[llvm-commits] [llvm] r171537 - in /llvm/trunk: lib/Transforms/Vectorize/LoopVectorize.cpp test/Transforms/LoopVectorize/gcc-examples.ll test/Transforms/LoopVectorize/reduction.ll

[Paul Redmond]

Author: predmond
Date: Fri Jan  4 16:10:16 2013
New Revision: 171537

URL: http://llvm.org/viewvc/llvm-project?rev=171537&view=rev
Log:
Do not vectorize loops with subtraction reductions

Since subtraction does not commute the loop vectorizer incorrectly vectorizes
reductions such as x = A[i] - x.

Disabling for now.

Modified:
    llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/trunk/test/Transforms/LoopVectorize/gcc-examples.ll
    llvm/trunk/test/Transforms/LoopVectorize/reduction.ll

Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=171537&r1=171536&r2=171537&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Fri Jan  4 16:10:16 2013
@@ -1986,7 +1986,6 @@
     // possibly.
     return true;
   case Instruction::Add:
-  case Instruction::Sub:
     return Kind == IntegerAdd;
   case Instruction::Mul:
     return Kind == IntegerMult;

Modified: llvm/trunk/test/Transforms/LoopVectorize/gcc-examples.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/gcc-examples.ll?rev=171537&r1=171536&r2=171537&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/gcc-examples.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/gcc-examples.ll Fri Jan  4 16:10:16 2013
@@ -241,7 +241,7 @@
 }
 
 ;CHECK: @example9
-;CHECK: phi <4 x i32>
+;CHECK-NOT: phi <4 x i32>
 ;CHECK: ret i32
 define i32 @example9() nounwind uwtable readonly ssp {
   br label %1

Modified: llvm/trunk/test/Transforms/LoopVectorize/reduction.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/reduction.ll?rev=171537&r1=171536&r2=171537&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/reduction.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/reduction.ll Fri Jan  4 16:10:16 2013
@@ -270,3 +270,53 @@
   %result.0.lcssa = phi i32 [ 0, %entry ], [ %xor, %for.body ]
   ret i32 %result.0.lcssa
 }
+
+;CHECK: @reduction_sub_rhs
+;CHECK-NOT: phi <4 x i32>
+;CHECK-NOT: sub nsw <4 x i32>
+;CHECK: ret i32
+define i32 @reduction_sub_rhs(i32 %n, i32* noalias nocapture %A) nounwind uwtable readonly {
+entry:
+  %cmp3 = icmp sgt i32 %n, 0
+  br i1 %cmp3, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %x.04 = phi i32 [ %sub, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %A, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %sub = sub nsw i32 %x.04, %0
+  %indvars.iv.next = add 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.body, %entry
+  %x.0.lcssa = phi i32 [ 0, %entry ], [ %sub, %for.body ]
+  ret i32 %x.0.lcssa
+}
+
+;CHECK: @reduction_sub_lhs
+;CHECK-NOT: phi <4 x i32>
+;CHECK-NOT: sub nsw <4 x i32>
+;CHECK: ret i32
+define i32 @reduction_sub_lhs(i32 %n, i32* noalias nocapture %A) nounwind uwtable readonly {
+entry:
+  %cmp4 = icmp sgt i32 %n, 0
+  br i1 %cmp4, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %x.05 = phi i32 [ %sub, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %A, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %sub = sub nsw i32 %0, %x.05
+  %indvars.iv.next = add 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.body, %entry
+  %x.0.lcssa = phi i32 [ 0, %entry ], [ %sub, %for.body ]
+  ret i32 %x.0.lcssa
+}