[PATCH] D119391: [X86] Only force FP usage in the presence of pushf/popf on Win64

[Reid Kleckner via Phabricator via llvm-commits]

rnk created this revision.
rnk added reviewers: nickdesaulniers, craig.topper.
Herald added subscribers: pengfei, hiraditya.
rnk requested review of this revision.
Herald added a project: LLVM.

This ensures that the Windows unwinder will work at every instruction
boundary, and allows other targets to read and write flags without
setting up a frame pointer.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119391

Files:
  llvm/lib/Target/X86/X86FrameLowering.cpp
  llvm/test/CodeGen/X86/x86-flags-intrinsics.ll


Index: llvm/test/CodeGen/X86/x86-flags-intrinsics.ll
===================================================================
--- llvm/test/CodeGen/X86/x86-flags-intrinsics.ll
+++ llvm/test/CodeGen/X86/x86-flags-intrinsics.ll
@@ -11,11 +11,9 @@
 }
 
 ; CHECK-LABEL: _read_flags:
-; CHECK:      pushl   %ebp
-; CHECK-NEXT: movl    %esp, %ebp
-; CHECK-NEXT: pushfl
+; CHECK:      pushfl
 ; CHECK-NEXT: popl    %eax
-; CHECK-NEXT: popl    %ebp
+; CHECK-NEXT: retl
 
 define x86_fastcallcc void @write_flags(i32 inreg %arg) {
 entry:
@@ -24,8 +22,6 @@
 }
 
 ; CHECK-LABEL: @write_flags at 4:
-; CHECK:      pushl   %ebp
-; CHECK-NEXT: movl    %esp, %ebp
-; CHECK-NEXT: pushl   %ecx
+; CHECK:      pushl   %ecx
 ; CHECK-NEXT: popfl
-; CHECK-NEXT: popl    %ebp
+; CHECK-NEXT: retl
Index: llvm/lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86FrameLowering.cpp
+++ llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -100,7 +100,8 @@
           MF.getInfo<X86MachineFunctionInfo>()->hasPreallocatedCall() ||
           MF.callsUnwindInit() || MF.hasEHFunclets() || MF.callsEHReturn() ||
           MFI.hasStackMap() || MFI.hasPatchPoint() ||
-          MFI.hasCopyImplyingStackAdjustment());
+          (MF.getTarget().getMCAsmInfo()->usesWindowsCFI() &&
+           MFI.hasCopyImplyingStackAdjustment()));
 }
 
 static unsigned getSUBriOpcode(bool IsLP64, int64_t Imm) {


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