[MachineSink] Don't break ImplicitNulls

Summary:
This teaches MachineSink to not sink instructions that might break the
implicit null check optimization that runs later.  This should not
affect frontends that do not use implicit null checks.

Reviewers: aadg, reames, hfinkel, atrick

Subscribers: majnemer, llvm-commits

Differential Revision: http://reviews.llvm.org/D14632

llvm-svn: 258254

1 files changed, 49 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/machine-sink-and-implicit-null-checks.ll b/llvm/test/CodeGen/X86/machine-sink-and-implicit-null-checks.ll
new file mode 100644
index 00000000000..0d3bd06d095
--- /dev/null
+++ b/llvm/test/CodeGen/X86/machine-sink-and-implicit-null-checks.ll
@@ -0,0 +1,49 @@
+; RUN: llc -mtriple=x86_64-apple-macosx -O3 -enable-implicit-null-checks -o - < %s 2>&1 | FileCheck %s
+
+declare void @throw0()
+declare void @throw1()
+
+define i1 @f(i8* %p0, i8* %p1) {
+ entry:
+  %c0 = icmp eq i8* %p0, null
+  br i1 %c0, label %throw0, label %continue0, !make.implicit !0
+
+ continue0:
+  %v0 = load i8, i8* %p0
+  %c1 = icmp eq i8* %p1, null
+  br i1 %c1, label %throw1, label %continue1, !make.implicit !0
+
+ continue1:
+  %v1 = load i8, i8* %p1
+  %v = icmp eq i8 %v0, %v1
+  ret i1 %v
+
+ throw0:
+  call void @throw0()
+  unreachable
+
+ throw1:
+  call void @throw1()
+  unreachable
+}
+
+; Check that we have two implicit null checks in @f
+
+; CHECK: __LLVM_FaultMaps:
+; CHECK-NEXT:        .byte   1
+; CHECK-NEXT:        .byte   0
+; CHECK-NEXT:        .short  0
+; CHECK-NEXT:        .long   1
+
+; FunctionInfo[0] =
+
+; FunctionAddress =
+; CHECK-NEXT:        .quad   _f
+
+; NumFaultingPCs =
+; CHECK-NEXT:        .long   2
+
+; Reserved =
+; CHECK-NEXT:        .long   0
+
+!0 = !{}