Fix compile-time regression caused by rL371928

Summary:
Also fixup rL371928 for cases that occur on our out-of-tree backend

There were still quite a few intermediate APInts and this caused the
compile time of MCCodeEmitter for our target to jump from 16s up to
~5m40s. This patch, brings it back down to ~17s by eliminating pretty
much all of them using two new APInt functions (extractBitsAsZExtValue(),
insertBits() but with a uint64_t). The exact conditions for eliminating
them is that the field extracted/inserted must be <=64-bit which is
almost always true.

Note: The two new APInt API's assume that APInt::WordSize is at least
64-bit because that means they touch at most 2 APInt words. They
statically assert that's true. It seems very unlikely that someone
is patching it to be smaller so this should be fine.

Reviewers: jmolloy

Reviewed By: jmolloy

Subscribers: hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67686

llvm-svn: 372243

5 files changed, 183 insertions, 43 deletions

diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 987ca636cef..8dce5a621bb 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -1503,9 +1503,11 @@ public:
 
   /// Insert the bits from a smaller APInt starting at bitPosition.
   void insertBits(const APInt &SubBits, unsigned bitPosition);
+  void insertBits(uint64_t SubBits, unsigned bitPosition, unsigned numBits);
 
   /// Return an APInt with the extracted bits [bitPosition,bitPosition+numBits).
   APInt extractBits(unsigned numBits, unsigned bitPosition) const;
+  uint64_t extractBitsAsZExtValue(unsigned numBits, unsigned bitPosition) const;
 
   /// @}
   /// \name Value Characterization Functions
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index 43173311cd8..758fe8b4f86 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -401,6 +401,33 @@ void APInt::insertBits(const APInt &subBits, unsigned bitPosition) {
   }
 }
 
+void APInt::insertBits(uint64_t subBits, unsigned bitPosition, unsigned numBits) {
+  uint64_t maskBits = maskTrailingOnes<uint64_t>(numBits);
+  subBits &= maskBits;
+  if (isSingleWord()) {
+    U.VAL &= ~(maskBits << bitPosition);
+    U.VAL |= subBits << bitPosition;
+    return;
+  }
+
+  unsigned loBit = whichBit(bitPosition);
+  unsigned loWord = whichWord(bitPosition);
+  unsigned hiWord = whichWord(bitPosition + numBits - 1);
+  if (loWord == hiWord) {
+    U.pVal[loWord] &= ~(maskBits << loBit);
+    U.pVal[loWord] |= subBits << loBit;
+    return;
+  }
+
+  static_assert(8 * sizeof(WordType) <= 64, "This code assumes only two words affected");
+  unsigned wordBits = 8 * sizeof(WordType);
+  U.pVal[loWord] &= ~(maskBits << loBit);
+  U.pVal[loWord] |= subBits << loBit;
+
+  U.pVal[hiWord] &= ~(maskBits >> (wordBits - loBit));
+  U.pVal[hiWord] |= subBits >> (wordBits - loBit);
+}
+
 APInt APInt::extractBits(unsigned numBits, unsigned bitPosition) const {
   assert(numBits > 0 && "Can't extract zero bits");
   assert(bitPosition < BitWidth && (numBits + bitPosition) <= BitWidth &&
@@ -438,6 +465,31 @@ APInt APInt::extractBits(unsigned numBits, unsigned bitPosition) const {
   return Result.clearUnusedBits();
 }
 
+uint64_t APInt::extractBitsAsZExtValue(unsigned numBits,
+                                       unsigned bitPosition) const {
+  assert(numBits > 0 && "Can't extract zero bits");
+  assert(bitPosition < BitWidth && (numBits + bitPosition) <= BitWidth &&
+         "Illegal bit extraction");
+  assert(numBits <= 64 && "Illegal bit extraction");
+
+  uint64_t maskBits = maskTrailingOnes<uint64_t>(numBits);
+  if (isSingleWord())
+    return (U.VAL >> bitPosition) & maskBits;
+
+  unsigned loBit = whichBit(bitPosition);
+  unsigned loWord = whichWord(bitPosition);
+  unsigned hiWord = whichWord(bitPosition + numBits - 1);
+  if (loWord == hiWord)
+    return (U.pVal[loWord] >> loBit) & maskBits;
+
+  static_assert(8 * sizeof(WordType) <= 64, "This code assumes only two words affected");
+  unsigned wordBits = 8 * sizeof(WordType);
+  uint64_t retBits = U.pVal[loWord] >> loBit;
+  retBits |= U.pVal[hiWord] << (wordBits - loBit);
+  retBits &= maskBits;
+  return retBits;
+}
+
 unsigned APInt::getBitsNeeded(StringRef str, uint8_t radix) {
   assert(!str.empty() && "Invalid string length");
   assert((radix == 10 || radix == 8 || radix == 16 || radix == 2 ||
diff --git a/llvm/test/TableGen/BigEncoder.td b/llvm/test/TableGen/BigEncoder.td
index 56689afb152..5c4bc016e26 100644
--- a/llvm/test/TableGen/BigEncoder.td
+++ b/llvm/test/TableGen/BigEncoder.td
@@ -46,21 +46,12 @@ def biz : Instruction {
     }
 
 }
-
 // CHECK-LABEL: case ::biz: {
-// CHECK: const APInt [[x:M[0-9]+]] = APInt::getBitsSet(65, 3, 7);
-// CHECK-NEXT: Value |= (op & [[x]]) << 9;
-// CHECK-NEXT: const APInt [[y:M[0-9]+]] = APInt::getBitsSet(65, 7, 11);
-// CHECK-NEXT: Value |= (op & [[y]]) << 1;
+// CHECK:      Value.insertBits(op.extractBitsAsZExtValue(4, 3), 12, 4);
+// CHECK-NEXT: Value.insertBits(op.extractBitsAsZExtValue(4, 7), 8, 4);
 
 // CHECK-LABEL: case ::foo: {
-// CHECK: const APInt [[x:M[0-9]+]] = APInt::getBitsSet(65, 0, 7);
-// CHECK-NEXT: op &= [[x]];
-// CHECK-NEXT: op <<= 8;
-// CHECK-NEXT: Value |= op;
+// CHECK:      Value.insertBits(op.extractBitsAsZExtValue(7, 0), 8, 7);
 
 // CHECK-LABEL: case ::bar: {
-// CHECK: const APInt [[x:M[0-9]+]] = APInt::getBitsSet(65, 3, 11);
-// CHECK-NEXT: op &= [[x]];
-// CHECK-NEXT: op <<= 5;
-// CHECK-NEXT: Value |= op;
+// CHECK:      Value.insertBits(op.extractBitsAsZExtValue(8, 3), 8, 8);
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index ce511ce06f3..a58d31439e7 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1858,6 +1858,64 @@ TEST(APIntTest, insertBits) {
   EXPECT_EQ(i260.extractBits(4, 256).getZExtValue(), 0x000000000000000Full);
 }
 
+TEST(APIntTest, insertBitsUInt64) {
+  // Tests cloned from insertBits but adapted to the numBits <= 64 constraint
+  uint64_t iSrc = 0x00123456;
+
+  // Direct copy.
+  APInt i31(31, 0x76543210ull);
+  i31.insertBits(iSrc, 0, 31);
+  EXPECT_EQ(static_cast<int64_t>(0x00123456ull), i31.getSExtValue());
+
+  // Single word src/dst insertion.
+  APInt i63(63, 0x01234567FFFFFFFFull);
+  i63.insertBits(iSrc, 4, 31);
+  EXPECT_EQ(static_cast<int64_t>(0x012345600123456Full), i63.getSExtValue());
+
+  // Insert single word src into one word of dst.
+  APInt i120(120, UINT64_MAX, true);
+  i120.insertBits(iSrc, 8, 31);
+  EXPECT_EQ(static_cast<int64_t>(0xFFFFFF80123456FFull), i120.getSExtValue());
+
+  // Insert single word src into two words of dst.
+  APInt i127(127, UINT64_MAX, true);
+  i127.insertBits(iSrc, 48, 31);
+  EXPECT_EQ(i127.extractBits(64, 0).getZExtValue(), 0x3456FFFFFFFFFFFFull);
+  EXPECT_EQ(i127.extractBits(63, 64).getZExtValue(), 0x7FFFFFFFFFFF8012ull);
+
+  // Insert on word boundaries.
+  APInt i128(128, 0);
+  i128.insertBits(UINT64_MAX, 0, 64);
+  i128.insertBits(UINT64_MAX, 64, 64);
+  EXPECT_EQ(-1, i128.getSExtValue());
+
+  APInt i256(256, UINT64_MAX, true);
+  i256.insertBits(0, 0, 64);
+  i256.insertBits(0, 64, 1);
+  i256.insertBits(0, 64, 64);
+  i256.insertBits(0, 128, 5);
+  i256.insertBits(0, 128, 64);
+  i256.insertBits(0, 192, 64);
+  EXPECT_EQ(0u, i256.getSExtValue());
+
+  APInt i257(257, 0);
+  i257.insertBits(APInt(96, UINT64_MAX, true), 64);
+  EXPECT_EQ(i257.extractBitsAsZExtValue(64, 0), 0x0000000000000000ull);
+  EXPECT_EQ(i257.extractBitsAsZExtValue(64, 64), 0xFFFFFFFFFFFFFFFFull);
+  EXPECT_EQ(i257.extractBitsAsZExtValue(64, 128), 0x00000000FFFFFFFFull);
+  EXPECT_EQ(i257.extractBitsAsZExtValue(64, 192), 0x0000000000000000ull);
+  EXPECT_EQ(i257.extractBitsAsZExtValue(1, 256), 0x0000000000000000ull);
+
+  // General insertion.
+  APInt i260(260, UINT64_MAX, true);
+  i260.insertBits(APInt(129, 1ull << 48), 15);
+  EXPECT_EQ(i260.extractBitsAsZExtValue(64, 0), 0x8000000000007FFFull);
+  EXPECT_EQ(i260.extractBitsAsZExtValue(64, 64), 0x0000000000000000ull);
+  EXPECT_EQ(i260.extractBitsAsZExtValue(64, 128), 0xFFFFFFFFFFFF0000ull);
+  EXPECT_EQ(i260.extractBitsAsZExtValue(64, 192), 0xFFFFFFFFFFFFFFFFull);
+  EXPECT_EQ(i260.extractBitsAsZExtValue(4, 256), 0x000000000000000Full);
+}
+
 TEST(APIntTest, extractBits) {
   APInt i32(32, 0x1234567);
   EXPECT_EQ(0x3456, i32.extractBits(16, 4));
@@ -1881,6 +1939,33 @@ TEST(APIntTest, extractBits) {
             APInt(144, "281474976710655", 10).extractBits(48, 1));
 }
 
+TEST(APIntTest, extractBitsAsZExtValue) {
+  // Tests based on extractBits
+  APInt i32(32, 0x1234567);
+  EXPECT_EQ(0x3456u, i32.extractBitsAsZExtValue(16, 4));
+
+  APInt i257(257, 0xFFFFFFFFFF0000FFull, true);
+  EXPECT_EQ(0xFFu, i257.extractBitsAsZExtValue(16, 0));
+  EXPECT_EQ((0xFFu >> 1), i257.extractBitsAsZExtValue(16, 1));
+  EXPECT_EQ(0xFFFFFFFFull, i257.extractBitsAsZExtValue(32, 64));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFull, i257.extractBitsAsZExtValue(64, 128));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFull, i257.extractBitsAsZExtValue(64, 192));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFull, i257.extractBitsAsZExtValue(64, 191));
+  EXPECT_EQ(0x3u, i257.extractBitsAsZExtValue(2, 255));
+  EXPECT_EQ(0xFFFFFFFFFF80007Full, i257.extractBitsAsZExtValue(64, 1));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFull, i257.extractBitsAsZExtValue(64, 65));
+  EXPECT_EQ(0xFFFFFFFFFF80007Full, i257.extractBitsAsZExtValue(64, 1));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFull, i257.extractBitsAsZExtValue(64, 65));
+  EXPECT_EQ(0x1ull, i257.extractBitsAsZExtValue(1, 129));
+
+  EXPECT_EQ(APInt(48, 0),
+            APInt(144, "281474976710655", 10).extractBitsAsZExtValue(48, 48));
+  EXPECT_EQ(APInt(48, 0x0000ffffffffffffull),
+            APInt(144, "281474976710655", 10).extractBitsAsZExtValue(48, 0));
+  EXPECT_EQ(APInt(48, 0x00007fffffffffffull),
+            APInt(144, "281474976710655", 10).extractBitsAsZExtValue(48, 1));
+}
+
 TEST(APIntTest, getLowBitsSet) {
   APInt i128lo64 = APInt::getLowBitsSet(128, 64);
   EXPECT_EQ(0u, i128lo64.countLeadingOnes());
diff --git a/llvm/utils/TableGen/CodeEmitterGen.cpp b/llvm/utils/TableGen/CodeEmitterGen.cpp
index 907fa1e8463..10c42bbc6ff 100644
--- a/llvm/utils/TableGen/CodeEmitterGen.cpp
+++ b/llvm/utils/TableGen/CodeEmitterGen.cpp
@@ -212,40 +212,47 @@ AddCodeToMergeInOperand(Record *R, BitsInit *BI, const std::string &VarName,
     std::string maskStr;
     int opShift;
 
+    unsigned loBit = beginVarBit - N + 1;
+    unsigned hiBit = loBit + N;
+    unsigned loInstBit = beginInstBit - N + 1;
     if (UseAPInt) {
-      unsigned loBit = beginVarBit - N + 1;
-      unsigned hiBit = loBit + N;
-      maskStr = "M" + itostr(bit);
-      Case += "      const APInt " + maskStr + " = APInt::getBitsSet(" +
-              itostr(BitWidth) + ", " + itostr(loBit) + ", " + itostr(hiBit) +
-              ");\n";
+      std::string extractStr;
+      if (N >= 64) {
+        extractStr = "op.extractBits(" + itostr(hiBit - loBit) + ", " +
+                     itostr(loBit) + ")";
+        Case += "      Value.insertBits(" + extractStr + ", " +
+                itostr(loInstBit) + ");\n";
+      } else {
+        extractStr = "op.extractBitsAsZExtValue(" + itostr(hiBit - loBit) +
+                     ", " + itostr(loBit) + ")";
+        Case += "      Value.insertBits(" + extractStr + ", " +
+                itostr(loInstBit) + ", " + itostr(hiBit - loBit) + ");\n";
+      }
     } else {
       uint64_t opMask = ~(uint64_t)0 >> (64 - N);
       opShift = beginVarBit - N + 1;
       opMask <<= opShift;
       maskStr = "UINT64_C(" + utostr(opMask) + ")";
-    }
-    opShift = beginInstBit - beginVarBit;
-
-    if (numOperandLits == 1) {
-      // Because Op may be an APInt, ensure all arithmetic is done in-place
-      // where possible to elide copies.
-      Case += "      op &= " + maskStr + ";\n";
-      if (opShift > 0) {
-        Case += "      op <<= " + itostr(opShift) + ";\n";
-      } else if (opShift < 0) {
-        Case += "      op >>= " + itostr(-opShift) + ";\n";
-      }
-      Case += "      Value |= op;\n";
-    } else {
-      if (opShift > 0) {
-        Case += "      Value |= (op & " + maskStr + ") << " + itostr(opShift) +
-                ";\n";
-      } else if (opShift < 0) {
-        Case += "      Value |= (op & " + maskStr + ") >> " + itostr(-opShift) +
-                ";\n";
+      opShift = beginInstBit - beginVarBit;
+
+      if (numOperandLits == 1) {
+        Case += "      op &= " + maskStr + ";\n";
+        if (opShift > 0) {
+          Case += "      op <<= " + itostr(opShift) + ";\n";
+        } else if (opShift < 0) {
+          Case += "      op >>= " + itostr(-opShift) + ";\n";
+        }
+        Case += "      Value |= op;\n";
       } else {
-        Case += "      Value |= (op & " + maskStr + ");\n";
+        if (opShift > 0) {
+          Case += "      Value |= (op & " + maskStr + ") << " +
+                  itostr(opShift) + ";\n";
+        } else if (opShift < 0) {
+          Case += "      Value |= (op & " + maskStr + ") >> " +
+                  itostr(-opShift) + ";\n";
+        } else {
+          Case += "      Value |= (op & " + maskStr + ");\n";
+        }
       }
     }
   }
@@ -436,9 +443,12 @@ void CodeEmitterGen::run(raw_ostream &o) {
     << "    raw_string_ostream Msg(msg);\n"
     << "    Msg << \"Not supported instr: \" << MI;\n"
     << "    report_fatal_error(Msg.str());\n"
-    << "  }\n"
-    << "  return Value;\n"
-    << "}\n\n";
+    << "  }\n";
+  if (UseAPInt)
+    o << "  Inst = Value;\n";
+  else
+    o << "  return Value;\n";
+  o << "}\n\n";
 
   const auto &All = SubtargetFeatureInfo::getAll(Records);
   std::map<Record *, SubtargetFeatureInfo, LessRecordByID> SubtargetFeatures;