[llvm-commits] [llvm] r158237 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAddSub.cpp test/Transforms/InstCombine/pr12338.ll

[Nuno Lopes]

Author: nlopes
Date: Fri Jun  8 17:30:05 2012
New Revision: 158237

URL: http://llvm.org/viewvc/llvm-project?rev=158237&view=rev
Log:
canonicalize:
-%a + 42
into
42 - %a

previously we were emitting:
-(%a + 42)

This fixes the infinite loop in PR12338. The generated code is still not perfect, though.
Will work on that next

Added:
    llvm/trunk/test/Transforms/InstCombine/pr12338.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=158237&r1=158236&r2=158237&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Fri Jun  8 17:30:05 2012
@@ -170,10 +170,11 @@
   // -A + B  -->  B - A
   // -A + -B  -->  -(A + B)
   if (Value *LHSV = dyn_castNegVal(LHS)) {
-    if (Value *RHSV = dyn_castNegVal(RHS)) {
-      Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
-      return BinaryOperator::CreateNeg(NewAdd);
-    }
+    if (!isa<Constant>(RHS))
+      if (Value *RHSV = dyn_castNegVal(RHS)) {
+        Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
+        return BinaryOperator::CreateNeg(NewAdd);
+      }
     
     return BinaryOperator::CreateSub(RHS, LHSV);
   }

Added: llvm/trunk/test/Transforms/InstCombine/pr12338.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/pr12338.ll?rev=158237&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/pr12338.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/pr12338.ll Fri Jun  8 17:30:05 2012
@@ -0,0 +1,24 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define void @entry() nounwind {
+entry:
+  br label %for.cond
+
+for.cond:
+  %local = phi <1 x i32> [ <i32 0>, %entry ], [ %phi2, %cond.end47 ]
+; CHECK: sub <1 x i32> <i32 92>, %local
+  %phi3 = sub <1 x i32> zeroinitializer, %local
+  br label %cond.end
+
+cond.false:
+  br label %cond.end
+
+cond.end:
+  %cond = phi <1 x i32> [ %phi3, %for.cond ], [ undef, %cond.false ]
+  br label %cond.end47
+
+cond.end47:
+  %sum = add <1 x i32> %cond, <i32 92>
+  %phi2 = sub <1 x i32> zeroinitializer, %sum
+  br label %for.cond
+}