bitops: fix rol/ror when shift is zero

All the variants for rol/ror have a bug in case where the shift == 0.
For example rol32, would generate:

    return (word << 0) | (word >> 32);

Which though works, would be flagged as a runtime error on clang's
sanitizer.

Suggested-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 98fb005aba393bfc91abf50144cc8e96a4ad86a8..1881284cb5f3434306e79a0eadc69392c1020f9d 100644 (file)
--- a/include/qemu/bitops.h
+++ b/include/qemu/bitops.h
@@ -218,7 +218,7 @@ static inline unsigned long hweight_long(unsigned long w)
  */
 static inline uint8_t rol8(uint8_t word, unsigned int shift)
 {
-    return (word << shift) | (word >> (8 - shift));
+    return (word << shift) | (word >> ((8 - shift) & 7));
 }
 
 /**
@@ -228,7 +228,7 @@ static inline uint8_t rol8(uint8_t word, unsigned int shift)
  */
 static inline uint8_t ror8(uint8_t word, unsigned int shift)
 {
-    return (word >> shift) | (word << (8 - shift));
+    return (word >> shift) | (word << ((8 - shift) & 7));
 }
 
 /**
@@ -238,7 +238,7 @@ static inline uint8_t ror8(uint8_t word, unsigned int shift)
  */
 static inline uint16_t rol16(uint16_t word, unsigned int shift)
 {
-    return (word << shift) | (word >> (16 - shift));
+    return (word << shift) | (word >> ((16 - shift) & 15));
 }
 
 /**
@@ -248,7 +248,7 @@ static inline uint16_t rol16(uint16_t word, unsigned int shift)
  */
 static inline uint16_t ror16(uint16_t word, unsigned int shift)
 {
-    return (word >> shift) | (word << (16 - shift));
+    return (word >> shift) | (word << ((16 - shift) & 15));
 }
 
 /**
@@ -258,7 +258,7 @@ static inline uint16_t ror16(uint16_t word, unsigned int shift)
  */
 static inline uint32_t rol32(uint32_t word, unsigned int shift)
 {
-    return (word << shift) | (word >> (32 - shift));
+    return (word << shift) | (word >> ((32 - shift) & 31));
 }
 
 /**
@@ -268,7 +268,7 @@ static inline uint32_t rol32(uint32_t word, unsigned int shift)
  */
 static inline uint32_t ror32(uint32_t word, unsigned int shift)
 {
-    return (word >> shift) | (word << (32 - shift));
+    return (word >> shift) | (word << ((32 - shift) & 31));
 }
 
 /**
@@ -278,7 +278,7 @@ static inline uint32_t ror32(uint32_t word, unsigned int shift)
  */
 static inline uint64_t rol64(uint64_t word, unsigned int shift)
 {
-    return (word << shift) | (word >> (64 - shift));
+    return (word << shift) | (word >> ((64 - shift) & 63));
 }
 
 /**
@@ -288,7 +288,7 @@ static inline uint64_t rol64(uint64_t word, unsigned int shift)
  */
 static inline uint64_t ror64(uint64_t word, unsigned int shift)
 {
-    return (word >> shift) | (word << (64 - shift));
+    return (word >> shift) | (word << ((64 - shift) & 63));
 }
 
 /**