[APInt] Add unittests that demonstrate how very broken APIntOps::isShiftedMask is.
Did you know that 0 is a shifted mask? But 0x0000ff00 and 0x000000ff aren't? At least we get 0xff000000 right.
I only see one usage of this function in the code base today and its in InstCombine. I think its protected against 0 being misreported as a mask. I guess we just don't have tests for the missed cases.
llvm-svn: 299187
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 2148d4f..f05cbb9 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1575,6 +1575,31 @@
}
}
+TEST(APIntTest, isShiftedMask) {
+ EXPECT_FALSE(APIntOps::isShiftedMask(32, APInt(32, 0x01010101)));
+ EXPECT_TRUE(APIntOps::isShiftedMask(32, APInt(32, 0xf0000000)));
+ EXPECT_TRUE(APIntOps::isShiftedMask(32, APInt(32, 0xffff0000)));
+ EXPECT_FALSE(APIntOps::isShiftedMask(32, APInt(32, 0xff << 1))); // BUG
+
+ for (int N : { 1, 2, 3, 4, 7, 8, 16, 32, 64, 127, 128, 129, 256 }) {
+ EXPECT_TRUE(APIntOps::isShiftedMask(N, APInt(N, 0))); // BUG
+
+ APInt One(N, 1);
+ for (int I = 1; I < N; ++I) {
+ APInt MaskVal = One.shl(I) - 1;
+ EXPECT_FALSE(APIntOps::isShiftedMask(N, MaskVal)); // BUG
+ }
+ for (int I = 1; I < N - 1; ++I) {
+ APInt MaskVal = One.shl(I);
+ EXPECT_FALSE(APIntOps::isShiftedMask(N, MaskVal)); // BUG
+ }
+ for (int I = 1; I < N; ++I) {
+ APInt MaskVal = APInt::getHighBitsSet(N, I);
+ EXPECT_TRUE(APIntOps::isShiftedMask(N, MaskVal));
+ }
+ }
+}
+
#if defined(__clang__)
// Disable the pragma warning from versions of Clang without -Wself-move
#pragma clang diagnostic push