From: Eli Friedman <efriedma@quicinc.com>
Date: Thu, 28 Feb 2019 20:38:45 +0000 (+0000)
Subject: [AArch64] [Windows] Don't skip constructing UnwindHelp.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=66161202dd3a5e2732125b0d84b8586f413f0ed8;p=llvm

[AArch64] [Windows] Don't skip constructing UnwindHelp.

In certain cases, the first non-frame-setup instruction in a function is
a branch.  For example, it could be a cbz on an argument.  Make sure we
correctly allocate the UnwindHelp, and find an appropriate register to
use to initialize it.

Fixes https://bugs.llvm.org/show_bug.cgi?id=40184

Differential Revision: https://reviews.llvm.org/D58752



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355136 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/AArch64/AArch64FrameLowering.cpp b/lib/Target/AArch64/AArch64FrameLowering.cpp
index 446e1928d26..597b25cba1c 100644
--- a/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -2142,9 +2142,6 @@ void AArch64FrameLowering::processFunctionBeforeFrameFinalized(
   while (MBBI != MBB.end() && MBBI->getFlag(MachineInstr::FrameSetup))
     ++MBBI;
 
-  if (MBBI->isTerminator())
-    return;
-
   // Create an UnwindHelp object.
   int UnwindHelpFI =
       MFI.CreateStackObject(/*size*/8, /*alignment*/16, false);
@@ -2152,8 +2149,10 @@ void AArch64FrameLowering::processFunctionBeforeFrameFinalized(
   // We need to store -2 into the UnwindHelp object at the start of the
   // function.
   DebugLoc DL;
-  RS->enterBasicBlock(MBB);
-  unsigned DstReg = RS->scavengeRegister(&AArch64::GPR64RegClass, MBBI, 0);
+  RS->enterBasicBlockEnd(MBB);
+  RS->backward(std::prev(MBBI));
+  unsigned DstReg = RS->FindUnusedReg(&AArch64::GPR64commonRegClass);
+  assert(DstReg && "There must be a free register after frame setup");
   BuildMI(MBB, MBBI, DL, TII.get(AArch64::MOVi64imm), DstReg).addImm(-2);
   BuildMI(MBB, MBBI, DL, TII.get(AArch64::STURXi))
       .addReg(DstReg, getKillRegState(true))
diff --git a/test/CodeGen/AArch64/seh-finally.ll b/test/CodeGen/AArch64/seh-finally.ll
index 2a7b2a925f3..b6dfc6e8567 100644
--- a/test/CodeGen/AArch64/seh-finally.ll
+++ b/test/CodeGen/AArch64/seh-finally.ll
@@ -36,8 +36,8 @@ define void @simple_seh() #0 personality i8* bitcast (i32 (...)* @__C_specific_h
 entry:
 ; CHECK-LABEL: simple_seh
 ; CHECK: add     x29, sp, #16
-; CHECK: orr     x1, xzr, #0xfffffffffffffffe
-; CHECK: stur    x1, [x29, #-16]
+; CHECK: orr     x0, xzr, #0xfffffffffffffffe
+; CHECK: stur    x0, [x29, #-16]
 ; CHECK: .set .Lsimple_seh$frame_escape_0, -8
 ; CHECK: ldur    w0, [x29, #-8]
 ; CHECK: bl      foo
@@ -90,8 +90,8 @@ entry:
 ; CHECK: sub     x9, sp, #64
 ; CHECK: and     sp, x9, #0xffffffffffffffe0
 ; CHECK: mov     x19, sp
-; CHECK: orr     x1, xzr, #0xfffffffffffffffe
-; CHECK: stur    x1, [x19, #16]
+; CHECK: orr     x0, xzr, #0xfffffffffffffffe
+; CHECK: stur    x0, [x19, #16]
 ; CHECK: .set .Lstack_realign$frame_escape_0, 32
 ; CHECK: ldr     w0, [x19, #32]
 ; CHECK: bl      foo
diff --git a/test/CodeGen/AArch64/wineh-try-catch-cbz.ll b/test/CodeGen/AArch64/wineh-try-catch-cbz.ll
new file mode 100644
index 00000000000..7c64328f0a7
--- /dev/null
+++ b/test/CodeGen/AArch64/wineh-try-catch-cbz.ll
@@ -0,0 +1,40 @@
+; RUN: llc < %s | FileCheck %s
+
+; Make sure the prologue is sane.  (Doesn't need to exactly match this,
+; but the original issue only reproduced if the cbz was immediately
+; after the frame setup.)
+
+; CHECK:      sub     sp, sp, #32
+; CHECK-NEXT: stp     x29, x30, [sp, #16]
+; CHECK-NEXT: add     x29, sp, #16
+; CHECK-NEXT: orr     x1, xzr, #0xfffffffffffffffe
+; CHECK-NEXT: stur    x1, [x29, #-16]
+; CHECK-NEXT: cbz     w0, .LBB0_2
+
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-windows-msvc19.11.0"
+
+; Function Attrs: uwtable
+define dso_local void @"?f@@YAXH@Z"(i32 %x) local_unnamed_addr #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %cmp = icmp eq i32 %x, 0
+  br i1 %cmp, label %try.cont, label %if.then
+
+if.then:                                          ; preds = %entry
+  invoke void @"?g@@YAXXZ"()
+          to label %try.cont unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %if.then
+  %0 = catchswitch within none [label %catch] unwind to caller
+
+catch:                                            ; preds = %catch.dispatch
+  %1 = catchpad within %0 [i8* null, i32 64, i8* null]
+  catchret from %1 to label %try.cont
+
+try.cont:                                         ; preds = %entry, %if.then, %catch
+  ret void
+}
+
+declare dso_local void @"?g@@YAXXZ"() local_unnamed_addr #1
+
+declare dso_local i32 @__CxxFrameHandler3(...)
diff --git a/test/CodeGen/AArch64/wineh-try-catch.ll b/test/CodeGen/AArch64/wineh-try-catch.ll
index 940a86282d3..f4bb9d50a43 100644
--- a/test/CodeGen/AArch64/wineh-try-catch.ll
+++ b/test/CodeGen/AArch64/wineh-try-catch.ll
@@ -22,8 +22,8 @@
 ; CHECK:       add     x29, sp, #32
 ; CHECK:       sub     sp, sp, #624
 ; CHECK:       mov     x19, sp
-; CHECK:       orr     x1, xzr, #0xfffffffffffffffe
-; CHECK:       stur    x1, [x19]
+; CHECK:       orr     x0, xzr, #0xfffffffffffffffe
+; CHECK:       stur    x0, [x19]
 
 ; Now check that x is stored at fp - 20.  We check that this is the same
 ; location accessed from the funclet to retrieve x.