Subzero: Validate phi instructions after CFG construction.
It checks that each phi label corresponds to an incoming edge, and that each incoming edge has a corresponding phi label.
It does not check that duplicate incoming edges get the same phi value.
Performance impact is minimal (~0.2%) despite the O(N^2) implementation.
BUG= https://code.google.com/p/nativeclient/issues/detail?id=4304
R=jpp@chromium.org
Review URL: https://codereview.chromium.org/1351433002 .
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 57f216f..ed60abb 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -232,6 +232,10 @@
}
}
Nodes.resize(Dest);
+
+ TimerMarker T(TimerStack::TT_phiValidation, this);
+ for (CfgNode *Node : Nodes)
+ Node->validatePhis();
}
void Cfg::renumberInstructions() {
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index cb8d97e..0ccc6ea 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -80,6 +80,46 @@
OutEdges = Insts.rbegin()->getTerminatorEdges();
}
+// Validate each Phi instruction in the node with respect to control flow. For
+// every phi argument, its label must appear in the predecessor list. For each
+// predecessor, there must be a phi argument with that label. We don't check
+// that phi arguments with the same label have the same value.
+void CfgNode::validatePhis() {
+ for (Inst &Instr : Phis) {
+ auto *Phi = llvm::cast<InstPhi>(&Instr);
+ // We do a simple O(N^2) algorithm to check for consistency. Even so, it
+ // shows up as only about 0.2% of the total translation time. But if
+ // necessary, we could improve the complexity by using a hash table to count
+ // how many times each node is referenced in the Phi instruction, and how
+ // many times each node is referenced in the incoming edge list, and compare
+ // the two for equality.
+ for (SizeT i = 0; i < Phi->getSrcSize(); ++i) {
+ CfgNode *Label = Phi->getLabel(i);
+ bool Found = false;
+ for (CfgNode *InNode : getInEdges()) {
+ if (InNode == Label) {
+ Found = true;
+ break;
+ }
+ }
+ if (!Found)
+ llvm::report_fatal_error("Phi error: label for bad incoming edge");
+ }
+ for (CfgNode *InNode : getInEdges()) {
+ bool Found = false;
+ for (SizeT i = 0; i < Phi->getSrcSize(); ++i) {
+ CfgNode *Label = Phi->getLabel(i);
+ if (InNode == Label) {
+ Found = true;
+ break;
+ }
+ }
+ if (!Found)
+ llvm::report_fatal_error("Phi error: missing label for incoming edge");
+ }
+ }
+}
+
// This does part 1 of Phi lowering, by creating a new dest variable
// for each Phi instruction, replacing the Phi instruction's dest with
// that variable, and adding an explicit assignment of the old dest to
diff --git a/src/IceCfgNode.h b/src/IceCfgNode.h
index 63f2c62..a4744db 100644
--- a/src/IceCfgNode.h
+++ b/src/IceCfgNode.h
@@ -90,6 +90,7 @@
CfgNode *splitIncomingEdge(CfgNode *Pred, SizeT InEdgeIndex);
/// @}
+ void validatePhis();
void placePhiLoads();
void placePhiStores();
void deletePhis();
diff --git a/src/IceTimerTree.def b/src/IceTimerTree.def
index 9bcc53c..6db9fbc 100644
--- a/src/IceTimerTree.def
+++ b/src/IceTimerTree.def
@@ -46,6 +46,7 @@
X(parseModule) \
X(parseModuleValuesymtabs) \
X(parseTypes) \
+ X(phiValidation) \
X(placePhiLoads) \
X(placePhiStores) \
X(regAlloc) \
diff --git a/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc b/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc
new file mode 100644
index 0000000..bb9d59e
--- /dev/null
+++ b/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc
@@ -0,0 +1,55 @@
+65535,8,2;
+1,1;
+65535,17,2;
+1,5;
+7,32;
+2;
+7,1;
+21,0,1;
+21,0,1,0;
+65534;
+8,3,0,0,0;
+8,4,0,0,0;
+65535,19,2;
+5,0;
+65534;
+65535,14,2;
+1,0,76,111,111,112,67,97,114,114,105,101,100,68,101,112;
+1,1,66,97,99,107,66,114,97,110,99,104;
+65534;
+65535,12,2;
+1,2;
+65535,11,2;
+1,0;
+4,2;
+4,4;
+65534;
+2,2,1,0;
+11,1;
+43,6,0;
+16,0,2,0,3,0;
+2,1,4,0;
+11,1;
+65534;
+65535,12,2;
+1,7;
+65535,11,2;
+1,2;
+4,3;
+65534;
+11,4;
+43,7,0;
+2,2,4294967293,0;
+11,6;
+43,8,0;
+2,3,4294967293,0;
+11,6;
+2,4,4294967295,0;
+11,6;
+2,5,5,0;
+11,1,5,5;
+2,1,6,0;
+11,2,3,6;
+10;
+65534;
+65534;
diff --git a/tests_lit/llvm2ice_tests/phi_invalid.test b/tests_lit/llvm2ice_tests/phi_invalid.test
new file mode 100644
index 0000000..198de4c
--- /dev/null
+++ b/tests_lit/llvm2ice_tests/phi_invalid.test
@@ -0,0 +1,7 @@
+; Test that a bad phi instruction is caught.
+; https://code.google.com/p/nativeclient/issues/detail?id=4304
+
+RUN: %p2i --expect-fail --tbc -i %p/Input/phi-invalid.tbc --insts 2>&1 \
+RUN: | FileCheck --check-prefix=BADPHI %s
+
+; BADPHI: Phi error:
