Notify the linker when a TU compiled with split-stack has a function without a prologue.

More context here: https://go-review.googlesource.com/c/go/+/148819/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347614 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMFrameLowering.cpp b/lib/Target/ARM/ARMFrameLowering.cpp
index 3e057e9..d1e4bce 100644 (file)
--- a/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/lib/Target/ARM/ARMFrameLowering.cpp
@@ -2157,9 +2157,15 @@ void ARMFrameLowering::adjustForSegmentedStacks(
 
   // Do not generate a prologue for leaf functions with a stack of size zero.
   // For non-leaf functions we have to allow for the possibility that the
-  // call is to a non-split function, as in PR37807.
-  if (StackSize == 0 && !MFI.hasTailCall())
+  // callis to a non-split function, as in PR37807. This function could also
+  // take the address of a non-split function. When the linker tries to adjust
+  // its non-existent prologue, it would fail with an error. Mark the object
+  // file so that such failures are not errors. See this Go language bug-report
+  // https://go-review.googlesource.com/c/go/+/148819/
+  if (StackSize == 0 && !MFI.hasTailCall()) {
+    MF.getMMI().setHasNosplitStack(true);
     return;
+  }
 
   // Use R4 and R5 as scratch registers.
   // We save R4 and R5 before use and restore them before leaving the function.

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index e40b0f8..d722c75 100644 (file)
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -2270,9 +2270,15 @@ void X86FrameLowering::adjustForSegmentedStacks(
 
   // Do not generate a prologue for leaf functions with a stack of size zero.
   // For non-leaf functions we have to allow for the possibility that the
-  // call is to a non-split function, as in PR37807.
-  if (StackSize == 0 && !MFI.hasTailCall())
+  // callis to a non-split function, as in PR37807. This function could also
+  // take the address of a non-split function. When the linker tries to adjust
+  // its non-existent prologue, it would fail with an error. Mark the object
+  // file so that such failures are not errors. See this Go language bug-report
+  // https://go-review.googlesource.com/c/go/+/148819/
+  if (StackSize == 0 && !MFI.hasTailCall()) {
+    MF.getMMI().setHasNosplitStack(true);
     return;
+  }
 
   MachineBasicBlock *allocMBB = MF.CreateMachineBasicBlock();
   MachineBasicBlock *checkMBB = MF.CreateMachineBasicBlock();

diff --git a/test/CodeGen/X86/segmented-stacks-standalone.ll b/test/CodeGen/X86/segmented-stacks-standalone.ll
new file mode 100644 (file)
index 0000000..a7205e6
--- /dev/null
+++ b/test/CodeGen/X86/segmented-stacks-standalone.ll
@@ -0,0 +1,30 @@
+; RUN: llc < %s -mcpu=generic -mtriple=i686-linux -verify-machineinstrs | FileCheck %s -check-prefix=X32-Linux
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux  -verify-machineinstrs | FileCheck %s -check-prefix=X64-Linux
+
+; This test is standalone because segmented-stacks.ll generates
+; object-files with both .note.GNU-split-stack (for the split-stack
+; functions) and .note.GNU-no-split-stack sections (for the
+; non-split-stack functions). But a split-stack function without a
+; stack frame should have a .note.GNU-split-stack section regardless
+; of any other contents of the compilation unit.
+
+define void @test_nostack() #0 {
+       ret void
+}
+
+attributes #0 = { "split-stack" }
+
+; X32-Linux: .section ".note.GNU-split-stack","",@progbits
+; X32-Linux: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-Linux: .section ".note.GNU-split-stack","",@progbits
+; X64-Linux: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-FreeBSD: .section ".note.GNU-split-stack","",@progbits
+; X64-FreeBSD: .section ".note.GNU-no-split-stack","",@progbits
+
+; X32-DFlyBSD: .section ".note.GNU-split-stack","",@progbits
+; X32-DFlyBSD: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-DFlyBSD: .section ".note.GNU-split-stack","",@progbits
+; X64-DFlyBSD: .section ".note.GNU-no-split-stack","",@progbits