Quick compiler: fix for missing defs
When the verifier replaces a Dex instruction, it may cause us
to lose a definition, making the SSA graph invalid. This CL
deals with this situation by introducing dummy definitions.
With this CL, run-tests 042 and 075 pass. The only remaining
run-test failures are related to missing exception edges in the CFG.
The old compiler could infer some of them, while llvm requires all
to be explicit.
Change-Id: I471fa515d8717aa102713a05b0e4115bf656b78e
diff --git a/src/compiler/CompilerIR.h b/src/compiler/CompilerIR.h
index 7420bda..1ecf61a 100644
--- a/src/compiler/CompilerIR.h
+++ b/src/compiler/CompilerIR.h
@@ -420,6 +420,7 @@
irb(NULL),
placeholderBB(NULL),
entryBB(NULL),
+ entryTargetBB(NULL),
tempName(0),
requireShadowFrame(false),
numShadowFrameEntries(0),
@@ -589,6 +590,7 @@
greenland::IRBuilder* irb;
llvm::BasicBlock* placeholderBB;
llvm::BasicBlock* entryBB;
+ llvm::BasicBlock* entryTargetBB;
std::string bitcode_filename;
GrowableList llvmValues;
int32_t tempName;
diff --git a/src/compiler/codegen/MethodBitcode.cc b/src/compiler/codegen/MethodBitcode.cc
index 3eb6a89..83ebf9b 100644
--- a/src/compiler/codegen/MethodBitcode.cc
+++ b/src/compiler/codegen/MethodBitcode.cc
@@ -53,6 +53,9 @@
placeholder->replaceAllUsesWith(val);
val->takeName(placeholder);
cUnit->llvmValues.elemList[sReg] = (intptr_t)val;
+ llvm::Instruction* inst = llvm::dyn_cast<llvm::Instruction>(placeholder);
+ DCHECK(inst != NULL);
+ inst->eraseFromParent();
}
llvm::Type* llvmTypeFromLocRec(CompilationUnit* cUnit, RegLocation loc)
@@ -334,7 +337,6 @@
args.push_back(cUnit->irb->getInt32(info1));
args.push_back(cUnit->irb->getInt32(info2));
cUnit->irb->CreateCall(func, args);
- cUnit->irb->CreateUnreachable();
}
void emitSuspendCheck(CompilationUnit* cUnit)
@@ -1755,7 +1757,9 @@
}
}
- if ((bb->fallThrough != NULL) && !bb->hasReturn) {
+ if (bb->blockType == kEntryBlock) {
+ cUnit->entryTargetBB = getLLVMBlock(cUnit, bb->fallThrough->id);
+ } else if ((bb->fallThrough != NULL) && !bb->hasReturn) {
cUnit->irb->CreateBr(getLLVMBlock(cUnit, bb->fallThrough->id));
}
@@ -1891,16 +1895,13 @@
arg_iter++; /* Skip path method */
for (int i = 0; i < cUnit->numSSARegs; i++) {
llvm::Value* val;
- llvm::Type* ty = llvmTypeFromLocRec(cUnit, cUnit->regLocation[i]);
- if (i < cUnit->numRegs) {
- // Skip non-argument _0 names - should never be a use
- oatInsertGrowableList(cUnit, &cUnit->llvmValues, (intptr_t)0);
- } else if (i >= (cUnit->numRegs + cUnit->numIns)) {
+ if ((i < cUnit->numRegs) || (i >= (cUnit->numRegs + cUnit->numIns))) {
// Handle SSA defs, skipping Method* and compiler temps
if (SRegToVReg(cUnit, i) < 0) {
val = NULL;
} else {
- val = cUnit->irb->CreateLoad(cUnit->irb->CreateAlloca(ty, 0));
+ llvm::Constant* immValue = cUnit->irb->GetJInt(0);
+ val = emitConst(cUnit, immValue, cUnit->regLocation[i]);
val->setName(llvmSSAName(cUnit, i));
}
oatInsertGrowableList(cUnit, &cUnit->llvmValues, (intptr_t)val);
@@ -1920,12 +1921,43 @@
}
}
}
- cUnit->irb->CreateBr(cUnit->placeholderBB);
oatDataFlowAnalysisDispatcher(cUnit, methodBlockBitcodeConversion,
kPreOrderDFSTraversal, false /* Iterative */);
- cUnit->placeholderBB->eraseFromParent();
+ /*
+ * In a few rare cases of verification failure, the verifier will
+ * replace one or more Dalvik opcodes with the special
+ * throw-verification-failure opcode. This can leave the SSA graph
+ * in an invalid state, as definitions may be lost, while uses retained.
+ * To work around this problem, we insert placeholder definitions for
+ * all Dalvik SSA regs in the "placeholder" block. Here, after
+ * bitcode conversion is complete, we examine those placeholder definitions
+ * and delete any with no references (which normally is all of them).
+ *
+ * If any definitions remain, we link the placeholder block into the
+ * CFG. Otherwise, it is deleted.
+ */
+ for (llvm::BasicBlock::iterator it = cUnit->placeholderBB->begin(),
+ itEnd = cUnit->placeholderBB->end(); it != itEnd;) {
+ llvm::Instruction* inst = llvm::dyn_cast<llvm::Instruction>(it++);
+ DCHECK(inst != NULL);
+ llvm::Value* val = llvm::dyn_cast<llvm::Value>(inst);
+ DCHECK(val != NULL);
+ if (val->getNumUses() == 0) {
+ inst->eraseFromParent();
+ }
+ }
+ setDexOffset(cUnit, 0);
+ if (cUnit->placeholderBB->empty()) {
+ cUnit->placeholderBB->eraseFromParent();
+ } else {
+ cUnit->irb->SetInsertPoint(cUnit->placeholderBB);
+ cUnit->irb->CreateBr(cUnit->entryTargetBB);
+ cUnit->entryTargetBB = cUnit->placeholderBB;
+ }
+ cUnit->irb->SetInsertPoint(cUnit->entryBB);
+ cUnit->irb->CreateBr(cUnit->entryTargetBB);
llvm::verifyFunction(*cUnit->func, llvm::PrintMessageAction);
