[TRE] Improve code motion in TRE, use AA to tell whether a load can be moved before a call that writes to memory.

Summary: use AA to tell whether a load can be moved before a call that writes to memory.

Reviewers: dberlin, davide, sanjoy, hfinkel

Reviewed By: hfinkel

Subscribers: hfinkel, llvm-commits

Differential Revision: https://reviews.llvm.org/D34115

llvm-svn: 305698

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/test/Transforms/TailCallElim/reorder_load.ll b/llvm/test/Transforms/TailCallElim/reorder_load.ll
index 2f9b692d099..78621b105f5 100644
--- a/llvm/test/Transforms/TailCallElim/reorder_load.ll
+++ b/llvm/test/Transforms/TailCallElim/reorder_load.ll
@@ -7,6 +7,7 @@ target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 ; then eliminate the tail recursion.
 
 
+
 @global = external global i32		; <i32*> [#uses=1]
 @extern_weak_global = extern_weak global i32		; <i32*> [#uses=1]
 
@@ -145,3 +146,29 @@ else:		; preds = %entry
 	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=1]
 	ret i32 %tmp10
 }
+
+; This load can be moved above the call because the function call does not write to the memory the load
+; is accessing and the load is safe to speculate.
+define fastcc i32 @raise_load_6(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) nounwind  {
+; CHECK-LABEL: @raise_load_6(
+; CHECK-NOT: call
+; CHECK: load i32, i32*
+; CHECK-NOT: call
+; CHECK: }
+entry:
+  %s = alloca i32
+  store i32 4, i32* %s
+	%tmp2 = icmp sge i32 %start_arg, %a_len_arg		; <i1> [#uses=1]
+	br i1 %tmp2, label %if, label %else
+
+if:		; preds = %entry
+  store i32 1, i32* %a_arg
+	ret i32 0
+
+else:		; preds = %entry
+	%tmp7 = add i32 %start_arg, 1		; <i32> [#uses=1]
+	%tmp8 = call fastcc i32 @raise_load_6(i32* %a_arg, i32 %a_len_arg, i32 %tmp7)		; <i32> [#uses=1]
+	%tmp9 = load i32, i32* %s		; <i32> [#uses=1]
+	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=1]
+	ret i32 %tmp10
+}