[llvm] r277768 - GlobalISel: refuse to halve size of 1-byte & odd-sized LLTs.

[Tim Northover via llvm-commits]

Author: tnorthover
Date: Thu Aug  4 15:54:05 2016
New Revision: 277768

URL: http://llvm.org/viewvc/llvm-project?rev=277768&view=rev
Log:
GlobalISel: refuse to halve size  of 1-byte & odd-sized LLTs.

Modified:
    llvm/trunk/include/llvm/CodeGen/LowLevelType.h
    llvm/trunk/unittests/CodeGen/LowLevelTypeTest.cpp

Modified: llvm/trunk/include/llvm/CodeGen/LowLevelType.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LowLevelType.h?rev=277768&r1=277767&r2=277768&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/LowLevelType.h (original)
+++ llvm/trunk/include/llvm/CodeGen/LowLevelType.h Thu Aug  4 15:54:05 2016
@@ -131,7 +131,8 @@ public:
   /// size of the scalar type involved. For example `s32` will become `s16`,
   /// `<2 x s32>` will become `<2 x s16>`.
   LLT halfScalarSize() const {
-    assert(isSized() && "cannot change size of this type");
+    assert(isSized() && getScalarSizeInBits() > 1 &&
+           getScalarSizeInBits() % 2 == 0 && "cannot half size of this type");
     return LLT{Kind, NumElements, SizeOrAddrSpace / 2};
   }
 

Modified: llvm/trunk/unittests/CodeGen/LowLevelTypeTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/CodeGen/LowLevelTypeTest.cpp?rev=277768&r1=277767&r2=277768&view=diff
==============================================================================
--- llvm/trunk/unittests/CodeGen/LowLevelTypeTest.cpp (original)
+++ llvm/trunk/unittests/CodeGen/LowLevelTypeTest.cpp Thu Aug  4 15:54:05 2016
@@ -34,7 +34,7 @@ TEST(LowLevelTypeTest, Scalar) {
 
   for (unsigned S : {1U, 17U, 32U, 64U, 0xfffffU}) {
     const LLT Ty = LLT::scalar(S);
-    const LLT HalfTy = Ty.halfScalarSize();
+    const LLT HalfTy = (S % 2) == 0 ? Ty.halfScalarSize() : Ty;
     const LLT DoubleTy = Ty.doubleScalarSize();
 
     // Test kind.
@@ -51,13 +51,14 @@ TEST(LowLevelTypeTest, Scalar) {
     EXPECT_EQ(S, Ty.getSizeInBits());
     EXPECT_EQ(S, Ty.getScalarSizeInBits());
 
-    // Is it OK to half an odd-sized scalar? It currently is.
-    EXPECT_EQ(S/2, HalfTy.getSizeInBits());
-    EXPECT_EQ(S/2, HalfTy.getScalarSizeInBits());
-
     EXPECT_EQ(S*2, DoubleTy.getSizeInBits());
     EXPECT_EQ(S*2, DoubleTy.getScalarSizeInBits());
 
+    if ((S % 2) == 0) {
+      EXPECT_EQ(S/2, HalfTy.getSizeInBits());
+      EXPECT_EQ(S/2, HalfTy.getScalarSizeInBits());
+    }
+
     // Test equality operators.
     EXPECT_TRUE(Ty == Ty);
     EXPECT_FALSE(Ty != Ty);
@@ -87,7 +88,7 @@ TEST(LowLevelTypeTest, Vector) {
       // Test getElementType().
       EXPECT_EQ(STy, VTy.getElementType());
 
-      const LLT HalfSzTy = VTy.halfScalarSize();
+      const LLT HalfSzTy = ((S % 2) == 0) ? VTy.halfScalarSize() : VTy;
       const LLT DoubleSzTy = VTy.doubleScalarSize();
 
       // halfElements requires an even number of elements.
@@ -123,9 +124,11 @@ TEST(LowLevelTypeTest, Vector) {
       EXPECT_EQ(S, VTy.getScalarSizeInBits());
       EXPECT_EQ(Elts, VTy.getNumElements());
 
-      EXPECT_EQ((S / 2) * Elts, HalfSzTy.getSizeInBits());
-      EXPECT_EQ(S / 2, HalfSzTy.getScalarSizeInBits());
-      EXPECT_EQ(Elts, HalfSzTy.getNumElements());
+      if ((S % 2) == 0) {
+        EXPECT_EQ((S / 2) * Elts, HalfSzTy.getSizeInBits());
+        EXPECT_EQ(S / 2, HalfSzTy.getScalarSizeInBits());
+        EXPECT_EQ(Elts, HalfSzTy.getNumElements());
+      }
 
       EXPECT_EQ((S * 2) * Elts, DoubleSzTy.getSizeInBits());
       EXPECT_EQ(S * 2, DoubleSzTy.getScalarSizeInBits());