[llvm-commits] [llvm] r124567 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/add.ll

[Anders Carlsson]

Author: andersca
Date: Sun Jan 30 16:01:13 2011
New Revision: 124567

URL: http://llvm.org/viewvc/llvm-project?rev=124567&view=rev
Log:
Recognize and simplify

(A+B) == A  ->  B == 0
A == (A+B)  ->  B == 0


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/add.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=124567&r1=124566&r2=124567&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Jan 30 16:01:13 2011
@@ -2341,7 +2341,17 @@
     if (match(Op1, m_Sub(m_Specific(Op0), m_Value(B))))
       return new ICmpInst(I.getPredicate(), B,
                           Constant::getNullValue(B->getType()));
-    
+
+    // (A+B) == A  ->  B == 0
+    if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))))
+      return new ICmpInst(I.getPredicate(), B,
+                          Constant::getNullValue(B->getType()));
+
+    // A == (A+B)  ->  B == 0
+    if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))))
+      return new ICmpInst(I.getPredicate(), B,
+                          Constant::getNullValue(B->getType()));
+
     // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
     if (Op0->hasOneUse() && Op1->hasOneUse() &&
         match(Op0, m_And(m_Value(A), m_Value(B))) && 

Modified: llvm/trunk/test/Transforms/InstCombine/add.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/add.ll?rev=124567&r1=124566&r2=124567&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/add.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/add.ll Sun Jan 30 16:01:13 2011
@@ -275,3 +275,19 @@
 	%q = and i32 %z, 1  ; always zero
 	ret i32 %q
 }
+
+define i32 @test37(i32 %a, i32 %b) nounwind readnone {
+entry:
+  %add = add nsw i32 %a, %b
+  %cmp = icmp eq i32 %add, %a
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+define i32 @test38(i32 %a, i32 %b) nounwind readnone {
+entry:
+  %add = add nsw i32 %a, %b
+  %cmp = icmp eq i32 %add, %a
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}