LowerTypeTests: Represent the memory region size with the constant size-1.

This means that we can use a shorter instruction sequence in the case where
the size is a power of two and on the boundary between two representations.

Differential Revision: https://reviews.llvm.org/D28421

llvm-svn: 291706

1 files changed, 15 insertions, 15 deletions

diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index 4ffec0cce53..deb7e819480 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -270,12 +270,12 @@ class LowerTypeTestsModule {
     /// relative to the start address.
     Constant *AlignLog2;
 
-    /// ByteArray, Inline, AllOnes: size of the memory region covering members
-    /// of this type identifier as a multiple of 2^AlignLog2.
-    Constant *Size;
+    /// ByteArray, Inline, AllOnes: one less than the size of the memory region
+    /// covering members of this type identifier as a multiple of 2^AlignLog2.
+    Constant *SizeM1;
 
-    /// ByteArray, Inline, AllOnes: range of the size expressed as a bit width.
-    unsigned SizeBitWidth;
+    /// ByteArray, Inline, AllOnes: range of SizeM1 expressed as a bit width.
+    unsigned SizeM1BitWidth;
 
     /// ByteArray: the byte array to test the address against.
     Constant *TheByteArray;
@@ -593,8 +593,8 @@ Value *LowerTypeTestsModule::lowerTypeTestCall(Metadata *TypeId, CallInst *CI,
                      IntPtrTy));
   Value *BitOffset = B.CreateOr(OffsetSHR, OffsetSHL);
 
-  Constant *BitSizeConst = ConstantExpr::getZExt(TIL.Size, IntPtrTy);
-  Value *OffsetInRange = B.CreateICmpULT(BitOffset, BitSizeConst);
+  Constant *BitSizeConst = ConstantExpr::getZExt(TIL.SizeM1, IntPtrTy);
+  Value *OffsetInRange = B.CreateICmpULE(BitOffset, BitSizeConst);
 
   // If the bit set is all ones, testing against it is unnecessary.
   if (TIL.TheKind == TypeTestResolution::AllOnes)
@@ -711,13 +711,13 @@ void LowerTypeTestsModule::lowerTypeTestCalls(
     if (BSI.isAllOnes()) {
       TIL.TheKind = (BSI.BitSize == 1) ? TypeTestResolution::Single
                                        : TypeTestResolution::AllOnes;
-      TIL.SizeBitWidth = (BSI.BitSize < 256) ? 8 : 32;
-      TIL.Size =
-          ConstantInt::get((BSI.BitSize < 256) ? Int8Ty : Int32Ty, BSI.BitSize);
+      TIL.SizeM1BitWidth = (BSI.BitSize <= 128) ? 7 : 32;
+      TIL.SizeM1 = ConstantInt::get((BSI.BitSize <= 128) ? Int8Ty : Int32Ty,
+                                    BSI.BitSize - 1);
     } else if (BSI.BitSize <= 64) {
       TIL.TheKind = TypeTestResolution::Inline;
-      TIL.SizeBitWidth = (BSI.BitSize <= 32) ? 5 : 6;
-      TIL.Size = ConstantInt::get(Int8Ty, BSI.BitSize);
+      TIL.SizeM1BitWidth = (BSI.BitSize <= 32) ? 5 : 6;
+      TIL.SizeM1 = ConstantInt::get(Int8Ty, BSI.BitSize - 1);
       uint64_t InlineBits = 0;
       for (auto Bit : BSI.Bits)
         InlineBits |= uint64_t(1) << Bit;
@@ -728,9 +728,9 @@ void LowerTypeTestsModule::lowerTypeTestCalls(
             (BSI.BitSize <= 32) ? Int32Ty : Int64Ty, InlineBits);
     } else {
       TIL.TheKind = TypeTestResolution::ByteArray;
-      TIL.SizeBitWidth = (BSI.BitSize < 256) ? 8 : 32;
-      TIL.Size =
-          ConstantInt::get((BSI.BitSize < 256) ? Int8Ty : Int32Ty, BSI.BitSize);
+      TIL.SizeM1BitWidth = (BSI.BitSize <= 128) ? 7 : 32;
+      TIL.SizeM1 = ConstantInt::get((BSI.BitSize <= 128) ? Int8Ty : Int32Ty,
+                                    BSI.BitSize - 1);
       ++NumByteArraysCreated;
       ByteArrayInfo *BAI = createByteArray(BSI);
       TIL.TheByteArray = BAI->ByteArray;