[X86] Fix stack probe issue on windows32.

[LuoYuanke]

Summary

On windows if the frame size exceed 4096 bytes, compiler need to generate a call to _alloca_probe. X86CallFrameOptimization pass changes the reserved stack size and cause of stack probe function not be inserted. This patch fix the issue by detecting the call frame size, if the size exceed 4096 bytes, drop X86CallFrameOptimization.

[rnk]

Seems reasonable, but I have some suggestions.

llvm/lib/Target/X86/X86CallFrameOptimization.cpp

247–254

I see this pattern for calculating the stack probe size is already duplicated twice. Please factor it out into a method of X86ISelLowering, perhaps next to getStackProbeSymbolName and update the two callers along with this one.

258–261

I see that TargetInstrInfo uses the phrase "frame size" to refer to the size of the arguments used to pass call arguments, but I think that's easily confused with the size of the current function's stack frame. Maybe this comment would be clearer:

If any call allocates more argument stack memory than the stack probe size, don't do this optimization. Otherwise, this pass would need to synthesize additional stack probe calls to allocate memory for arguments.

263

Please move this check into the isLegal method where other preconditions are checked.

[LuoYuanke]

Update the patch corresponding to Reid's comments.

[rnk]

lgtm, thanks!

llvm/lib/Target/X86/X86CallFrameOptimization.cpp

if (skipFunction(MF.getFunction()) || !isLegal(MF))
     return false;
 
   unsigned FrameSetupOpcode = TII->getCallFrameSetupOpcode();
 
   bool Changed = false;
 
   ContextVector CallSeqVector;
 
+  bool UseStackProbe =
+    !STI->getTargetLowering()->getStackProbeSymbolName(MF).empty();
+  unsigned StackProbeSize = 4096;
+  const Function &Fn = MF.getFunction();
+  if (Fn.hasFnAttribute("stack-probe-size"))
+    Fn.getFnAttribute("stack-probe-size")
+        .getValueAsString()
+        .getAsInteger(0, StackProbeSize);
   for (auto &MBB : MF)
     for (auto &MI : MBB)
       if (MI.getOpcode() == FrameSetupOpcode) {
+        // If the frame size exceed stack probe size, compiler need
+        // to generate a stack probe call . This pass changes the
+        // reserved stack size and cause of stack probe function not
+        // be inserted, so bypass the pass on this scenario.
+        if (TII->getFrameSize(MI) >= StackProbeSize && UseStackProbe)
+          return false;
         CallContext Context;
         collectCallInfo(MF, MBB, MI, Context);
         CallSeqVector.push_back(Context);
       }
 
   if (!isProfitable(MF, CallSeqVector))
     return false;
 

llvm/test/CodeGen/X86/nomovtopush.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=i386-pc-windows-msvc | FileCheck %s
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc"
+
+%struct._param_str = type { i32, i32, [4096 x i32], i32 }
+
+@g_d = common dso_local local_unnamed_addr global i32 0, align 4
+@g_c = common dso_local local_unnamed_addr global i32 0, align 4
+@g_b = common dso_local local_unnamed_addr global i32 0, align 4
+@g_a = common dso_local local_unnamed_addr global i32 0, align 4
+@g_param = common dso_local global %struct._param_str zeroinitializer, align 4
+
+; Function Attrs: nounwind
+define dso_local i32 @test() local_unnamed_addr {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushl %edi
+; CHECK-NEXT:    pushl %esi
+; CHECK-NEXT:    movl $16396, %eax # imm = 0x400C
+; CHECK-NEXT:    calll __chkstk
+; CHECK-NEXT:    movl _g_d, %eax
+; CHECK-NEXT:    movl _g_c, %ecx
+; CHECK-NEXT:    movl _g_b, %edx
+; CHECK-NEXT:    movl _g_a, %esi
+; CHECK-NEXT:    movl %eax, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl %ecx, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl %edx, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl %esi, (%esp)
+; CHECK-NEXT:    calll _bar
+; CHECK-NEXT:    movl $4099, %ecx # imm = 0x1003
+; CHECK-NEXT:    movl %esp, %edi
+; CHECK-NEXT:    movl $_g_param, %esi
+; CHECK-NEXT:    rep;movsl (%esi), %es:(%edi)
+; CHECK-NEXT:    calll _foo
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    addl $16396, %esp # imm = 0x400C
+; CHECK-NEXT:    popl %esi
+; CHECK-NEXT:    popl %edi
+; CHECK-NEXT:    retl
+entry:
+  %0 = load i32, i32* @g_d, align 4, !tbaa !3
+  %1 = load i32, i32* @g_c, align 4, !tbaa !3
+  %2 = load i32, i32* @g_b, align 4, !tbaa !3
+  %3 = load i32, i32* @g_a, align 4, !tbaa !3
+  %call = tail call i32 @bar(i32 %3, i32 %2, i32 %1, i32 %0) #2
+  tail call void @foo(%struct._param_str* byval nonnull align 4 @g_param) #2
+  ret i32 0
+}
+
+declare dso_local i32 @bar(i32, i32, i32, i32) local_unnamed_addr
+
+declare dso_local void @foo(%struct._param_str* byval align 4) local_unnamed_addr
+
+!3 = !{!4, !4, i64 0}
+!4 = !{!"int", !5, i64 0}
+!5 = !{!"omnipotent char", !6, i64 0}
+!6 = !{!"Simple C/C++ TBAA"}