[SystemZ][z/OS] Save (and restore) R3 to avoid clobbering parameter when call stack...

When the stack frame extension routine is used, the contents of r3 is overwritten.
However, if r3 is live in the prologue (ie. one of the function's parameters
resides in r3), it needs to be saved. We save r3 in r0 if r0 is available
(ie. r0 is not used as temporary storage for r4), and in the corresponding
stack slot for the third parameter otherwise.

Differential Revision: https://reviews.llvm.org/D150332

Reviewed By: uweigand

diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index d7a2a51..11a59df 100644 (file)
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -1315,6 +1315,10 @@ void SystemZXPLINKFrameLowering::inlineStackProbe(
   if (StackAllocMI == nullptr)
     return;
 
+  bool NeedSaveSP = hasFP(MF);
+  bool NeedSaveArg = PrologMBB.isLiveIn(SystemZ::R3D);
+  const int64_t SaveSlotR3 = 2192;
+
   MachineBasicBlock &MBB = PrologMBB;
   const DebugLoc DL = StackAllocMI->getDebugLoc();
 
@@ -1334,7 +1338,25 @@ void SystemZXPLINKFrameLowering::inlineStackProbe(
   // BASR r3,r3
   BuildMI(StackExtMBB, DL, ZII->get(SystemZ::CallBASR_STACKEXT))
       .addReg(SystemZ::R3D);
-
+  if (NeedSaveArg) {
+    if (!NeedSaveSP) {
+      // LGR r0,r3
+      BuildMI(MBB, StackAllocMI, DL, ZII->get(SystemZ::LGR))
+          .addReg(SystemZ::R0D, RegState::Define)
+          .addReg(SystemZ::R3D);
+    } else {
+      // In this case, the incoming value of r4 is saved in r0 so the
+      // latter register is unavailable. Store r3 in its corresponding
+      // slot in the parameter list instead. Do this at the start of
+      // the prolog before r4 is manipulated by anything else.
+      // STG r3, 2192(r4)
+      BuildMI(MBB, MBB.begin(), DL, ZII->get(SystemZ::STG))
+          .addReg(SystemZ::R3D)
+          .addReg(SystemZ::R4D)
+          .addImm(SaveSlotR3)
+          .addReg(0);
+    }
+  }
   // LLGT r3,1208
   BuildMI(MBB, StackAllocMI, DL, ZII->get(SystemZ::LLGT), SystemZ::R3D)
       .addReg(0)
@@ -1355,6 +1377,28 @@ void SystemZXPLINKFrameLowering::inlineStackProbe(
   NextMBB = SystemZ::splitBlockBefore(StackAllocMI, &MBB);
   MBB.addSuccessor(NextMBB);
   MBB.addSuccessor(StackExtMBB);
+  if (NeedSaveArg) {
+    if (!NeedSaveSP) {
+      // LGR r3, r0
+      BuildMI(*NextMBB, StackAllocMI, DL, ZII->get(SystemZ::LGR))
+          .addReg(SystemZ::R3D, RegState::Define)
+          .addReg(SystemZ::R0D, RegState::Kill);
+    } else {
+      // In this case, the incoming value of r4 is saved in r0 so the
+      // latter register is unavailable. We stored r3 in its corresponding
+      // slot in the parameter list instead and we now restore it from there.
+      // LGR r3, r0
+      BuildMI(*NextMBB, StackAllocMI, DL, ZII->get(SystemZ::LGR))
+          .addReg(SystemZ::R3D, RegState::Define)
+          .addReg(SystemZ::R0D);
+      // LG r3, 2192(r3)
+      BuildMI(*NextMBB, StackAllocMI, DL, ZII->get(SystemZ::LG))
+          .addReg(SystemZ::R3D, RegState::Define)
+          .addReg(SystemZ::R3D)
+          .addImm(SaveSlotR3)
+          .addReg(0);
+    }
+  }
 
   // Add jump back from stack extension BB.
   BuildMI(StackExtMBB, DL, ZII->get(SystemZ::J)).addMBB(NextMBB);

diff --git a/llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll b/llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll
index f074a26..13224c0 100644 (file)
--- a/llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll
+++ b/llvm/test/CodeGen/SystemZ/zos-prologue-epilog.ll
@@ -319,12 +319,57 @@ define i64 @func5(i64 %n) {
 ; CHECK64: lg  3, 72(3)
 ; CHECK64: basr  3, 3
 ; CHECK64: stmg  6, 7, 2064(4)
-define void @large_stack() {
+define void @large_stack0() {
   %arr = alloca [131072 x i64], align 8
   call i64 (ptr) @fun1(ptr %arr)
   ret void
 }
 
+; CHECK-LABEL: large_stack1
+; CHECK64: agfi  4, -1048768
+; CHECK64: lgr 0, 3
+; CHECK64: llgt  3, 1208
+; CHECK64: cg  4, 64(3)
+; CHECK64: jhe @BB7_2
+; CHECK64: %bb.1:
+; CHECK64: lg  3, 72(3)
+; CHECK64: basr  3, 3
+; CHECK64: bcr 0, 7
+; CHECK64: @BB7_2:
+; CHECK64: stmg  6, 7, 2064(4)
+; CHECK64: lgr 3, 0
+define void @large_stack1(i64 %n1, i64 %n2, i64 %n3) {
+  %arr = alloca [131072 x i64], align 8
+  call i64 (ptr, i64, i64, i64) @fun3(ptr %arr,
+            i64 %n1, i64 %n2, i64 %n3)
+  ret void
+}
+
+
+; CHECK-LABEL: large_stack2
+; CHECK64: lgr 0, 4
+; CHECK64: stg 3, 2192(4)
+; CHECK64: agfi  4, -1048768
+; CHECK64: llgt  3, 1208
+; CHECK64: cg  4, 64(3)
+; CHECK64: jhe @BB8_2
+; CHECK64: %bb.1:
+; CHECK64: lg  3, 72(3)
+; CHECK64: basr  3, 3
+; CHECK64: bcr 0, 7
+; CHECK64: @BB8_2:
+; CHECK64: lgr 3, 0
+; CHECK64: lg  3, 2192(3)
+; CHECK64: stmg  4, 11, 2048(4)
+; CHECK64: lgr 8, 4
+define void @large_stack2(i64 %n1, i64 %n2, i64 %n3) {
+  %arr0 = alloca [131072 x i64], align 8
+  %arr1 = alloca i64, i64 %n1, align 8
+  call i64 (ptr, ptr, i64, i64, i64) @fun4(ptr %arr0,
+            ptr %arr1, i64 %n1, i64 %n2, i64 %n3)
+  ret void
+}
+
 ; CHECK-LABEL: leaf_func
 ; CHECK-NOT: aghi  4,
 ; CHECK-NOT: stmg
@@ -343,3 +388,5 @@ define i64 @leaf_func0(i64 %a, i64 %b, i64 %c) {
 declare i64 @fun(i64 %arg0)
 declare i64 @fun1(ptr %ptr)
 declare i64 @fun2(i64 %n, ptr %arr0, ptr %arr1)
+declare i64 @fun3(ptr %ptr, i64 %n1, i64 %n2, i64 %n3)
+declare i64 @fun4(ptr %ptr0, ptr %ptr1, i64 %n1, i64 %n2, i64 %n3)