target/arm: Implement XPSR GE bits

In the M-profile architecture, if the CPU implements the DSP extension
then the XPSR has GE bits, in the same way as the A-profile CPSR. When
we added DSP extension support we forgot to add support for reading
and writing the GE bits, which are stored in env->GE. We did put in
the code to add XPSR_GE to the mask of bits to update in the v7m_msr
helper, but forgot it in v7m_mrs. We also must not allow the XPSR we
pull off the stack on exception return to set the nonexistent GE bits.
Correct these errors:
 * read and write env->GE in xpsr_read() and xpsr_write()
 * only set GE bits on exception return if DSP present
 * read GE bits for MRS if DSP present

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190430131439.25251-5-peter.maydell@linaro.org

1 files changed, 4 insertions, 0 deletions

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 0304ddd9f1..733b840a71 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1285,6 +1285,7 @@ static inline uint32_t xpsr_read(CPUARMState *env)
         | (env->CF << 29) | ((env->VF & 0x80000000) >> 3) | (env->QF << 27)
         | (env->thumb << 24) | ((env->condexec_bits & 3) << 25)
         | ((env->condexec_bits & 0xfc) << 8)
+        | (env->GE << 16)
         | env->v7m.exception;
 }
 
@@ -1300,6 +1301,9 @@ static inline void xpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
     if (mask & XPSR_Q) {
         env->QF = ((val & XPSR_Q) != 0);
     }
+    if (mask & XPSR_GE) {
+        env->GE = (val & XPSR_GE) >> 16;
+    }
     if (mask & XPSR_T) {
         env->thumb = ((val & XPSR_T) != 0);
     }