[JumpThreading] Restrict PRE across instructions that don't pass control to successors
PRE in JumpThreading should not be able to hoist copy of non-speculable loads across
instructions that don't always transfer execution to their successors, otherwise they may
introduce an unsafe load which otherwise would not be executed.
The same problem for GVN was fixed as rL316975.
Differential Revision: https://reviews.llvm.org/D40347
llvm-svn: 321063
diff --git a/llvm/test/Transforms/JumpThreading/guards.ll b/llvm/test/Transforms/JumpThreading/guards.ll
index 53175a7..c760283 100644
--- a/llvm/test/Transforms/JumpThreading/guards.ll
+++ b/llvm/test/Transforms/JumpThreading/guards.ll
@@ -278,3 +278,106 @@
L3:
ret void
}
+
+; Make sure that we don't PRE a non-speculable load across a guard.
+define void @unsafe_pre_across_guard(i8* %p, i1 %load.is.valid) {
+
+; CHECK-LABEL: @unsafe_pre_across_guard(
+; CHECK-NOT: loaded.pr
+; CHECK: entry:
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %load.is.valid) [ "deopt"() ]
+; CHECK-NEXT: %loaded = load i8, i8* %p
+; CHECK-NEXT: %continue = icmp eq i8 %loaded, 0
+; CHECK-NEXT: br i1 %continue, label %exit, label %loop
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ call void (i1, ...) @llvm.experimental.guard(i1 %load.is.valid) [ "deopt"() ]
+ %loaded = load i8, i8* %p
+ %continue = icmp eq i8 %loaded, 0
+ br i1 %continue, label %exit, label %loop
+
+exit: ; preds = %loop
+ ret void
+}
+
+; Make sure that we can safely PRE a speculable load across a guard.
+define void @safe_pre_across_guard(i8* noalias nocapture readonly dereferenceable(8) %p, i1 %load.is.valid) {
+
+; CHECK-LABEL: @safe_pre_across_guard(
+; CHECK: entry:
+; CHECK-NEXT: %loaded.pr = load i8, i8* %p
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: %loaded = phi i8 [ %loaded, %loop ], [ %loaded.pr, %entry ]
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %load.is.valid) [ "deopt"() ]
+; CHECK-NEXT: %continue = icmp eq i8 %loaded, 0
+; CHECK-NEXT: br i1 %continue, label %exit, label %loop
+
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ call void (i1, ...) @llvm.experimental.guard(i1 %load.is.valid) [ "deopt"() ]
+ %loaded = load i8, i8* %p
+ %continue = icmp eq i8 %loaded, 0
+ br i1 %continue, label %exit, label %loop
+
+exit: ; preds = %loop
+ ret void
+}
+
+; Make sure that we don't PRE a non-speculable load across a call which may
+; alias with the load.
+define void @unsafe_pre_across_call(i8* %p) {
+
+; CHECK-LABEL: @unsafe_pre_across_call(
+; CHECK-NOT: loaded.pr
+; CHECK: entry:
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: call i32 @f1()
+; CHECK-NEXT: %loaded = load i8, i8* %p
+; CHECK-NEXT: %continue = icmp eq i8 %loaded, 0
+; CHECK-NEXT: br i1 %continue, label %exit, label %loop
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ call i32 @f1()
+ %loaded = load i8, i8* %p
+ %continue = icmp eq i8 %loaded, 0
+ br i1 %continue, label %exit, label %loop
+
+exit: ; preds = %loop
+ ret void
+}
+
+; Make sure that we can safely PRE a speculable load across a call.
+define void @safe_pre_across_call(i8* noalias nocapture readonly dereferenceable(8) %p) {
+
+; CHECK-LABEL: @safe_pre_across_call(
+; CHECK: entry:
+; CHECK-NEXT: %loaded.pr = load i8, i8* %p
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: %loaded = phi i8 [ %loaded, %loop ], [ %loaded.pr, %entry ]
+; CHECK-NEXT: call i32 @f1()
+; CHECK-NEXT: %continue = icmp eq i8 %loaded, 0
+; CHECK-NEXT: br i1 %continue, label %exit, label %loop
+
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ call i32 @f1()
+ %loaded = load i8, i8* %p
+ %continue = icmp eq i8 %loaded, 0
+ br i1 %continue, label %exit, label %loop
+
+exit: ; preds = %loop
+ ret void
+}