[PATCH] D67573: Fix __atomic_is_lock_free's return type.

[James Y Knight via Phabricator via cfe-commits]

jyknight created this revision.
jyknight added a reviewer: rsmith.
Herald added subscribers: cfe-commits, jfb, kristof.beyls.
Herald added a project: clang.

It is specified to return a bool in GCC's documentation and
implementation, but the clang builtin says it returns an int. This
would be pretty much harmless, if it was just the builtin.

However, when clang translates the builtin into a libcall, it _also_
generates the libcall with an int return type, while the actual
library function in libatomic returns a bool.

This mismatch in return types results in an actual ABI mismatch and
thus incorrect results (interpreting false return value as true) on at
least x86_64.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D67573

Files:
  clang/include/clang/Basic/Builtins.def
  clang/test/CodeGen/atomic-ops.c
  clang/test/CodeGen/big-atomic-ops.c


Index: clang/test/CodeGen/big-atomic-ops.c
===================================================================
--- clang/test/CodeGen/big-atomic-ops.c
+++ clang/test/CodeGen/big-atomic-ops.c
@@ -198,20 +198,20 @@
 int lock_free(struct Incomplete *incomplete) {
   // CHECK: @lock_free
 
-  // CHECK: call i32 @__atomic_is_lock_free(i64 3, i8* null)
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i64 3, i8* null)
   __c11_atomic_is_lock_free(3);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i64 16, i8* {{.*}}@sixteen{{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i64 16, i8* {{.*}}@sixteen{{.*}})
   __atomic_is_lock_free(16, &sixteen);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i64 17, i8* {{.*}}@seventeen{{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i64 17, i8* {{.*}}@seventeen{{.*}})
   __atomic_is_lock_free(17, &seventeen);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i64 4, {{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i64 4, {{.*}})
   __atomic_is_lock_free(4, incomplete);
 
   char cs[20];
-  // CHECK: call i32 @__atomic_is_lock_free(i64 4, {{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i64 4, {{.*}})
   __atomic_is_lock_free(4, cs+1);
 
   // CHECK-NOT: call
Index: clang/test/CodeGen/atomic-ops.c
===================================================================
--- clang/test/CodeGen/atomic-ops.c
+++ clang/test/CodeGen/atomic-ops.c
@@ -343,20 +343,20 @@
 int lock_free(struct Incomplete *incomplete) {
   // CHECK-LABEL: @lock_free
 
-  // CHECK: call i32 @__atomic_is_lock_free(i32 3, i8* null)
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i32 3, i8* null)
   __c11_atomic_is_lock_free(3);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i32 16, i8* {{.*}}@sixteen{{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i32 16, i8* {{.*}}@sixteen{{.*}})
   __atomic_is_lock_free(16, &sixteen);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i32 17, i8* {{.*}}@seventeen{{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i32 17, i8* {{.*}}@seventeen{{.*}})
   __atomic_is_lock_free(17, &seventeen);
 
-  // CHECK: call i32 @__atomic_is_lock_free(i32 4, {{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i32 4, {{.*}})
   __atomic_is_lock_free(4, incomplete);
 
   char cs[20];
-  // CHECK: call i32 @__atomic_is_lock_free(i32 4, {{.*}})
+  // CHECK: call zeroext i1 @__atomic_is_lock_free(i32 4, {{.*}})
   __atomic_is_lock_free(4, cs+1);
 
   // CHECK-NOT: call
Index: clang/include/clang/Basic/Builtins.def
===================================================================
--- clang/include/clang/Basic/Builtins.def
+++ clang/include/clang/Basic/Builtins.def
@@ -720,7 +720,7 @@
 ATOMIC_BUILTIN(__c11_atomic_fetch_xor, "v.", "t")
 BUILTIN(__c11_atomic_thread_fence, "vi", "n")
 BUILTIN(__c11_atomic_signal_fence, "vi", "n")
-BUILTIN(__c11_atomic_is_lock_free, "iz", "n")
+BUILTIN(__c11_atomic_is_lock_free, "bz", "n")
 
 // GNU atomic builtins.
 ATOMIC_BUILTIN(__atomic_load, "v.", "t")
@@ -748,7 +748,7 @@
 BUILTIN(__atomic_thread_fence, "vi", "n")
 BUILTIN(__atomic_signal_fence, "vi", "n")
 BUILTIN(__atomic_always_lock_free, "izvCD*", "n")
-BUILTIN(__atomic_is_lock_free, "izvCD*", "n")
+BUILTIN(__atomic_is_lock_free, "bzvCD*", "n")
 
 // OpenCL 2.0 atomic builtins.
 ATOMIC_BUILTIN(__opencl_atomic_init, "v.", "t")


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