Merge "ARM: Use r4 for stack overflow check to reduce code size."

1 files changed, 6 insertions, 2 deletions

diff --git a/compiler/optimizing/code_generator_arm_vixl.cc b/compiler/optimizing/code_generator_arm_vixl.cc
index 84ba178f7b..504c6479cc 100644
--- a/compiler/optimizing/code_generator_arm_vixl.cc
+++ b/compiler/optimizing/code_generator_arm_vixl.cc
@@ -2490,8 +2490,12 @@ void CodeGeneratorARMVIXL::GenerateFrameEntry() {
   }
 
   if (!skip_overflow_check) {
-    UseScratchRegisterScope temps(GetVIXLAssembler());
-    vixl32::Register temp = temps.Acquire();
+    // Using r4 instead of IP saves 2 bytes. Start by asserting that r4 is available here.
+    for (vixl32::Register reg : kParameterCoreRegistersVIXL) {
+      DCHECK(!reg.Is(r4));
+    }
+    DCHECK(!kCoreCalleeSaves.Includes(r4));
+    vixl32::Register temp = r4;
     __ Sub(temp, sp, Operand::From(GetStackOverflowReservedBytes(InstructionSet::kArm)));
     // The load must immediately precede RecordPcInfo.
     ExactAssemblyScope aas(GetVIXLAssembler(),