[MachineOutliner] Test for X86FI->getUsesRedZone() as well as Attribute::NoRedZone

This commit is similar to r329120, but uses the existing getUsesRedZone() function
in X86MachineFunctionInfo. This teaches the outliner to look at whether or not a
function *truly* uses a redzone instead of just the noredzone attribute on a
function.

Thus, after this commit, it's possible to outline from x86 without using
-mno-red-zone and still get outlining results.

This also adds a new test for the new redzone behaviour.

llvm-svn: 329134

2 files changed, 75 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index f5aeb3f10fc..94a0bee7e8e 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -11198,8 +11198,12 @@ bool X86InstrInfo::isFunctionSafeToOutlineFrom(MachineFunction &MF,
 
   // Does the function use a red zone? If it does, then we can't risk messing
   // with the stack.
-  if (!F.hasFnAttribute(Attribute::NoRedZone))
+  if (!F.hasFnAttribute(Attribute::NoRedZone)) {
+    // It could have a red zone. If it does, then we don't want to touch it.
+    const X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
+    if (!X86FI || X86FI->getUsesRedZone())
       return false;
+  }
 
   // If we *don't* want to outline from things that could potentially be deduped
   // then return false.
diff --git a/llvm/test/CodeGen/X86/machine-outliner-noredzone.ll b/llvm/test/CodeGen/X86/machine-outliner-noredzone.ll
new file mode 100644
index 00000000000..94271e30bdf
--- /dev/null
+++ b/llvm/test/CodeGen/X86/machine-outliner-noredzone.ll
@@ -0,0 +1,70 @@
+; RUN: llc -enable-machine-outliner -mtriple=x86_64-apple-darwin < %s | FileCheck %s
+; Ensure that the outliner doesn't outline from any functions that use a redzone.
+
+declare i8* @llvm.stacksave() #1
+declare void @llvm.stackrestore(i8*) #1
+
+; This function has a red zone. We shouldn't outline from it.
+; CHECK-LABEL: doggo
+; CHECK-NOT: OUTLINED
+define void @doggo(i32) #0 {
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = add nsw i32 %3, 1
+  store i32 %4, i32* %2, align 4
+  ret void
+}
+
+; Ditto.
+; CHECK-LABEL: pupper
+; CHECK-NOT: OUTLINED
+define void @pupper(i32) #0 {
+  %2 = alloca i32, align 4
+  store i32 %0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = add nsw i32 %3, 1
+  store i32 %4, i32* %2, align 4
+  ret void
+}
+
+; This doesn't have a redzone. Outlining is okay.
+; CHECK-LABEL: boofer
+; CHECK: OUTLINED
+define void @boofer(i32) #0 {
+  %2 = alloca i32, align 4
+  %3 = alloca i8*, align 8
+  %4 = alloca i64, align 8
+  store i32 %0, i32* %2, align 4
+  %5 = load i32, i32* %2, align 4
+  %6 = zext i32 %5 to i64
+  %7 = call i8* @llvm.stacksave()
+  store i8* %7, i8** %3, align 8
+  %8 = alloca i32, i64 %6, align 16
+  store i64 %6, i64* %4, align 8
+  %9 = load i8*, i8** %3, align 8
+  call void @llvm.stackrestore(i8* %9)
+  ret void
+}
+
+; Ditto.
+; CHECK-LABEL: shibe
+; CHECK: OUTLINED
+define void @shibe(i32) #0 {
+  %2 = alloca i32, align 4
+  %3 = alloca i8*, align 8
+  %4 = alloca i64, align 8
+  store i32 %0, i32* %2, align 4
+  %5 = load i32, i32* %2, align 4
+  %6 = zext i32 %5 to i64
+  %7 = call i8* @llvm.stacksave()
+  store i8* %7, i8** %3, align 8
+  %8 = alloca i32, i64 %6, align 16
+  store i64 %6, i64* %4, align 8
+  %9 = load i8*, i8** %3, align 8
+  call void @llvm.stackrestore(i8* %9)
+  ret void
+}
+
+attributes #0 = { noinline nounwind optnone ssp uwtable "no-frame-pointer-elim"="true" }
+attributes #1 = { nounwind }
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