[Qemu-devel] [PATCH 2/2] target-arm: Avoid "1 << 31" undefined behaviour

[Peter Maydell]

Avoid the undefined behaviour of "1 << 31" by using 1U to make
the shift be of an unsigned value rather than shifting into the
sign bit of a signed integer.

Signed-off-by: Peter Maydell <address@hidden>
---
 target-arm/cpu.h    |    2 +-
 target-arm/helper.c |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index f2abdf3..f3bd501 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -285,7 +285,7 @@ int cpu_arm_handle_mmu_fault (CPUARMState *env, 
target_ulong address, int rw,
 #define CPSR_V (1 << 28)
 #define CPSR_C (1 << 29)
 #define CPSR_Z (1 << 30)
-#define CPSR_N (1 << 31)
+#define CPSR_N (1U << 31)
 #define CPSR_NZCV (CPSR_N | CPSR_Z | CPSR_C | CPSR_V)
 
 #define CPSR_IT (CPSR_IT_0_1 | CPSR_IT_2_7)
diff --git a/target-arm/helper.c b/target-arm/helper.c
index f4e1b06..b13edf1 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -972,7 +972,7 @@ static int par_write(CPUARMState *env, const ARMCPRegInfo 
*ri, uint64_t value)
 static inline bool extended_addresses_enabled(CPUARMState *env)
 {
     return arm_feature(env, ARM_FEATURE_LPAE)
-        && (env->cp15.c2_control & (1 << 31));
+        && (env->cp15.c2_control & (1U << 31));
 }
 
 static int ats_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
@@ -1385,7 +1385,7 @@ static int mpidr_read(CPUARMState *env, const 
ARMCPRegInfo *ri,
      * so these bits always RAZ.
      */
     if (arm_feature(env, ARM_FEATURE_V7MP)) {
-        mpidr |= (1 << 31);
+        mpidr |= (1U << 31);
         /* Cores which are uniprocessor (non-coherent)
          * but still implement the MP extensions set
          * bit 30. (For instance, A9UP.) However we do
-- 
1.7.9.5