Fix PR15332 (patch by Florian Zeitz).

There's no need to generate a stack frame for PPC32 SVR4 when there are
no local variables assigned to the stack, i.e., when no red zone is needed.
(PPC64 supports a red zone, but PPC32 does not.)

llvm-svn: 176124

2 files changed, 44 insertions, 4 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
index 6dfb4c8d774..0a396e6693f 100644
--- a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
@@ -207,13 +207,14 @@ void PPCFrameLowering::determineFrameLayout(MachineFunction &MF) const {
   // to adjust the stack pointer (we fit in the Red Zone).  For 64-bit
   // SVR4, we also require a stack frame if we need to spill the CR,
   // since this spill area is addressed relative to the stack pointer.
+  // The 32-bit SVR4 ABI has no Red Zone. However, it can still generate
+  // stackless code if all local vars are reg-allocated.
   bool DisableRedZone = MF.getFunction()->getAttributes().
     hasAttribute(AttributeSet::FunctionIndex, Attribute::NoRedZone);
-  // FIXME SVR4 The 32-bit SVR4 ABI has no red zone.  However, it can
-  // still generate stackless code if all local vars are reg-allocated.
-  // Try: (FrameSize <= 224
-  //       || (FrameSize == 0 && Subtarget.isPPC32 && Subtarget.isSVR4ABI()))
   if (!DisableRedZone &&
+      (Subtarget.isPPC64() ||                      // 32-bit SVR4, no stack-
+       !Subtarget.isSVR4ABI() ||                   //   allocated locals.
+	FrameSize == 0) &&
       FrameSize <= 224 &&                          // Fits in red zone.
       !MFI->hasVarSizedObjects() &&                // No dynamic alloca.
       !MFI->adjustsStack() &&                      // No calls.
diff --git a/llvm/test/CodeGen/PowerPC/svr4-redzone.ll b/llvm/test/CodeGen/PowerPC/svr4-redzone.ll
new file mode 100644
index 00000000000..91ff5797389
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/svr4-redzone.ll
@@ -0,0 +1,39 @@
+; RUN: llc -mtriple="powerpc-unknown-linux-gnu" < %s | FileCheck %s --check-prefix=PPC32
+; RUN: llc -mtriple="powerpc64-unknown-linux-gnu" < %s | FileCheck %s --check-prefix=PPC64
+; PR15332
+
+define void @regalloc() nounwind {
+entry:
+	%0 = add i32 1, 2
+	ret void
+}
+; PPC32: regalloc:
+; PPC32-NOT: stwu 1, -{{[0-9]+}}(1)
+; PPC32: blr
+
+; PPC64: regalloc:
+; PPC64-NOT: stdu 1, -{{[0-9]+}}(1)
+; PPC64: blr
+
+define void @smallstack() nounwind {
+entry:
+	%0 = alloca i8, i32 4
+	ret void
+}
+; PPC32: smallstack:
+; PPC32: stwu 1, -16(1)
+
+; PPC64: smallstack:
+; PPC64-NOT: stdu 1, -{{[0-9]+}}(1)
+; PPC64: blr
+
+define void @bigstack() nounwind {
+entry:
+	%0 = alloca i8, i32 230
+	ret void
+}
+; PPC32: bigstack:
+; PPC32: stwu 1, -240(1)
+
+; PPC64: bigstack:
+; PPC64: stdu 1, -352(1)