[AsmPrinter] Make isRepeatedByteSequence smarter about odd integer types

- zext the value to alloc size first, then check if the value repeats
  with zero padding included. If so we can still emit a .space
- Do the checking with APInt.isSplat(8), which handles non-pow2 types
- Also handle large constants (bit width > 64)
- In a ConstantArray all elements have the same type, so it's sufficient
  to check the first constant recursively and then just compare if all
  following constants are the same by pointer compare

llvm-svn: 239977

1 files changed, 16 insertions, 26 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 3c2f1d9ebcf..bb6bc75b55e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1795,40 +1795,30 @@ static int isRepeatedByteSequence(const ConstantDataSequential *V) {
 /// composed of a repeated sequence of identical bytes and return the
 /// byte value.  If it is not a repeated sequence, return -1.
 static int isRepeatedByteSequence(const Value *V, TargetMachine &TM) {
-
   if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
-    if (CI->getBitWidth() > 64) return -1;
-
-    uint64_t Size =
-        TM.getDataLayout()->getTypeAllocSize(V->getType());
-    uint64_t Value = CI->getZExtValue();
+    uint64_t Size = TM.getDataLayout()->getTypeAllocSizeInBits(V->getType());
+    assert(Size % 8 == 0);
 
-    // Make sure the constant is at least 8 bits long and has a power
-    // of 2 bit width.  This guarantees the constant bit width is
-    // always a multiple of 8 bits, avoiding issues with padding out
-    // to Size and other such corner cases.
-    if (CI->getBitWidth() < 8 || !isPowerOf2_64(CI->getBitWidth())) return -1;
+    // Extend the element to take zero padding into account.
+    APInt Value = CI->getValue().zextOrSelf(Size);
+    if (!Value.isSplat(8))
+      return -1;
 
-    uint8_t Byte = static_cast<uint8_t>(Value);
-
-    for (unsigned i = 1; i < Size; ++i) {
-      Value >>= 8;
-      if (static_cast<uint8_t>(Value) != Byte) return -1;
-    }
-    return Byte;
+    return Value.zextOrTrunc(8).getZExtValue();
   }
   if (const ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
     // Make sure all array elements are sequences of the same repeated
     // byte.
     assert(CA->getNumOperands() != 0 && "Should be a CAZ");
-    int Byte = isRepeatedByteSequence(CA->getOperand(0), TM);
-    if (Byte == -1) return -1;
-
-    for (unsigned i = 1, e = CA->getNumOperands(); i != e; ++i) {
-      int ThisByte = isRepeatedByteSequence(CA->getOperand(i), TM);
-      if (ThisByte == -1) return -1;
-      if (Byte != ThisByte) return -1;
-    }
+    Constant *Op0 = CA->getOperand(0);
+    int Byte = isRepeatedByteSequence(Op0, TM);
+    if (Byte == -1)
+      return -1;
+
+    // All array elements must be equal.
+    for (unsigned i = 1, e = CA->getNumOperands(); i != e; ++i)
+      if (CA->getOperand(i) != Op0)
+        return -1;
     return Byte;
   }