yaxunl created this revision.
yaxunl added reviewers: tra, rsmith, MaskRay, rtrieu.
Herald added a project: All.
yaxunl requested review of this revision.
Currently clang emits warning with -Wconversion for the following code:
long foo(long x) {
return 1LL<<x;
}
warning: implicit conversion changes signedness: 'long long' to 'long'
[-Wsign-conversion]
return 1ll << x;
~~~~~~ ~~~~^~~~
This does not make sense since all operands are signed.
https://reviews.llvm.org/D144011
Files:
clang/lib/Sema/SemaChecking.cpp
clang/test/Sema/sign-conversion.c
Index: clang/test/Sema/sign-conversion.c
===================================================================
--- clang/test/Sema/sign-conversion.c
+++ clang/test/Sema/sign-conversion.c
@@ -5,4 +5,8 @@
void test(int x) {
unsigned t0 = x; // expected-warning {{implicit conversion changes
signedness}}
unsigned t1 = (t0 == 5 ? x : 0); // expected-warning {{operand of ? changes
signedness}}
+
+ // Clang has special treatment for left shift of literal '1'.
+ // Make sure there is no diagnostics.
+ long t2 = 1LL << x;
}
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -14281,6 +14281,11 @@
}
}
+ if (SourceBT && SourceBT->isInteger() && TargetBT &&
+ TargetBT->isInteger()) {
+ return;
+ }
+
// Fall through for non-constants to give a sign conversion warning.
}
Index: clang/test/Sema/sign-conversion.c
===================================================================
--- clang/test/Sema/sign-conversion.c
+++ clang/test/Sema/sign-conversion.c
@@ -5,4 +5,8 @@
void test(int x) {
unsigned t0 = x; // expected-warning {{implicit conversion changes signedness}}
unsigned t1 = (t0 == 5 ? x : 0); // expected-warning {{operand of ? changes signedness}}
+
+ // Clang has special treatment for left shift of literal '1'.
+ // Make sure there is no diagnostics.
+ long t2 = 1LL << x;
}
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -14281,6 +14281,11 @@
}
}
+ if (SourceBT && SourceBT->isInteger() && TargetBT &&
+ TargetBT->isInteger()) {
+ return;
+ }
+
// Fall through for non-constants to give a sign conversion warning.
}
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