Merge remote-tracking branch 'origin/swift-5.1-branch' into stable

Author: swift-ci

lib/CodeGen/CGDecl.cpp

@@ -1788,13 +1788,20 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) {
   if (emission.IsConstantAggregate || D.isConstexpr()) {
     assert(!capturedByInit && "constant init contains a capturing block?");
     constant = ConstantEmitter(*this).tryEmitAbstractForInitializer(D);
-    if (constant && trivialAutoVarInit !=
-                        LangOptions::TrivialAutoVarInitKind::Uninitialized) {
+    if (constant && !constant->isZeroValue() &&
+        (trivialAutoVarInit !=
+         LangOptions::TrivialAutoVarInitKind::Uninitialized)) {
       IsPattern isPattern =
           (trivialAutoVarInit == LangOptions::TrivialAutoVarInitKind::Pattern)
               ? IsPattern::Yes
               : IsPattern::No;
-      constant = constWithPadding(CGM, isPattern,
+      // C guarantees that brace-init with fewer initializers than members in
+      // the aggregate will initialize the rest of the aggregate as-if it were
+      // static initialization. In turn static initialization guarantees that
+      // padding is initialized to zero bits. We could instead pattern-init if D
+      // has any ImplicitValueInitExpr, but that seems to be unintuitive
+      // behavior.
+      constant = constWithPadding(CGM, IsPattern::No,
                                   replaceUndef(CGM, isPattern, constant));
     }
   }

test/CodeGen/padding-init.c

@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -ftrivial-auto-var-init=pattern %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -ftrivial-auto-var-init=zero %s -emit-llvm -o - | FileCheck %s
+
+// C guarantees that brace-init with fewer initializers than members in the
+// aggregate will initialize the rest of the aggregate as-if it were static
+// initialization. In turn static initialization guarantees that padding is
+// initialized to zero bits.
+
+// CHECK: @__const.partial_init.s = private unnamed_addr constant { i8, [7 x i8], i64 } { i8 42, [7 x i8] zeroinitializer, i64 0 }, align 8
+
+// Technically, we could initialize this padding to non-zero because all of the
+// struct's members have initializers.
+
+// CHECK: @__const.init_all.s = private unnamed_addr constant { i8, [7 x i8], i64 } { i8 42, [7 x i8] zeroinitializer, i64 -2401053089374216531 }, align 8
+
+struct S {
+  char c;
+  long long l;
+};
+
+void use(struct S*);
+
+// CHECK-LABEL: @empty_braces(
+// CHECK:       %s = alloca
+// CHECK-NEXT:  %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
+// CHECK-NEXT:  call void @llvm.memset{{.*}}(i8* align 8 %[[B]], i8 0,
+// CHECK-NEXT:  call void @use(%struct.S* %s)
+void empty_braces() {
+  struct S s = {};
+  return use(&s);
+}
+
+// CHECK-LABEL: @partial_init(
+// CHECK:       %s = alloca
+// CHECK-NEXT:  %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
+// CHECK-NEXT:  call void @llvm.memcpy{{.*}}(i8* align 8 %[[B]], {{.*}}@__const.partial_init.s
+// CHECK-NEXT:  call void @use(%struct.S* %s)
+void partial_init() {
+  struct S s = { .c = 42 };
+  return use(&s);
+}
+
+// CHECK-LABEL: @init_all(
+// CHECK:       %s = alloca
+// CHECK-NEXT:  %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
+// CHECK-NEXT:  call void @llvm.memcpy{{.*}}(i8* align 8 %[[B]], {{.*}}@__const.init_all.s
+// CHECK-NEXT:  call void @use(%struct.S* %s)
+void init_all() {
+  struct S s = { .c = 42, .l = 0xdeadbeefc0fedead };
+  return use(&s);
+}

test/CodeGenCXX/auto-var-init.cpp

@@ -64,7 +64,7 @@ struct smallpartinit { char c = 42, d; };
 // PATTERN-O1-NOT: @__const.test_nullinit_custom.custom
 struct nullinit { char* null = nullptr; };
 // PATTERN-O0: @__const.test_padded_uninit.uninit = private unnamed_addr constant { i8, [3 x i8], i32 } { i8 -86, [3 x i8] c"\AA\AA\AA", i32 -1431655766 }, align 4
-// PATTERN-O0: @__const.test_padded_custom.custom = private unnamed_addr constant { i8, [3 x i8], i32 } { i8 42, [3 x i8] c"\AA\AA\AA", i32 13371337 }, align 4
+// PATTERN-O0: @__const.test_padded_custom.custom = private unnamed_addr constant { i8, [3 x i8], i32 } { i8 42, [3 x i8] zeroinitializer, i32 13371337 }, align 4
 // ZERO-O0: @__const.test_padded_custom.custom = private unnamed_addr constant { i8, [3 x i8], i32 } { i8 42, [3 x i8] zeroinitializer, i32 13371337 }, align 4
 // PATTERN-O1-NOT: @__const.test_padded_uninit.uninit
 // PATTERN-O1-NOT: @__const.test_padded_custom.custom
@@ -88,7 +88,7 @@ struct paddedpackedarray { struct paddedpacked p[2]; };
 // PATTERN-O0: @__const.test_unpackedinpacked_uninit.uninit = private unnamed_addr constant <{ { i8, [3 x i8], i32 }, i8 }> <{ { i8, [3 x i8], i32 } { i8 -86, [3 x i8] c"\AA\AA\AA", i32 -1431655766 }, i8 -86 }>, align 1
 struct unpackedinpacked { padded a; char b; } __attribute__((packed));
 // PATTERN-O0: @__const.test_paddednested_uninit.uninit = private unnamed_addr constant { { i8, [3 x i8], i32 }, { i8, [3 x i8], i32 } } { { i8, [3 x i8], i32 } { i8 -86, [3 x i8] c"\AA\AA\AA", i32 -1431655766 }, { i8, [3 x i8], i32 } { i8 -86, [3 x i8] c"\AA\AA\AA", i32 -1431655766 } }, align 4
-// PATTERN: @__const.test_paddednested_custom.custom = private unnamed_addr constant { { i8, [3 x i8], i32 }, { i8, [3 x i8], i32 } } { { i8, [3 x i8], i32 } { i8 42, [3 x i8] c"\AA\AA\AA", i32 13371337 }, { i8, [3 x i8], i32 } { i8 43, [3 x i8] c"\AA\AA\AA", i32 13371338 } }, align 4
+// PATTERN: @__const.test_paddednested_custom.custom = private unnamed_addr constant { { i8, [3 x i8], i32 }, { i8, [3 x i8], i32 } } { { i8, [3 x i8], i32 } { i8 42, [3 x i8] zeroinitializer, i32 13371337 }, { i8, [3 x i8], i32 } { i8 43, [3 x i8] zeroinitializer, i32 13371338 } }, align 4
 // ZERO: @__const.test_paddednested_custom.custom = private unnamed_addr constant { { i8, [3 x i8], i32 }, { i8, [3 x i8], i32 } } { { i8, [3 x i8], i32 } { i8 42, [3 x i8] zeroinitializer, i32 13371337 }, { i8, [3 x i8], i32 } { i8 43, [3 x i8] zeroinitializer, i32 13371338 } }, align 4
 struct paddednested { struct padded p1, p2; };
 // PATTERN-O0: @__const.test_paddedpackednested_uninit.uninit = private unnamed_addr constant %struct.paddedpackednested { %struct.paddedpacked <{ i8 -86, i32 -1431655766 }>, %struct.paddedpacked <{ i8 -86, i32 -1431655766 }> }, align 1
@@ -135,7 +135,7 @@ struct arraytail { int i; int arr[]; };
 // ZERO: @__const.test_intptr4_custom.custom = private unnamed_addr constant [4 x i32*] [i32* inttoptr (i64 572662306 to i32*), i32* inttoptr (i64 572662306 to i32*), i32* inttoptr (i64 572662306 to i32*), i32* inttoptr (i64 572662306 to i32*)], align 16
 // PATTERN-O0: @__const.test_tailpad4_uninit.uninit = private unnamed_addr constant [4 x { i16, i8, [1 x i8] }] [{ i16, i8, [1 x i8] } { i16 -21846, i8 -86, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 -21846, i8 -86, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 -21846, i8 -86, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 -21846, i8 -86, [1 x i8] c"\AA" }], align 16
 // PATTERN-O1-NOT: @__const.test_tailpad4_uninit.uninit
-// PATTERN: @__const.test_tailpad4_custom.custom = private unnamed_addr constant [4 x { i16, i8, [1 x i8] }] [{ i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] c"\AA" }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] c"\AA" }], align 16
+// PATTERN: @__const.test_tailpad4_custom.custom = private unnamed_addr constant [4 x { i16, i8, [1 x i8] }] [{ i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }], align 16
 // ZERO: @__const.test_tailpad4_custom.custom = private unnamed_addr constant [4 x { i16, i8, [1 x i8] }] [{ i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }, { i16, i8, [1 x i8] } { i16 257, i8 1, [1 x i8] zeroinitializer }], align 16
 struct tailpad { short s; char c; };
 // PATTERN-O0: @__const.test_atomicnotlockfree_uninit.uninit = private unnamed_addr constant %struct.notlockfree { [4 x i64] [i64 -6148914691236517206, i64 -6148914691236517206, i64 -6148914691236517206, i64 -6148914691236517206] }, align 8