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..382f90d8d8b5d00b48e270b16d8731281fa87d4b 100644
--- a/runtime/vm/intrinsifier_arm64.cc
+++ b/runtime/vm/intrinsifier_arm64.cc
@@ -33,9 +33,18 @@ intptr_t Intrinsifier::ParameterSlotFromSp() { return -1; }
 
 
 void Intrinsifier::IntrinsicCallPrologue(Assembler* assembler) {
+  COMPILE_ASSERT((1 << CODE_REG) & kAbiPreservedCpuRegs);
+  COMPILE_ASSERT(((1 << ARGS_DESC_REG) & kAbiPreservedCpuRegs) == 0);
+  COMPILE_ASSERT((1 << CALLEE_SAVED_TEMP) & kAbiPreservedCpuRegs);
+  COMPILE_ASSERT((1 << CALLEE_SAVED_TEMP2) & kAbiPreservedCpuRegs);
+  COMPILE_ASSERT(CALLEE_SAVED_TEMP != CODE_REG);
+  COMPILE_ASSERT(CALLEE_SAVED_TEMP != ARGS_DESC_REG);
+  COMPILE_ASSERT(CALLEE_SAVED_TEMP2 != CODE_REG);
+  COMPILE_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);
 }