wxiao3 created this revision.
wxiao3 added reviewers: annita.zhang, LuoYuanke, smaslov, hjl.tools, RKSimon,
rnk, andreadb.
wxiao3 added a project: clang.
Herald added a subscriber: cfe-commits.
According to i386 System V ABI 2.1: Structures and unions assume the alignment
of their most strictly aligned component. But current implementation always
takes them as 4-byte aligned which will result in incorrect code, e.g:
1 #include <immintrin.h>
2 typedef union {
3 int d[4];
4 __m128 m;
5 } M128;
6 extern void foo(int, ...);
7 void test(void)
8 {
9 M128 a;
10 foo(1, a);
11 foo(1, a.m);
12 }
The first call (line 10) takes the second arg as 4-byte aligned while the
second call (line 11) takes the second arg as 16-byte aligned. There is
oxymoron for the alignment of the 2 calls because they should be the same.
This patch fixes the bug by following i386 System V ABI.
Repository:
rC Clang
https://reviews.llvm.org/D60748
Files:
lib/CodeGen/TargetInfo.cpp
test/CodeGen/x86_32-align-linux.c
test/CodeGen/x86_32-arguments-linux.c
Index: test/CodeGen/x86_32-arguments-linux.c
===================================================================
--- test/CodeGen/x86_32-arguments-linux.c
+++ test/CodeGen/x86_32-arguments-linux.c
@@ -3,21 +3,21 @@
// CHECK-LABEL: define void @f56(
// CHECK: i8 signext %a0, %struct.s56_0* byval align 4 %a1,
-// CHECK: i64 %a2.coerce, %struct.s56_1* byval align 4,
-// CHECK: <1 x double> %a4, %struct.s56_2* byval align 4,
-// CHECK: <4 x i32> %a6, %struct.s56_3* byval align 4,
-// CHECK: <2 x double> %a8, %struct.s56_4* byval align 4,
-// CHECK: <8 x i32> %a10, %struct.s56_5* byval align 4,
-// CHECK: <4 x double> %a12, %struct.s56_6* byval align 4)
+// CHECK: i64 %a2.coerce, %struct.s56_1* byval align 8 %a3,
+// CHECK: <1 x double> %a4, %struct.s56_2* byval align 8 %a5,
+// CHECK: <4 x i32> %a6, %struct.s56_3* byval align 16 %a7,
+// CHECK: <2 x double> %a8, %struct.s56_4* byval align 16 %a9,
+// CHECK: <8 x i32> %a10, %struct.s56_5* byval align 32 %a11,
+// CHECK: <4 x double> %a12, %struct.s56_6* byval align 32 %a13)
// CHECK: call void (i32, ...) @f56_0(i32 1,
// CHECK: i32 %{{.*}}, %struct.s56_0* byval align 4 %{{[^ ]*}},
-// CHECK: i64 %{{[^ ]*}}, %struct.s56_1* byval align 4 %{{[^ ]*}},
-// CHECK: <1 x double> %{{[^ ]*}}, %struct.s56_2* byval align 4 %{{[^ ]*}},
-// CHECK: <4 x i32> %{{[^ ]*}}, %struct.s56_3* byval align 4 %{{[^ ]*}},
-// CHECK: <2 x double> %{{[^ ]*}}, %struct.s56_4* byval align 4 %{{[^ ]*}},
-// CHECK: <8 x i32> %{{[^ ]*}}, %struct.s56_5* byval align 4 %{{[^ ]*}},
-// CHECK: <4 x double> %{{[^ ]*}}, %struct.s56_6* byval align 4 %{{[^ ]*}})
+// CHECK: i64 %{{[^ ]*}}, %struct.s56_1* byval align 8 %{{[^ ]*}},
+// CHECK: <1 x double> %{{[^ ]*}}, %struct.s56_2* byval align 8 %{{[^ ]*}},
+// CHECK: <4 x i32> %{{[^ ]*}}, %struct.s56_3* byval align 16 %{{[^ ]*}},
+// CHECK: <2 x double> %{{[^ ]*}}, %struct.s56_4* byval align 16 %{{[^ ]*}},
+// CHECK: <8 x i32> %{{[^ ]*}}, %struct.s56_5* byval align 32 %{{[^ ]*}},
+// CHECK: <4 x double> %{{[^ ]*}}, %struct.s56_6* byval align 32 %{{[^ ]*}})
// CHECK: }
//
// <rdar://problem/7964854> [i386] clang misaligns long double in structures
Index: test/CodeGen/x86_32-align-linux.c
===================================================================
--- /dev/null
+++ test/CodeGen/x86_32-align-linux.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -w -fblocks -ffreestanding -triple i386-pc-linux-gnu -emit-llvm -o %t %s
+// RUN: FileCheck < %t %s
+
+#include <immintrin.h>
+
+typedef union {
+ int d[4];
+ __m128 m;
+} M128;
+
+extern void foo(int, ...);
+
+M128 a;
+
+// CHECK-LABEL: define void @test
+// CHECK: entry:
+// CHECK: call void (i32, ...) @foo(i32 1, %union.M128* byval align 16
+// CHECK: call void (i32, ...) @foo(i32 1, <4 x float>
+
+void test(void)
+{
+ foo(1, a);
+ foo(1, a.m);
+}
+
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -1492,18 +1492,18 @@
if (Align <= MinABIStackAlignInBytes)
return 0; // Use default alignment.
- // On non-Darwin, the stack type alignment is always 4.
- if (!IsDarwinVectorABI) {
- // Set explicit alignment, since we may need to realign the top.
+ if (IsDarwinVectorABI) {
+ // On Darwin, if the type contains an SSE vector type, the alignment is 16.
+ if (Align >= 16 && (isSSEVectorType(getContext(), Ty) ||
+ isRecordWithSSEVectorType(getContext(), Ty)))
+ return 16;
+ return MinABIStackAlignInBytes;
+ } else if (IsWin32StructABI) {
return MinABIStackAlignInBytes;
}
-
- // Otherwise, if the type contains an SSE vector type, the alignment is 16.
- if (Align >= 16 && (isSSEVectorType(getContext(), Ty) ||
- isRecordWithSSEVectorType(getContext(), Ty)))
- return 16;
-
- return MinABIStackAlignInBytes;
+ // i386 System V ABI 2.1: Structures and unions assume the alignment of their
+ // most strictly aligned component.
+ return Align;
}
ABIArgInfo X86_32ABIInfo::getIndirectResult(QualType Ty, bool ByVal,
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
