add support for recursive phi translation and phi

translation of add with immediate.  This allows us
to optimize this function:

void test(int N, double* G) {
  long j;
  G[1] = 1;
    for (j = 1; j < N - 1; j++)
        G[j+1] = G[j] + G[j+1];
}

to only do one load every iteration of the loop.

llvm-svn: 90013

1 files changed, 43 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GVN/pre-load.ll b/llvm/test/Transforms/GVN/pre-load.ll
index 672adaaaeb0..19ea8720d31 100644
--- a/llvm/test/Transforms/GVN/pre-load.ll
+++ b/llvm/test/Transforms/GVN/pre-load.ll
@@ -195,6 +195,49 @@ return:
   ret void
 }
 
+;void test7(int N, double* G) {
+;  long j;
+;  G[1] = 1;
+;  for (j = 1; j < N - 1; j++)
+;      G[j+1] = G[j] + G[j+1];
+;}
+
+; This requires phi translation of the adds.
+define void @test7(i32 %N, double* nocapture %G) nounwind ssp {
+entry:
+  %0 = getelementptr inbounds double* %G, i64 1   
+  store double 1.000000e+00, double* %0, align 8
+  %1 = add i32 %N, -1                             
+  %2 = icmp sgt i32 %1, 1                         
+  br i1 %2, label %bb.nph, label %return
+
+bb.nph:                                           
+  %tmp = sext i32 %1 to i64                       
+  %tmp7 = add i64 %tmp, -1                        
+  br label %bb
+
+bb:                                               
+  %indvar = phi i64 [ 0, %bb.nph ], [ %tmp9, %bb ] 
+  %tmp8 = add i64 %indvar, 2                      
+  %scevgep = getelementptr double* %G, i64 %tmp8  
+  %tmp9 = add i64 %indvar, 1                      
+  %scevgep10 = getelementptr double* %G, i64 %tmp9 
+  %3 = load double* %scevgep10, align 8           
+  %4 = load double* %scevgep, align 8             
+  %5 = fadd double %3, %4                         
+  store double %5, double* %scevgep, align 8
+  %exitcond = icmp eq i64 %tmp9, %tmp7            
+  br i1 %exitcond, label %return, label %bb
+
+; Should only be one load in the loop.
+; CHECK: bb:
+; CHECK: load double*
+; CHECK-NOT: load double*
+; CHECK: br i1 %exitcond
+
+return:                                           
+  ret void
+}
 
 
 ;;; --- todo