This affected code generation of jump tables from switches. This was the
assembly difference for a switch when going from PIC to static:
$ cat t.cpp
void g(int);
void f(int x) {
switch (x) {
case 0: g(0); break;
case 1: g(1); break;
case 2: g(2); break;
case 3: g(3); break;
case 4: g(4); break;
case 5: g(5); break;
case 6: g(6); break;
case 7: g(7); break;
case 8: g(8); break;
case 9: g(9); break;
}
g(10);
}
$ clang -cc1 t.cpp -S -o - -munwind-tables -mrelocation-model pic -o pic.s
$ clang -cc1 t.cpp -S -o - -munwind-tables -mrelocation-model static -o
static.s
$ diff -u pic.s static.s
--- pic.s 2016-12-28 09:32:48.190468800 -0800
+++ static.s 2016-12-28 09:32:53.476899200 -0800
@@ -21,11 +21,9 @@
movq %rax, 40(%rsp)
movq %rdx, 32(%rsp)
ja .LBB0_11
- leaq .LJTI0_0(%rip), %rax
- movq 40(%rsp), %rcx
- movslq (%rax,%rcx,4), %rdx
- addq %rax, %rdx
- jmpq *%rdx
+ movq 40(%rsp), %rax
+ movq .LJTI0_0(,%rax,8), %rcx
+ jmpq *%rcx
.LBB0_1:
xorl %ecx, %ecx
callq "?g@@YAXH@Z"
@@ -71,20 +69,21 @@
nop
addq $56, %rsp
retq
- .p2align 2, 0x90
+ .section .rdata,"dr"
+ .p2align 3
.LJTI0_0:
- .long .LBB0_1-.LJTI0_0
- .long .LBB0_2-.LJTI0_0
- .long .LBB0_3-.LJTI0_0
- .long .LBB0_4-.LJTI0_0
- .long .LBB0_5-.LJTI0_0
- .long .LBB0_6-.LJTI0_0
- .long .LBB0_7-.LJTI0_0
- .long .LBB0_8-.LJTI0_0
- .long .LBB0_9-.LJTI0_0
- .long .LBB0_10-.LJTI0_0
+ .quad .LBB0_1
+ .quad .LBB0_2
+ .quad .LBB0_3
+ .quad .LBB0_4
+ .quad .LBB0_5
+ .quad .LBB0_6
+ .quad .LBB0_7
+ .quad .LBB0_8
+ .quad .LBB0_9
+ .quad .LBB0_10
.seh_handlerdata
- .text
+ .section .rdata,"dr"
.Lcfi3:
.seh_endproc
I think we actually want the .rdata section, but we probably want to use
".long .LBB0_N@IMGREL" jump table entries.
This triggers a latent bug in unwind info emission, because .seh_endproc is
in the wrong section (.rdata, not .text).
Let's revert, fix the latent bug, make switch lowering do what we want, and
then re-land.
On Wed, Dec 28, 2016 at 9:10 AM, Reid Kleckner <r...@google.com> wrote:
> I suspect this broke Win64:
> http://lab.llvm.org:8011/builders/clang-x64-ninja-win7/builds/1410
>
> On Mon, Dec 26, 2016 at 6:20 PM, Saleem Abdulrasool via cfe-commits <
> cfe-commits@lists.llvm.org> wrote:
>
>> Author: compnerd
>> Date: Mon Dec 26 20:20:35 2016
>> New Revision: 290569
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=290569&view=rev
>> Log:
>> Driver: switch Windows to static RelocModel
>>
>> Windows uses PE/COFF which is inherently position independent. The use
>> of the PIC model is unnecessary. In fact, we would generate invalid
>> code using the ELF PIC model when PIC was enabled previously. Now that
>> we no longer accept -fPIC and -fpoc, this switches the internal
>> representation to the static model to permit us to make PIC modules
>> invalid when targeting Windows. This should not change the code
>> generation, only the internal state management.
>>
>> Modified:
>> cfe/trunk/lib/Driver/MSVCToolChain.cpp
>> cfe/trunk/lib/Driver/ToolChains.cpp
>> cfe/trunk/lib/Driver/ToolChains.h
>> cfe/trunk/test/Driver/pic.c
>>
>> Modified: cfe/trunk/lib/Driver/MSVCToolChain.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/MSV
>> CToolChain.cpp?rev=290569&r1=290568&r2=290569&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Driver/MSVCToolChain.cpp (original)
>> +++ cfe/trunk/lib/Driver/MSVCToolChain.cpp Mon Dec 26 20:20:35 2016
>> @@ -82,18 +82,6 @@ bool MSVCToolChain::IsUnwindTablesDefaul
>> return getArch() == llvm::Triple::x86_64;
>> }
>>
>> -bool MSVCToolChain::isPICDefault() const {
>> - return getArch() == llvm::Triple::x86_64;
>> -}
>> -
>> -bool MSVCToolChain::isPIEDefault() const {
>> - return false;
>> -}
>> -
>> -bool MSVCToolChain::isPICDefaultForced() const {
>> - return getArch() == llvm::Triple::x86_64;
>> -}
>> -
>> #ifdef USE_WIN32
>> static bool readFullStringValue(HKEY hkey, const char *valueName,
>> std::string &value) {
>>
>> Modified: cfe/trunk/lib/Driver/ToolChains.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Too
>> lChains.cpp?rev=290569&r1=290568&r2=290569&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Driver/ToolChains.cpp (original)
>> +++ cfe/trunk/lib/Driver/ToolChains.cpp Mon Dec 26 20:20:35 2016
>> @@ -2880,22 +2880,13 @@ bool Generic_GCC::IsUnwindTablesDefault(
>>
>> bool Generic_GCC::isPICDefault() const {
>> switch (getArch()) {
>> - case llvm::Triple::x86_64:
>> - return getTriple().isOSWindows();
>> + default: return false;
>> case llvm::Triple::ppc64:
>> case llvm::Triple::ppc64le:
>> return !getTriple().isOSBinFormatMachO() && !getTriple().isMacOSX();
>> - default:
>> - return false;
>> }
>> }
>>
>> -bool Generic_GCC::isPIEDefault() const { return false; }
>> -
>> -bool Generic_GCC::isPICDefaultForced() const {
>> - return getArch() == llvm::Triple::x86_64 && getTriple().isOSWindows();
>> -}
>> -
>> bool Generic_GCC::IsIntegratedAssemblerDefault() const {
>> switch (getTriple().getArch()) {
>> case llvm::Triple::x86:
>>
>> Modified: cfe/trunk/lib/Driver/ToolChains.h
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Too
>> lChains.h?rev=290569&r1=290568&r2=290569&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Driver/ToolChains.h (original)
>> +++ cfe/trunk/lib/Driver/ToolChains.h Mon Dec 26 20:20:35 2016
>> @@ -232,8 +232,8 @@ public:
>>
>> bool IsUnwindTablesDefault() const override;
>> bool isPICDefault() const override;
>> - bool isPIEDefault() const override;
>> - bool isPICDefaultForced() const override;
>> + bool isPIEDefault() const override { return false; }
>> + bool isPICDefaultForced() const override { return false; }
>> bool IsIntegratedAssemblerDefault() const override;
>> llvm::opt::DerivedArgList *
>> TranslateArgs(const llvm::opt::DerivedArgList &Args, StringRef
>> BoundArch,
>> @@ -1136,9 +1136,9 @@ public:
>>
>> bool IsIntegratedAssemblerDefault() const override;
>> bool IsUnwindTablesDefault() const override;
>> - bool isPICDefault() const override;
>> - bool isPIEDefault() const override;
>> - bool isPICDefaultForced() const override;
>> + bool isPICDefault() const override { return false; }
>> + bool isPIEDefault() const override { return false; }
>> + bool isPICDefaultForced() const override { return false; }
>>
>> void
>> AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
>>
>> Modified: cfe/trunk/test/Driver/pic.c
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/pi
>> c.c?rev=290569&r1=290568&r2=290569&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/test/Driver/pic.c (original)
>> +++ cfe/trunk/test/Driver/pic.c Mon Dec 26 20:20:35 2016
>> @@ -255,9 +255,4 @@
>> // RUN: | FileCheck %s --check-prefix=CHECK-PIC1
>> // RUN: %clang -c %s -target arm64-linux-android -### 2>&1 \
>> // RUN: | FileCheck %s --check-prefix=CHECK-PIC1
>> -//
>> -// On Windows-X64 PIC is enabled by default
>> -// RUN: %clang -c %s -target x86_64-pc-windows-msvc18.0.0 -### 2>&1 \
>> -// RUN: | FileCheck %s --check-prefix=CHECK-PIC2
>> -// RUN: %clang -c %s -target x86_64-pc-windows-gnu -### 2>&1 \
>> -// RUN: | FileCheck %s --check-prefix=CHECK-PIC2
>> +
>>
>>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits@lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>
>
>
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