Don't compile methods with irreducible loops and String.<init>.

The current code doesn't work when dex register aliases.

bug: 78493232
Test: m
Change-Id: I1c296f6dc914388844ae5eb7d84f3bd7d81e1f87

2 files changed, 9 insertions, 2 deletions

diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index 9647dd5d41..a36e80379d 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -1360,9 +1360,15 @@ bool HInstructionBuilder::HandleStringInit(HInvoke* invoke,
   if (arg_this->IsNewInstance()) {
     ssa_builder_->AddUninitializedString(arg_this->AsNewInstance());
   } else {
+    // The only reason a HPhi can flow in a String.<init> is when there is an
+    // irreducible loop, which will create HPhi for all dex registers at loop entry.
     DCHECK(arg_this->IsPhi());
-    // NewInstance is not the direct input of the StringFactory call. It might
-    // be redundant but optimizing this case is not worth the effort.
+    DCHECK(graph_->HasIrreducibleLoops());
+    // Don't bother compiling a method in that situation. While we could look at all
+    // phis related to the HNewInstance, it's not worth the trouble.
+    MaybeRecordStat(compilation_stats_,
+                    MethodCompilationStat::kNotCompiledIrreducibleAndStringInit);
+    return false;
   }
 
   // Walk over all vregs and replace any occurrence of `arg_this` with `invoke`.
diff --git a/compiler/optimizing/optimizing_compiler_stats.h b/compiler/optimizing/optimizing_compiler_stats.h
index 9a26f2f6c4..f246228074 100644
--- a/compiler/optimizing/optimizing_compiler_stats.h
+++ b/compiler/optimizing/optimizing_compiler_stats.h
@@ -50,6 +50,7 @@ enum class MethodCompilationStat {
   kNotCompiledThrowCatchLoop,
   kNotCompiledAmbiguousArrayOp,
   kNotCompiledHugeMethod,
+  kNotCompiledIrreducibleAndStringInit,
   kNotCompiledLargeMethodNoBranches,
   kNotCompiledMalformedOpcode,
   kNotCompiledNoCodegen,