[APInt] Add saturating truncation methods

Summary:
The signed one is needed for implementation of `ConstantRange::smul_sat()`,
unsigned is for completeness only.

Reviewers: nikic, RKSimon, spatel

Reviewed By: nikic

Subscribers: hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69993

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index fe4e7426099..030b000c258 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1177,9 +1177,26 @@ TEST(APIntTest, fromString) {
 
 TEST(APIntTest, SaturatingMath) {
   APInt AP_10 = APInt(8, 10);
+  APInt AP_42 = APInt(8, 42);
   APInt AP_100 = APInt(8, 100);
   APInt AP_200 = APInt(8, 200);
 
+  EXPECT_EQ(APInt(7, 100), AP_100.truncUSat(7));
+  EXPECT_EQ(APInt(6, 63), AP_100.truncUSat(6));
+  EXPECT_EQ(APInt(5, 31), AP_100.truncUSat(5));
+
+  EXPECT_EQ(APInt(7, 127), AP_200.truncUSat(7));
+  EXPECT_EQ(APInt(6, 63), AP_200.truncUSat(6));
+  EXPECT_EQ(APInt(5, 31), AP_200.truncUSat(5));
+
+  EXPECT_EQ(APInt(7, 42), AP_42.truncSSat(7));
+  EXPECT_EQ(APInt(6, 31), AP_42.truncSSat(6));
+  EXPECT_EQ(APInt(5, 15), AP_42.truncSSat(5));
+
+  EXPECT_EQ(APInt(7, -56), AP_200.truncSSat(7));
+  EXPECT_EQ(APInt(6, -32), AP_200.truncSSat(6));
+  EXPECT_EQ(APInt(5, -16), AP_200.truncSSat(5));
+
   EXPECT_EQ(APInt(8, 200), AP_100.uadd_sat(AP_100));
   EXPECT_EQ(APInt(8, 255), AP_100.uadd_sat(AP_200));
   EXPECT_EQ(APInt(8, 255), APInt(8, 255).uadd_sat(APInt(8, 255)));