[PATCH] D17542: Disallow generating vzeroupper before return instruction (iret) in interrupt handler function

[Amjad Aboud via llvm-commits]

aaboud updated this revision to Diff 49374.
aaboud added a comment.

Minor changes to follow Ahmed & David comments.


http://reviews.llvm.org/D17542

Files:
  lib/Target/X86/X86VZeroUpper.cpp
  test/CodeGen/X86/x86-interrupt_vzeroupper.ll

Index: lib/Target/X86/X86VZeroUpper.cpp
===================================================================
--- lib/Target/X86/X86VZeroUpper.cpp
+++ lib/Target/X86/X86VZeroUpper.cpp
@@ -80,6 +80,7 @@
     BlockStateMap BlockStates;
     DirtySuccessorsWorkList DirtySuccessors;
     bool EverMadeChange;
+    bool IsX86INTR;
     const TargetInstrInfo *TII;
 
     static char ID;
@@ -181,10 +182,13 @@
 
   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
     MachineInstr *MI = I;
+    // 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 @@
 
     // 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 @@
   TII = ST.getInstrInfo();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   EverMadeChange = false;
+  IsX86INTR = MF.getFunction()->getCallingConv() == CallingConv::X86_INTR;
 
   bool FnHasLiveInYmm = checkFnHasLiveInYmm(MRI);
 
Index: test/CodeGen/X86/x86-interrupt_vzeroupper.ll
===================================================================
--- test/CodeGen/X86/x86-interrupt_vzeroupper.ll
+++ test/CodeGen/X86/x86-interrupt_vzeroupper.ll
@@ -0,0 +1,41 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown < %s | FileCheck %s
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Checks that interrupt handler code does not call "vzeroupper" instruction
+;; before iret.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Command line: -mavx -S -o - -emit-llvm -O2
+;; Source:
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;extern void foo (void *) __attribute__ ((interrupt));
+;;extern void bar (void);
+;;
+;;void foo (void *frame)
+;;{
+;;  bar ();
+;;}
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+; CHECK: vzeroupper
+; CHECK-NEXT: call
+; CHECK-NOT: vzeroupper
+; CHECK: iret
+
+ at llvm.used = appending global [1 x i8*] [i8* bitcast (void (i8*)* @foo to i8*)], section "llvm.metadata"
+
+; Function Attrs: nounwind
+define x86_intrcc void @foo(i8* nocapture readnone %frame) #0 {
+entry:
+  tail call void @bar() #2
+  ret void
+}
+
+declare void @bar() #1
+
+attributes #0 = { nounwind "disable-tail-calls"="true" "stackrealign" "target-features"="+avx" }
+attributes #1 = { "target-features"="+avx" }
+attributes #2 = { nounwind }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 3.9.0 (trunk 259349) (llvm/trunk 259357)"}


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