What does the cannot load from non-primitive location error mean?

Question

assembler

I wrote the following code
#include
char string1 ="A";
chari;
char j = 0;
// Enable USCI_A0 TX interrupt
int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P1DIR = 0xFF; // All P1.x outputs
P1OUT = 0; // All P1.x reset
P2DIR = 0xFF; // All P2.x outputs
P2OUT = 0; // All P2.x reset
P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
P1SEL2 = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
P3DIR = 0xFF; // All P3.x outputs
P3OUT = 0; // All P3.x reset
UCA0CTL1 |= UCSSEL_1; // CLK = ACLK
UCA0BR0 = 0x03; // 32kHz/9600 = 3.41
UCA0BR1 = 0x00; //
UCA0MCTL = UCBRS1 + UCBRS0; // Modulation UCBRSx = 3
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
IE2 |= UCA0TXIE; // Enable USCI_A0 TX interrupt
UCA0TXBUF = string1;
__bis_SR_register(LPM3_bits + GIE); // Enter LPM3, interrupts enabled
}
// USCI A0/B0 Transmit ISR
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCIAB0TX_VECTOR
__interrupt void USCI0TX_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCIAB0TX_VECTOR))) USCI0TX_ISR (void)
#else
#error Compiler not supported!
#endif
{
UCA0TXBUF = string1; // TX next character
//if (i == sizeof string1) // TX over?
IE2 &= ~UCA0TXIE; // Disable USCI_A0 TX interrupt
}
// USCI A0/B0 Receive ISR
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCIAB0RX_VECTOR))) USCI0RX_ISR (void)
#else
#error Compiler not supported!
#endif
{
char res = UCA0RXBUF;
//if (j > sizeof string1 - 1)
//{
//i = 0;
//j = 0;
//IE2 |= UCA0TXIE; // Enable USCI_A0 TX interrupt
//UCA0TXBUF = string1[i++];
//}
}
Receive buffer cannot load from non-primitive location error