-fcatch-undefined-behavior: add the -ftrapv checks to the set of things caught

by this mode, and also check for signed left shift overflow. The rules for the
latter are a little subtle:

 * neither C89 nor C++98 specify the behavior of a signed left shift at all
 * in C99 and C11, shifting a 1 bit into the sign bit has undefined behavior
 * in C++11, with core issue 1457, shifting a 1 bit *out* of the sign bit has
   undefined behavior

As of this change, we use the C99 rules for all C language variants, and the
C++11 rules for all C++ language variants. Once we have individual
-fcatch-undefined-behavior= flags, this should be revisited.

llvm-svn: 162634

1 files changed, 25 insertions, 0 deletions

diff --git a/clang/test/CodeGen/catch-undef-behavior.c b/clang/test/CodeGen/catch-undef-behavior.c
index 8c45fa50456..5832b6c830f 100644
--- a/clang/test/CodeGen/catch-undef-behavior.c
+++ b/clang/test/CodeGen/catch-undef-behavior.c
@@ -19,3 +19,28 @@ int bar(int *a) {
   // CHECK-NEXT: icmp eq i64 %[[MISALIGN]], 0
   return *a;
 }
+
+// CHECK: @lsh_overflow
+int lsh_overflow(int a, int b) {
+  // CHECK: %[[INBOUNDS:.*]] = icmp ule i32 %[[RHS:.*]], 31
+  // CHECK-NEXT: br i1 %[[INBOUNDS]]
+
+  // CHECK: %[[SHIFTED_OUT_WIDTH:.*]] = sub nuw nsw i32 31, %[[RHS]]
+  // CHECK-NEXT: %[[SHIFTED_OUT:.*]] = lshr i32 %[[LHS:.*]], %[[SHIFTED_OUT_WIDTH]]
+  // CHECK-NEXT: %[[NO_OVERFLOW:.*]] = icmp eq i32 %[[SHIFTED_OUT]], 0
+  // CHECK-NEXT: br i1 %[[NO_OVERFLOW]]
+
+  // CHECK: %[[RET:.*]] = shl i32 %[[LHS]], %[[RHS]]
+  // CHECK-NEXT: ret i32 %[[RET]]
+  return a << b;
+}
+
+// CHECK: @rsh_inbounds
+int rsh_inbounds(int a, int b) {
+  // CHECK: %[[INBOUNDS:.*]] = icmp ult i32 %[[RHS:.*]], 32
+  // CHECK: br i1 %[[INBOUNDS]]
+
+  // CHECK: %[[RET:.*]] = ashr i32 %[[LHS]], %[[RHS]]
+  // CHECK-NEXT: ret i32 %[[RET]]
+  return a >> b;
+}