[PATCH] D14609: [ARM,AArch64] Fix __rev16l and __rev16ll intrinsics

[Oliver Stannard via cfe-commits]

olista01 created this revision.
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olista01 set the repository for this revision to rL LLVM.
Herald added subscribers: rengolin, aemerson.

These two intrinsics are defined in arm_acle.h.
    
__rev16l needs to rotate by 16 bits, bit it was actually rotating by 2 bits. For AArch64, where long is 64 bits, this would still be wrong.
    
__rev16ll was incorrect, it reversed the bytes in each 32-bit word, rather than each 16-bit halfword. The correct implementation is to apply __rev16 to the top and bottom words of the 64-bit value.
    
For AArch32 targets, these get compiled down to the hardware rev16 instruction at -O1 and above. For AArch64 targets, the 64-bit ones get compiled to two 32-bit rev16 instructions, because there is not currently a pattern for the 64-bit rev16 instruction.

Repository:
  rL LLVM

http://reviews.llvm.org/D14609

Files:
  lib/Headers/arm_acle.h
  test/CodeGen/arm_acle.c

Index: test/CodeGen/arm_acle.c
===================================================================
--- test/CodeGen/arm_acle.c
+++ test/CodeGen/arm_acle.c
@@ -186,27 +186,53 @@
 
 // ARM-LABEL: test_rev16
 // ARM: llvm.bswap
-// ARM: lshr
-// ARM: shl
+// ARM: lshr {{.*}}, 16
+// ARM: shl {{.*}}, 16
 // ARM: or
 uint32_t test_rev16(uint32_t t) {
   return __rev16(t);
 }
 
 // ARM-LABEL: test_rev16l
-// ARM: llvm.bswap
-// ARM: lshr
-// ARM: shl
-// ARM: or
+// AArch32: llvm.bswap
+// AArch32: lshr {{.*}}, 16
+// AArch32: shl {{.*}}, 16
+// AArch32: or
+// AArch64: [[T1:%.*]] = lshr i64 [[IN:%.*]], 32
+// AArch64: [[T2:%.*]] = trunc i64 [[T1]] to i32
+// AArch64: [[T3:%.*]] = tail call i32 @llvm.bswap.i32(i32 [[T2]])
+// AArch64: [[T4:%.*]] = lshr i32 [[T3]], 16
+// AArch64: [[T5:%.*]] = shl i32 [[T3]], 16
+// AArch64: [[T6:%.*]] = or i32 [[T5]], [[T4]]
+// AArch64: [[T7:%.*]] = zext i32 [[T6]] to i64
+// AArch64: [[T8:%.*]] = shl nuw i64 [[T7]], 32
+// AArch64: [[T9:%.*]] = trunc i64 [[IN]] to i32
+// AArch64: [[T10:%.*]] = tail call i32 @llvm.bswap.i32(i32 [[T9]])
+// AArch64: [[T11:%.*]] = lshr i32 [[T10]], 16
+// AArch64: [[T12:%.*]] = shl i32 [[T10]], 16
+// AArch64: [[T13:%.*]] = or i32 [[T12]], [[T11]]
+// AArch64: [[T14:%.*]] = zext i32 [[T13]] to i64
+// AArch64: [[T15:%.*]] = or i64 [[T8]], [[T14]]
 long test_rev16l(long t) {
   return __rev16l(t);
 }
 
 // ARM-LABEL: test_rev16ll
-// ARM: llvm.bswap
-// ARM: lshr
-// ARM: shl
-// ARM: or
+// ARM: [[T1:%.*]] = lshr i64 [[IN:%.*]], 32
+// ARM: [[T2:%.*]] = trunc i64 [[T1]] to i32
+// ARM: [[T3:%.*]] = tail call i32 @llvm.bswap.i32(i32 [[T2]])
+// ARM: [[T4:%.*]] = lshr i32 [[T3]], 16
+// ARM: [[T5:%.*]] = shl i32 [[T3]], 16
+// ARM: [[T6:%.*]] = or i32 [[T5]], [[T4]]
+// ARM: [[T7:%.*]] = zext i32 [[T6]] to i64
+// ARM: [[T8:%.*]] = shl nuw i64 [[T7]], 32
+// ARM: [[T9:%.*]] = trunc i64 [[IN]] to i32
+// ARM: [[T10:%.*]] = tail call i32 @llvm.bswap.i32(i32 [[T9]])
+// ARM: [[T11:%.*]] = lshr i32 [[T10]], 16
+// ARM: [[T12:%.*]] = shl i32 [[T10]], 16
+// ARM: [[T13:%.*]] = or i32 [[T12]], [[T11]]
+// ARM: [[T14:%.*]] = zext i32 [[T13]] to i64
+// ARM: [[T15:%.*]] = or i64 [[T8]], [[T14]]
 uint64_t test_rev16ll(uint64_t t) {
   return __rev16ll(t);
 }
Index: lib/Headers/arm_acle.h
===================================================================
--- lib/Headers/arm_acle.h
+++ lib/Headers/arm_acle.h
@@ -175,14 +175,18 @@
   return __ror(__rev(t), 16);
 }
 
-static __inline__ unsigned long __attribute__((__always_inline__, __nodebug__))
-  __rev16l(unsigned long t) {
-    return __rorl(__revl(t), sizeof(long) / 2);
-}
-
 static __inline__ uint64_t __attribute__((__always_inline__, __nodebug__))
   __rev16ll(uint64_t t) {
-  return __rorll(__revll(t), 32);
+  return (((uint64_t)__rev16(t >> 32)) << 32) | __rev16(t);
+}
+
+static __inline__ unsigned long __attribute__((__always_inline__, __nodebug__))
+  __rev16l(unsigned long t) {
+#if __SIZEOF_LONG__ == 4
+    return __rev16(t);
+#else
+    return __rev16ll(t);
+#endif
 }
 
 /* REVSH */


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