Dereferenceable, dereferenceable_or_null metadata for loads

Summary:
Introduce dereferenceable, dereferenceable_or_null metadata for loads
with the same semantic as corresponding attributes.

This patch depends on http://reviews.llvm.org/D9253

Patch by Artur Pilipenko!

Reviewers: hfinkel, sanjoy, reames

Reviewed By: sanjoy, reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9365

llvm-svn: 237720

2 files changed, 167 insertions, 2 deletions

diff --git a/llvm/test/Analysis/ValueTracking/memory-dereferenceable.ll b/llvm/test/Analysis/ValueTracking/memory-dereferenceable.ll
index 7f178756a8b..c3aba3a7dc0 100644
--- a/llvm/test/Analysis/ValueTracking/memory-dereferenceable.ll
+++ b/llvm/test/Analysis/ValueTracking/memory-dereferenceable.ll
@@ -8,6 +8,7 @@ target datalayout = "e"
 declare zeroext i1 @return_i1()
 
 @globalstr = global [6 x i8] c"hello\00"
+@globali32ptr = external global i32*
 
 define void @test(i32 addrspace(1)* dereferenceable(8) %dparam) gc "statepoint-example" {
 ; CHECK: The following are dereferenceable:
@@ -15,7 +16,12 @@ define void @test(i32 addrspace(1)* dereferenceable(8) %dparam) gc "statepoint-e
 ; CHECK: %alloca
 ; CHECK: %dparam
 ; CHECK: %relocate
+; CHECK: %d4_load
+; CHECK: %d_or_null_non_null_load
 ; CHECK-NOT: %nparam
+; CHECK-NOT: %nd_load
+; CHECK-NOT: %d2_load
+; CHECK-NOT: %d_or_null_load
 entry:
     %globalptr = getelementptr inbounds [6 x i8], [6 x i8]* @globalstr, i32 0, i32 0
     %load1 = load i8, i8* %globalptr
@@ -27,8 +33,33 @@ entry:
     %load4 = load i32, i32 addrspace(1)* %relocate
     %nparam = getelementptr i32, i32 addrspace(1)* %dparam, i32 5
     %load5 = load i32, i32 addrspace(1)* %nparam
+
+    ; Load from a non-dereferenceable load
+    %nd_load = load i32*, i32** @globali32ptr, !dereferenceable !0
+    %load6 = load i32, i32* %nd_load
+
+    ; Load from a dereferenceable load
+    %d4_load = load i32*, i32** @globali32ptr, !dereferenceable !0
+    %load7 = load i32, i32* %d4_load
+
+    ; Load from an offset not covered by the dereferenceable portion
+    %d2_load = load i32*, i32** @globali32ptr, !dereferenceable !1
+    %load8 = load i32, i32* %d2_load
+
+    ; Load from a potentially null pointer with dereferenceable_or_null
+    %d_or_null_load = load i32*, i32** @globali32ptr, !dereferenceable_or_null !0
+    %load9 = load i32, i32* %d_or_null_load
+
+    ; Load from a non-null pointer with dereferenceable_or_null
+    %d_or_null_non_null_load = load i32*, i32** @globali32ptr, !nonnull !2, !dereferenceable_or_null !0
+    %load10 = load i32, i32* %d_or_null_non_null_load
+
     ret void
 }
 
 declare i32 @llvm.experimental.gc.statepoint.p0f_i1f(i64, i32, i1 ()*, i32, i32, ...)
-declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32)
\ No newline at end of file
+declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32)
+
+!0 = !{i64 4}
+!1 = !{i64 2}
+!2 = !{}
diff --git a/llvm/test/Transforms/LICM/hoist-deref-load.ll b/llvm/test/Transforms/LICM/hoist-deref-load.ll
index 9cc03de1fb0..c384a858d1e 100644
--- a/llvm/test/Transforms/LICM/hoist-deref-load.ll
+++ b/llvm/test/Transforms/LICM/hoist-deref-load.ll
@@ -254,5 +254,139 @@ for.end:                                          ; preds = %for.inc, %entry
   ret i1 %not_null
 }
 
-attributes #0 = { nounwind uwtable }
+; This test represents the following function:
+; void test1(int * __restrict__ a, int *b, int **cptr, int n) {
+;   c = *cptr;
+;   for (int i = 0; i < n; ++i)
+;     if (a[i] > 0)
+;       a[i] = (*c)*b[i];
+; }
+; and we want to hoist the load of %c out of the loop. This can be done only
+; because the dereferenceable meatdata on the c = *cptr load.
+
+; CHECK-LABEL: @test7
+; CHECK: load i32, i32* %c, align 4
+; CHECK: for.body:
+
+define void @test7(i32* noalias %a, i32* %b, i32** %cptr, i32 %n) #0 {
+entry:
+  %c = load i32*, i32** %cptr, !dereferenceable !0
+  %cmp11 = icmp sgt i32 %n, 0
+  br i1 %cmp11, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32, i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  %2 = load i32, i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; This test represents the following function:
+; void test1(int * __restrict__ a, int *b, int **cptr, int n) {
+;   c = *cptr;
+;   if (c != null)
+;     for (int i = 0; i < n; ++i)
+;       if (a[i] > 0)
+;         a[i] = (*c)*b[i];
+; }
+; and we want to hoist the load of %c out of the loop. This can be done only
+; because the dereferenceable_or_null meatdata on the c = *cptr load and there 
+; is a null check on %c.
+
+; CHECK-LABEL: @test8
+; CHECK: load i32, i32* %c, align 4
+; CHECK: for.body:
+
+define void @test8(i32* noalias %a, i32* %b, i32** %cptr, i32 %n) #0 {
+entry:
+  %c = load i32*, i32** %cptr, !dereferenceable_or_null !0
+  %not_null = icmp ne i32* %c, null
+  br i1 %not_null, label %not.null, label %for.end
+
+not.null:
+  %cmp11 = icmp sgt i32 %n, 0
+  br i1 %cmp11, label %for.body, label %for.end
+
+for.body:                                         ; preds = %not.null, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %not.null ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32, i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  %2 = load i32, i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry, %not.null
+  ret void
+}
+
+; This is the same as @test8, but without the null check on %c.
+; Without this check, we should not hoist the load of %c.
+
+; CHECK-LABEL: @test9
+; CHECK: if.then:
+; CHECK: load i32, i32* %c, align 4
+
+define void @test9(i32* noalias %a, i32* %b, i32** %cptr, i32 %n) #0 {
+entry:
+  %c = load i32*, i32** %cptr, !dereferenceable_or_null !0
+  %cmp11 = icmp sgt i32 %n, 0
+  br i1 %cmp11, label %for.body, label %for.end
 
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32, i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  %2 = load i32, i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+attributes #0 = { nounwind uwtable }
+!0 = !{i64 4}