Disallow generating vzeroupper before return instruction (iret) in interrupt handler function.

This resolves https://llvm.org/bugs/show_bug.cgi?id=26412

Differential Revision: http://reviews.llvm.org/D17542

llvm-svn: 262319

2 files changed, 27 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86VZeroUpper.cpp b/llvm/lib/Target/X86/X86VZeroUpper.cpp
index cd822b08361..172f8665fad 100644
--- a/llvm/lib/Target/X86/X86VZeroUpper.cpp
+++ b/llvm/lib/Target/X86/X86VZeroUpper.cpp
@@ -80,6 +80,7 @@ namespace {
     BlockStateMap BlockStates;
     DirtySuccessorsWorkList DirtySuccessors;
     bool EverMadeChange;
+    bool IsX86INTR;
     const TargetInstrInfo *TII;
 
     static char ID;
@@ -181,10 +182,13 @@ void VZeroUpperInserter::processBasicBlock(MachineBasicBlock &MBB) {
 
   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
     MachineInstr *MI = I;
-    bool isControlFlow = MI->isCall() || MI->isReturn();
+    // No need for vzeroupper before iret in interrupt handler function,
+    // epilogue will restore YMM registers if needed.
+    bool IsReturnFromX86INTR = IsX86INTR && MI->isReturn();
+    bool IsControlFlow = MI->isCall() || MI->isReturn();
 
     // Shortcut: don't need to check regular instructions in dirty state.
-    if (!isControlFlow && CurState == EXITS_DIRTY)
+    if ((!IsControlFlow || IsReturnFromX86INTR) && CurState == EXITS_DIRTY)
       continue;
 
     if (hasYmmReg(MI)) {
@@ -196,7 +200,7 @@ void VZeroUpperInserter::processBasicBlock(MachineBasicBlock &MBB) {
 
     // Check for control-flow out of the current function (which might
     // indirectly execute SSE instructions).
-    if (!isControlFlow)
+    if (!IsControlFlow || IsReturnFromX86INTR)
       continue;
 
     // If the call won't clobber any YMM register, skip it as well. It usually
@@ -253,6 +257,7 @@ bool VZeroUpperInserter::runOnMachineFunction(MachineFunction &MF) {
   TII = ST.getInstrInfo();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   EverMadeChange = false;
+  IsX86INTR = MF.getFunction()->getCallingConv() == CallingConv::X86_INTR;
 
   bool FnHasLiveInYmm = checkFnHasLiveInYmm(MRI);
 
diff --git a/llvm/test/CodeGen/X86/x86-interrupt_vzeroupper.ll b/llvm/test/CodeGen/X86/x86-interrupt_vzeroupper.ll
new file mode 100644
index 00000000000..ab9f168d972
--- /dev/null
+++ b/llvm/test/CodeGen/X86/x86-interrupt_vzeroupper.ll
@@ -0,0 +1,19 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=+avx < %s | FileCheck %s
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Checks that interrupt handler code does not call "vzeroupper" instruction
+;; before iret.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+; CHECK: vzeroupper
+; CHECK-NEXT: call
+; CHECK-NOT: vzeroupper
+; CHECK: iret
+
+define x86_intrcc void @foo(i8* %frame) {
+  call void @bar()
+  ret void
+}
+
+declare void @bar()
+