From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 29 May 2008 10:58:49 +0000 (+0000)
Subject: Always use packed structs.  This isn't really very nice, but there's
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0408f6805c164f317937e97d7bc222781164bfeb;p=clang

Always use packed structs.  This isn't really very nice, but there's
nothing fundamentally wrong with it. Emitting unpacked structs where
possible is more work for almost no practical benefit.  We'll probably
want to fix it at some point anyway, but it's low priority.

The issue with long double in particular is that LLVM thinks an X86 long
double is 10 bytes, while clang considers it for all purposes to be
either 12 or 16 bytes, depending on the platform, even in a packed
struct.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@51673 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CodeGenTypes.cpp b/lib/CodeGen/CodeGenTypes.cpp
index 5efde77a7d..ec4f6df2b4 100644
--- a/lib/CodeGen/CodeGenTypes.cpp
+++ b/lib/CodeGen/CodeGenTypes.cpp
@@ -482,14 +482,13 @@ void RecordOrganizer::layoutStructFields(const ASTRecordLayout &RL) {
   // FIXME : Use SmallVector
   uint64_t llvmSize = 0;
   std::vector<const llvm::Type*> LLVMFields;
-  bool packedStruct = false;
   int NumMembers = RD.getNumMembers();
 
   for (int curField = 0; curField < NumMembers; curField++) {
     const FieldDecl *FD = RD.getMember(curField);
     uint64_t offset = RL.getFieldOffset(curField);
     const llvm::Type *Ty = CGT.ConvertTypeRecursive(FD->getType());
-    uint64_t size = CGT.getTargetData().getABITypeSize(Ty) * 8;
+    uint64_t size = CGT.getTargetData().getTypeStoreSizeInBits(Ty);
 
     if (FD->isBitField()) {
       Expr *BitWidth = FD->getBitWidth();
@@ -513,12 +512,6 @@ void RecordOrganizer::layoutStructFields(const ASTRecordLayout &RL) {
         llvmSize += 8;
       }
 
-      unsigned Align = CGT.getTargetData().getABITypeAlignment(Ty) * 8;
-      if (llvmSize % Align)
-        packedStruct = true;
-      else if (offset == 0 && RL.getAlignment() % Align)
-        packedStruct = true;
-
       llvmSize += size;
       CGT.addFieldInfo(FD, LLVMFields.size());
       LLVMFields.push_back(Ty);
@@ -530,7 +523,7 @@ void RecordOrganizer::layoutStructFields(const ASTRecordLayout &RL) {
     llvmSize += 8;
   }
 
-  STy = llvm::StructType::get(LLVMFields, packedStruct);
+  STy = llvm::StructType::get(LLVMFields, true);
   assert(CGT.getTargetData().getABITypeSizeInBits(STy) == RL.getSize());
 }
 
diff --git a/test/CodeGen/struct-x86-darwin.c b/test/CodeGen/struct-x86-darwin.c
index 3d3729dc9b..68e6d72961 100644
--- a/test/CodeGen/struct-x86-darwin.c
+++ b/test/CodeGen/struct-x86-darwin.c
@@ -1,16 +1,14 @@
-// RUN: clang < %s -emit-llvm > %t1
-// Run  grep "STest1 = type { i32, \[4 x i16\], double }" %t1 &&
-// RUN: grep "STest2 = type { i16, i16, i32, i32 }" %t1 &&
-// RUN: grep "STest3 = type { i8, i8, i16, i32 }" %t1 &&
-// RUN: grep "STestB1 = type { i8, i8 }" %t1 &&
-// RUN: grep "STestB2 = type { i8, i8, i8 }" %t1 &&
-// RUN: grep "STestB3 = type { i8, i8 }" %t1 &&
-// RUN: grep "STestB4 = type { i8, i8, i8, i8 }" %t1
-// RUN: grep "STestB5 = type { i8, i8, i8, i8, i8, i8 }" %t1
-// RUN: grep "STestB6 = type { i8, i8, i8, i8 }" %t1
+// RUN: clang < %s -emit-llvm > %t1 -triple=i686-apple-darwin9
+// Run  grep "STest1 = type <{ i32, \[4 x i16\], double }>" %t1 &&
+// RUN: grep "STest2 = type <{ i16, i16, i32, i32 }>" %t1 &&
+// RUN: grep "STest3 = type <{ i8, i8, i16, i32 }>" %t1 &&
+// RUN: grep "STestB1 = type <{ i8, i8 }>" %t1 &&
+// RUN: grep "STestB2 = type <{ i8, i8, i8 }>" %t1 &&
+// RUN: grep "STestB3 = type <{ i8, i8 }>" %t1 &&
+// RUN: grep "STestB4 = type <{ i8, i8, i8, i8 }>" %t1
+// RUN: grep "STestB5 = type <{ i8, i8, i8, i8, i8, i8 }>" %t1
+// RUN: grep "STestB6 = type <{ i8, i8, i8, i8 }>" %t1
 // Test struct layout for x86-darwin target
-// FIXME : Enable this test for x86-darwin only. At the moment clang hard codes
-// x86-darwin as the target
 
 struct STest1 {int x; short y[4]; double z; } st1;
 struct STest2 {short a,b; int c,d; } st2;
diff --git a/test/CodeGen/struct.c b/test/CodeGen/struct.c
index f17a7af76c..f567a0b2ff 100644
--- a/test/CodeGen/struct.c
+++ b/test/CodeGen/struct.c
@@ -163,3 +163,6 @@ int f14(int i, ...) {
 
 /* Attribute packed */
 struct __attribute__((packed)) S2839 { double a[19];  signed char b; } s2839[5];
+
+struct __attribute__((packed)) SS { long double a; char b; } SS;
+