Block the receiver register always before Android M.
Art before M assumes that the type of the value in the receiver
register never changes. This assumption is used during verification
and therefore allowing reused of the receiver register can make
verification fail on these devices.
R=sgjesse@google.com, zerny@google.com
Bug: 73787793
Change-Id: Icfe9cd87be16d8e8364c319876c0700a3285d5fa
diff --git a/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java b/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
index 24def66..fefe8c5 100644
--- a/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
+++ b/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
@@ -2039,6 +2039,24 @@
private void computeLiveRanges() {
computeLiveRanges(options, code, liveAtEntrySets, liveIntervals);
+ // Art VMs before Android M assume that the register for the receiver never changes its value.
+ // This assumption is used during verification. Allowing the receiver register to be
+ // overwritten can therefore lead to verification errors. If we could be targeting one of these
+ // VMs we block the receiver register throughout the method.
+ if (options.canHaveThisTypeVerifierBug() && !code.method.accessFlags.isStatic()) {
+ for (Instruction instruction : code.blocks.get(0).getInstructions()) {
+ if (instruction.isArgument() && instruction.outValue().isThis()) {
+ Value thisValue = instruction.outValue();
+ LiveIntervals thisIntervals = thisValue.getLiveIntervals();
+ thisIntervals.getRanges().clear();
+ thisIntervals.addRange(new LiveRange(0, code.getNextInstructionNumber()));
+ for (Set<Value> values : liveAtEntrySets.values()) {
+ values.add(thisValue);
+ }
+ return;
+ }
+ }
+ }
}
/**
diff --git a/src/main/java/com/android/tools/r8/utils/InternalOptions.java b/src/main/java/com/android/tools/r8/utils/InternalOptions.java
index 6fc9e17..b486abe 100644
--- a/src/main/java/com/android/tools/r8/utils/InternalOptions.java
+++ b/src/main/java/com/android/tools/r8/utils/InternalOptions.java
@@ -489,4 +489,11 @@
public boolean canUseNotInstruction() {
return minApiLevel >= AndroidApiLevel.L.getLevel();
}
+
+ // Art before M has a verifier bug where the type of the contents of the receiver register is
+ // assumed to not change. If the receiver register is reused for something else the verifier
+ // will fail and the code will not run.
+ public boolean canHaveThisTypeVerifierBug() {
+ return minApiLevel < AndroidApiLevel.M.getLevel();
+ }
}
