[ARM32/Linux] Fix register allocation for null check in call instruction

Fix assertion when two temporary registers are reserved in call instruction

1 files changed, 7 insertions, 2 deletions

diff --git a/src/jit/codegenarm.cpp b/src/jit/codegenarm.cpp
index e276b711c5..b5e3313443 100644
--- a/src/jit/codegenarm.cpp
+++ b/src/jit/codegenarm.cpp
@@ -1952,8 +1952,13 @@ void CodeGen::genCallInstruction(GenTreeCall* call)
     // Insert a null check on "this" pointer if asked.
     if (call->NeedsNullCheck())
     {
-        const regNumber regThis = genGetThisArgReg(call);
-        const regNumber tmpReg  = genRegNumFromMask(call->gtRsvdRegs);
+        const regNumber regThis  = genGetThisArgReg(call);
+        regMaskTP       tempMask = genFindLowestBit(call->gtRsvdRegs);
+        const regNumber tmpReg   = genRegNumFromMask(tempMask);
+        if (genCountBits(call->gtRsvdRegs) > 1)
+        {
+            call->gtRsvdRegs &= ~tempMask;
+        }
         getEmitter()->emitIns_R_R_I(INS_ldr, EA_4BYTE, tmpReg, regThis, 0);
     }