[safestack] Fix compiler crash in the presence of stack restores.

A use can be emitted before def in a function with stack restore
points but no static allocas.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248455 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SafeStack/ARM/setjmp.ll

@@ -0,0 +1,34 @@
+; Test stack pointer restore after setjmp() with the function-call safestack ABI.
+; RUN: opt -safe-stack -S -mtriple=arm-linux-androideabi < %s -o - | FileCheck %s
+
+@env = global [64 x i32] zeroinitializer, align 4
+
+define void @f(i32 %b) safestack {
+entry:
+; CHECK: %[[SPA:.*]] = call i8** @__safestack_pointer_address()
+; CHECK: %[[USDP:.*]] = alloca i8*
+; CHECK: %[[USP:.*]] = load i8*, i8** %[[SPA]]
+; CHECK: store i8* %[[USP]], i8** %[[USDP]]
+; CHECK: call i32 @setjmp
+
+  %call = call i32 @setjmp(i32* getelementptr inbounds ([64 x i32], [64 x i32]* @env, i32 0, i32 0)) returns_twice
+
+; CHECK: %[[USP2:.*]] = load i8*, i8** %[[USDP]]
+; CHECK: store i8* %[[USP2]], i8** %[[SPA]]
+
+  %tobool = icmp eq i32 %b, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  %0 = alloca [42 x i8], align 1
+  %.sub = getelementptr inbounds [42 x i8], [42 x i8]* %0, i32 0, i32 0
+  call void @_Z7CapturePv(i8* %.sub)
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+declare i32 @setjmp(i32*) returns_twice
+
+declare void @_Z7CapturePv(i8*)