[safestack] Sink unsafe address computation to each use.

This is a fix for PR27844.
When replacing uses of unsafe allocas, emit the new location
immediately after each use. Without this, the pointer stays live from
the function entry to the last use, while it's usually cheaper to
recalculate.

llvm-svn: 272969

5 files changed, 66 insertions, 12 deletions

diff --git a/llvm/test/Transforms/SafeStack/array-aligned.ll b/llvm/test/Transforms/SafeStack/array-aligned.ll
index 4676903ec77..26558e4fa81 100644
--- a/llvm/test/Transforms/SafeStack/array-aligned.ll
+++ b/llvm/test/Transforms/SafeStack/array-aligned.ll
@@ -13,16 +13,15 @@ entry:
 
   ; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
 
-  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   %a.addr = alloca i8*, align 8
-
-  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
-  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [16 x i8]*
   %buf = alloca [16 x i8], align 16
 
+  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   ; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
   store i8* %a, i8** %a.addr, align 8
 
+  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
+  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [16 x i8]*
   ; CHECK: %[[GEP:.*]] = getelementptr inbounds [16 x i8], [16 x i8]* %[[BUFPTR2]], i32 0, i32 0
   %gep = getelementptr inbounds [16 x i8], [16 x i8]* %buf, i32 0, i32 0
 
diff --git a/llvm/test/Transforms/SafeStack/array.ll b/llvm/test/Transforms/SafeStack/array.ll
index 564213e6d58..7dcf7fa50d9 100644
--- a/llvm/test/Transforms/SafeStack/array.ll
+++ b/llvm/test/Transforms/SafeStack/array.ll
@@ -17,16 +17,15 @@ entry:
 
   ; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
 
-  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   %a.addr = alloca i8*, align 8
-
-  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -4
-  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [4 x i8]*
   %buf = alloca [4 x i8], align 1
 
+  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   ; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
   store i8* %a, i8** %a.addr, align 8
 
+  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -4
+  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to [4 x i8]*
   ; CHECK: %[[GEP:.*]] = getelementptr inbounds [4 x i8], [4 x i8]* %[[BUFPTR2]], i32 0, i32 0
   %gep = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i32 0, i32 0
 
diff --git a/llvm/test/Transforms/SafeStack/phi.ll b/llvm/test/Transforms/SafeStack/phi.ll
new file mode 100644
index 00000000000..3ee56aa0f56
--- /dev/null
+++ b/llvm/test/Transforms/SafeStack/phi.ll
@@ -0,0 +1,35 @@
+; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
+
+define void @f(i1 %d1, i1 %d2) safestack {
+entry:
+; CHECK-LABEL: define void @f(
+; CHECK:         %[[USP:.*]] = load i8*, i8** @__safestack_unsafe_stack_ptr
+; CHECK-NEXT:    getelementptr i8, i8* %[[USP]], i32 -16
+; CHECK:         br i1 %d1, label %[[BB0:.*]], label %[[BB1:.*]]
+  %a = alloca i32, align 8
+  %b = alloca i32, align 8
+  br i1 %d1, label %bb0, label %bb1
+
+bb0:
+; CHECK: [[BB0]]:
+; CHECK: %[[Ai8:.*]] = getelementptr i8, i8* %unsafe_stack_ptr, i32
+; CHECK: %[[AUNSAFE:.*]] = bitcast i8* %[[Ai8]] to i32*
+; CHECK: br i1
+  br i1 %d2, label %bb2, label %bb2
+
+bb1:
+; CHECK: [[BB1]]:
+; CHECK: %[[Bi8:.*]] = getelementptr i8, i8* %unsafe_stack_ptr, i32
+; CHECK: %[[BUNSAFE:.*]] = bitcast i8* %[[Bi8]] to i32*
+; CHECK: br label
+  br label %bb2
+
+bb2:
+; CHECK: phi i32* [ %[[AUNSAFE]], %[[BB0]] ], [ %[[AUNSAFE]], %[[BB0]] ], [ %[[BUNSAFE]], %[[BB1]] ]
+  %c = phi i32* [ %a, %bb0 ], [ %a, %bb0 ], [ %b, %bb1 ]
+  call void @capture(i32* %c)
+  ret void
+}
+
+declare void @capture(i32*)
diff --git a/llvm/test/Transforms/SafeStack/sink-to-use.ll b/llvm/test/Transforms/SafeStack/sink-to-use.ll
new file mode 100644
index 00000000000..e208ce1da9d
--- /dev/null
+++ b/llvm/test/Transforms/SafeStack/sink-to-use.ll
@@ -0,0 +1,22 @@
+; Test that unsafe alloca address calculation is done immediately before each use.
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
+; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
+
+define void @f() safestack {
+entry:
+  %x0 = alloca i32, align 4
+  %x1 = alloca i32, align 4
+
+; CHECK: %[[A:.*]] = getelementptr i8, i8* %{{.*}}, i32 -4
+; CHECK: %[[X0:.*]] = bitcast i8* %[[A]] to i32*
+; CHECK: call void @use(i32* %[[X0]])
+  call void @use(i32* %x0)
+
+; CHECK: %[[B:.*]] = getelementptr i8, i8* %{{.*}}, i32 -8
+; CHECK: %[[X1:.*]] = bitcast i8* %[[B]] to i32*
+; CHECK: call void @use(i32* %[[X1]])
+  call void @use(i32* %x1)
+  ret void
+}
+
+declare void @use(i32*)
diff --git a/llvm/test/Transforms/SafeStack/struct.ll b/llvm/test/Transforms/SafeStack/struct.ll
index 12a0085a2cc..b64803d160c 100644
--- a/llvm/test/Transforms/SafeStack/struct.ll
+++ b/llvm/test/Transforms/SafeStack/struct.ll
@@ -15,16 +15,15 @@ entry:
 
   ; CHECK: store i8* %[[USST]], i8** @__safestack_unsafe_stack_ptr
 
-  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   %a.addr = alloca i8*, align 8
-
-  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
-  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to %struct.foo*
   %buf = alloca %struct.foo, align 1
 
+  ; CHECK: %[[AADDR:.*]] = alloca i8*, align 8
   ; CHECK: store i8* {{.*}}, i8** %[[AADDR]], align 8
   store i8* %a, i8** %a.addr, align 8
 
+  ; CHECK: %[[BUFPTR:.*]] = getelementptr i8, i8* %[[USP]], i32 -16
+  ; CHECK: %[[BUFPTR2:.*]] = bitcast i8* %[[BUFPTR]] to %struct.foo*
   ; CHECK: %[[GEP:.*]] = getelementptr inbounds %struct.foo, %struct.foo* %[[BUFPTR2]], i32 0, i32 0, i32 0
   %gep = getelementptr inbounds %struct.foo, %struct.foo* %buf, i32 0, i32 0, i32 0