[llvm] 2f7fbf8 - [AArch64] Add missing SEH_Nop when aligning the stack

[Martin Storsjö via llvm-commits]

Author: Martin Storsjö
Date: 2022-10-05T11:00:36+03:00
New Revision: 2f7fbf837625267193351cc334e506a3a9161958

URL: https://github.com/llvm/llvm-project/commit/2f7fbf837625267193351cc334e506a3a9161958
DIFF: https://github.com/llvm/llvm-project/commit/2f7fbf837625267193351cc334e506a3a9161958.diff

LOG: [AArch64] Add missing SEH_Nop when aligning the stack

This makes sure that the instructions of the prologue matches the
SEH opcodes.

Also remove a couple redundant cases of setting HasWinCFI; it was
already set unconditionally after the conditional cases.

Differential Revision: https://reviews.llvm.org/D135101

Added: 
    llvm/test/CodeGen/AArch64/wineh-align-stack.ll

Modified: 
    llvm/lib/Target/AArch64/AArch64InstrInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index 4607a5b2867e2..4167875dbeebb 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -4334,8 +4334,6 @@ static void emitFrameOffsetAdj(MachineBasicBlock &MBB,
       int Imm = (int)(ThisVal << LocalShiftSize);
       if ((DestReg == AArch64::FP && SrcReg == AArch64::SP) ||
           (SrcReg == AArch64::FP && DestReg == AArch64::SP)) {
-        if (HasWinCFI)
-          *HasWinCFI = true;
         if (Imm == 0)
           BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_SetFP)).setMIFlag(Flag);
         else
@@ -4345,12 +4343,13 @@ static void emitFrameOffsetAdj(MachineBasicBlock &MBB,
         assert(Offset == 0 && "Expected remaining offset to be zero to "
                               "emit a single SEH directive");
       } else if (DestReg == AArch64::SP) {
-        if (HasWinCFI)
-          *HasWinCFI = true;
         assert(SrcReg == AArch64::SP && "Unexpected SrcReg for SEH_StackAlloc");
         BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_StackAlloc))
             .addImm(Imm)
             .setMIFlag(Flag);
+      } else {
+        BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
+            .setMIFlag(Flag);
       }
       if (HasWinCFI)
         *HasWinCFI = true;

diff  --git a/llvm/test/CodeGen/AArch64/wineh-align-stack.ll b/llvm/test/CodeGen/AArch64/wineh-align-stack.ll
new file mode 100644
index 0000000000000..0b174a08231c7
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/wineh-align-stack.ll
@@ -0,0 +1,27 @@
+; RUN: llc < %s -mtriple=aarch64-windows | FileCheck %s
+
+define dso_local void @func() {
+entry:
+  %buf = alloca [64 x i8], align 32
+  %arraydecay = getelementptr inbounds [64 x i8], ptr %buf, i64 0, i64 0
+  call void @other(ptr noundef %arraydecay)
+  ret void
+}
+
+declare dso_local void @other(ptr noundef)
+
+; CHECK-LABEL: func:
+; CHECK-NEXT: .seh_proc func
+; CHECK-NEXT: // %bb.0:
+; CHECK-NEXT: stp x29, x30, [sp, #-16]!
+; CHECK-NEXT: .seh_save_fplr_x 16
+; CHECK-NEXT: mov x29, sp
+; CHECK-NEXT: .seh_set_fp
+; CHECK-NEXT: sub x9, sp, #80
+; CHECK-NEXT: .seh_nop
+; CHECK-NEXT: and sp, x9, #0xffffffffffffffe0
+; CHECK-NEXT: .seh_stackalloc 80
+; CHECK-NEXT: .seh_endprologue
+
+; FIXME: Ideally, the SEH prologue wouldn't include the stack realigning
+; instructions at all, but it's enough to end the prologue after .seh_set_fp.