is an inline-asm instruction. Sinking
// and merging inline-asm instructions can potentially create arguments
// that cannot satisfy the inline-asm constraints.
- if (const auto *C = dyn_cast<CallInst>(I))
+ if (const auto *C = dyn_cast<CallBase>(I))
if (C->isInlineAsm())
return false;
@@ -1506,7 +1513,7 @@
// We can't create a PHI from this GEP.
return false;
// Don't create indirect calls! The called value is the final operand.
- if ((isa<CallInst>(I0) || isa<InvokeInst>(I0)) && OI == OE - 1) {
+ if (isa<CallBase>(I0) && OI == OE - 1) {
// FIXME: if the call was *already* indirect, we should do this.
return false;
}