[X86] MOVPC32r should only emit CFI adjustments when needed

Michael Kuperstein · Michael Kuperstein · commit 53946bf8c68d · 2015-12-15T18:50:32.000Z
We only want to emit CFI adjustments when actually using DWARF. This fixes PR25828. Differential Revision: http://reviews.llvm.org/D15522 llvm-svn: 255664
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1145,11 +1145,12 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
     bool hasFP = FrameLowering->hasFP(*MF);
     
     // TODO: This is needed only if we require precise CFA.
-    bool NeedsDwarfCFI = 
-         (MMI->hasDebugInfo() || MF->getFunction()->needsUnwindTableEntry());
+    bool HasActiveDwarfFrame = OutStreamer->getNumFrameInfos() &&
+                               !OutStreamer->getDwarfFrameInfos().back().End;
+
     int stackGrowth = -RI->getSlotSize();
 
-    if (NeedsDwarfCFI && !hasFP) {
+    if (HasActiveDwarfFrame && !hasFP) {
       OutStreamer->EmitCFIAdjustCfaOffset(-stackGrowth);
     }
 
@@ -1160,7 +1161,7 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
     EmitAndCountInstruction(MCInstBuilder(X86::POP32r)
                             .addReg(MI->getOperand(0).getReg()));
 
-    if (NeedsDwarfCFI && !hasFP) {
+    if (HasActiveDwarfFrame && !hasFP) {
       OutStreamer->EmitCFIAdjustCfaOffset(stackGrowth);
     }
     return;
diff --git a/llvm/test/CodeGen/X86/pr25828.ll b/llvm/test/CodeGen/X86/pr25828.ll
@@ -0,0 +1,30 @@
+; RUN: llc < %s -mtriple=i686-pc-windows-msvc -relocation-model=pic | FileCheck %s
+; MOVPC32r should not generate CFI under windows
+
+; CHECK-LABEL: _foo:
+; CHECK-NOT: .cfi_adjust_cfa_offset
+define void @foo(i8) {
+entry-block:
+  switch i8 %0, label %bb2 [
+    i8 1, label %bb1
+    i8 2, label %bb2
+    i8 3, label %bb3
+    i8 4, label %bb4
+    i8 5, label %bb5
+  ]
+
+bb1:
+  ret void
+
+bb2:
+  ret void
+
+bb3:
+  ret void
+
+bb4:
+  ret void
+
+bb5:
+  ret void
+}
