ARM/ARM64: Fix smashed CODE_REG in intrinsics with InvokeMathCFunctionInstrs.

runtime/vm/intrinsifier_arm64.cc

Index: runtime/vm/intrinsifier_arm64.cc
diff --git a/runtime/vm/intrinsifier_arm64.cc b/runtime/vm/intrinsifier_arm64.cc
index 0ca8c25fa63444e7ed7c22ef53c10ea12ec625b6..fbaa1677dc0c268fd8c7d4c89f60c0d8fd6e5c76 100644
--- a/runtime/vm/intrinsifier_arm64.cc
+++ b/runtime/vm/intrinsifier_arm64.cc
@@ -32,17 +32,31 @@ namespace dart {
 intptr_t Intrinsifier::ParameterSlotFromSp() { return -1; }
 
 
+static bool IsABIPreservedRegister(Register reg) {
+  return ((1 << reg) & kAbiPreservedCpuRegs) != 0;
+}
+
+
 void Intrinsifier::IntrinsicCallPrologue(Assembler* assembler) {
+  ASSERT(IsABIPreservedRegister(CODE_REG));
+  ASSERT(!IsABIPreservedRegister(ARGS_DESC_REG));
+  ASSERT(IsABIPreservedRegister(CALLEE_SAVED_TEMP));
+  ASSERT(IsABIPreservedRegister(CALLEE_SAVED_TEMP2));
+  ASSERT(CALLEE_SAVED_TEMP != CODE_REG);
+  ASSERT(CALLEE_SAVED_TEMP != ARGS_DESC_REG);
+  ASSERT(CALLEE_SAVED_TEMP2 != CODE_REG);
+  ASSERT(CALLEE_SAVED_TEMP2 != ARGS_DESC_REG);
+
   assembler->Comment("IntrinsicCallPrologue");
   assembler->mov(CALLEE_SAVED_TEMP, LR);
-  assembler->mov(CALLEE_SAVED_TEMP2, R4);
+  assembler->mov(CALLEE_SAVED_TEMP2, ARGS_DESC_REG);
 }
 
 
 void Intrinsifier::IntrinsicCallEpilogue(Assembler* assembler) {
   assembler->Comment("IntrinsicCallEpilogue");
   assembler->mov(LR, CALLEE_SAVED_TEMP);
-  assembler->mov(R4, CALLEE_SAVED_TEMP2);
+  assembler->mov(ARGS_DESC_REG, CALLEE_SAVED_TEMP2);
 }