[PATCH] [AArch64] Fix NZCV reg live-in bug in F128CSEL codegen

[Amara Emerson]

Hi t.p.northover,

When generating the IfTrue basic block during the F128CSEL pseudo-instruction handling, the NZCV live-in for the newly created BB wasn't being added. This caused a fault during MI-sched/live range calculation when the predecessor for the fall-through BB didn't have a live-in for phys-reg as expected.

Review appreciated.

http://llvm-reviews.chandlerc.com/D1949

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  test/CodeGen/AArch64/fp128-livein.ll

Index: lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.cpp
+++ lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -699,6 +699,12 @@
   MBB->addSuccessor(TrueBB);
   MBB->addSuccessor(EndBB);
 
+  if (!NZCVKilled) {
+    // NZCV is live-through TrueBB.
+    TrueBB->addLiveIn(AArch64::NZCV);
+    EndBB->addLiveIn(AArch64::NZCV);
+  }
+
   // IfTrue:
   //     str qIFTRUE, [sp]
   BuildMI(TrueBB, DL, TII->get(AArch64::LSFP128_STR))
@@ -713,8 +719,6 @@
   // Done:
   //     ldr qDEST, [sp]
   //     [... rest of incoming MBB ...]
-  if (!NZCVKilled)
-    EndBB->addLiveIn(AArch64::NZCV);
   MachineInstr *StartOfEnd = EndBB->begin();
   BuildMI(*EndBB, StartOfEnd, DL, TII->get(AArch64::LSFP128_LDR), DestReg)
     .addFrameIndex(ScratchFI)
Index: test/CodeGen/AArch64/fp128-livein.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AArch64/fp128-livein.ll
@@ -0,0 +1,17 @@
+; RUN: llc -mtriple=aarch64-none-linux-gnu -verify-machineinstrs < %s
+
+; Regression test for NZCV reg live-in not being added to fp128csel IfTrue BB,
+; causing a crash during live range calc.
+define void @fp128_livein(i64 %a) {
+  %tobool = icmp ne i64 %a, 0
+  %conv = zext i1 %tobool to i32
+  %conv2 = sitofp i32 %conv to fp128
+  %conv6 = sitofp i32 %conv to double
+  %call3 = tail call i32 @g(fp128 %conv2)
+  %call8 = tail call i32 @h(double %conv6)
+  ret void
+}
+
+declare i32 @f()
+declare i32 @g(fp128)
+declare i32 @h(double)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D1949.1.patch
Type: text/x-patch
Size: 1572 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20131016/d359b66b/attachment.bin>