InstCombine: Simplify if(x!=0 && x!=-1).

When both constants are positive or both constants are negative,
InstCombine already simplifies comparisons like this, but when
it's exactly zero and -1, the operand sorting ends up reversed
and the pattern fails to match. Handle that special case.

Follow up for rdar://14689217

llvm-svn: 188512

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index b474bd84ca0bcb0c74f471c53ddc9f064d557d6d..bc8506a53843d3797925c4797e83b52cdad7948c 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -849,10 +849,15 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
     case ICmpInst::ICMP_SGT:        // (X != 13 & X s> 15) -> X s> 15
       return RHS;
     case ICmpInst::ICMP_NE:
+      // Special case to get the ordering right when the values wrap around
+      // zero.
+      if (LHSCst->getValue() == 0 && RHSCst->getValue() == -1)
+        std::swap(LHSCst, RHSCst);
       if (LHSCst == SubOne(RHSCst)){// (X != 13 & X != 14) -> X-13 >u 1
         Constant *AddCST = ConstantExpr::getNeg(LHSCst);
         Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
-        return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1));
+        return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1),
+                                      Val->getName()+".cmp");
       }
       break;                        // (X != 13 & X != 15) -> no change
     }

diff --git a/llvm/test/Transforms/InstCombine/and2.ll b/llvm/test/Transforms/InstCombine/and2.ll
index 504391aa48510af55245326620d86be91a5fdc71..e88fd598300335cd4d87c6aae666f57928b7ebb2 100644 (file)
--- a/llvm/test/Transforms/InstCombine/and2.ll
+++ b/llvm/test/Transforms/InstCombine/and2.ll
@@ -42,3 +42,15 @@ define <4 x i32> @test5(<4 x i32> %A) {
   %2 = and <4 x i32> <i32 1, i32 2, i32 3, i32 4>, %1
   ret <4 x i32> %2
 }
+
+; Check that we combine "if x!=0 && x!=-1" into "if x+1u>1"
+define i32 @test6(i64 %x) nounwind {
+; CHECK: @test6
+; CHECK-NEXT: add i64 %x, 1
+; CHECK-NEXT: icmp ugt i64 %x.off, 1
+  %cmp1 = icmp ne i64 %x, -1
+  %not.cmp = icmp ne i64 %x, 0
+  %.cmp1 = and i1 %cmp1, %not.cmp
+  %land.ext = zext i1 %.cmp1 to i32
+  ret i32 %land.ext
+}