[llvm-commits] [llvm] r122248 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp test/Transforms/InstCombine/or.ll

[Benjamin Kramer]

Author: d0k
Date: Mon Dec 20 10:18:51 2010
New Revision: 122248

URL: http://llvm.org/viewvc/llvm-project?rev=122248&view=rev
Log:
Teach InstCombine to merge (icmp ult (X + CA), C1) | (icmp eq X, C2) into (icmp ult (X + CA), C1 + 1) if C2 + CA == C1.

InstCombine creates these so now we compile x == 23 || x == 24 || x == 25 to
  %x.off = add i32 %x, -23
  %1 = icmp ult i32 %x.off, 3
instead of
  %x.off = add i32 %x, -23
  %1 = icmp ult i32 %x.off, 2
  %cmp3 = icmp eq i32 %x, 25
  %ret2 = or i1 %1, %cmp3

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    llvm/trunk/test/Transforms/InstCombine/or.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=122248&r1=122247&r2=122248&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Mon Dec 20 10:18:51 2010
@@ -1450,7 +1450,16 @@
       return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
     }
   }
-  
+
+  // (icmp ult (X + CA), C1) | (icmp eq X, C2) -> (icmp ult (X + CA), C1 + 1)
+  //   iff C2 + CA == C1.
+  if (LHSCC == ICmpInst::ICMP_ULT) {
+    ConstantInt *AddCst;
+    if (match(Val, m_Add(m_Specific(Val2), m_ConstantInt(AddCst))))
+      if (RHSCst->getValue() + AddCst->getValue() == LHSCst->getValue())
+        return Builder->CreateICmp(LHSCC, Val, AddOne(LHSCst));
+  }
+
   // From here on, we only handle:
   //    (icmp1 A, C1) | (icmp2 A, C2) --> something simpler.
   if (Val != Val2) return 0;

Modified: llvm/trunk/test/Transforms/InstCombine/or.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/or.ll?rev=122248&r1=122247&r2=122248&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/or.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/or.ll Mon Dec 20 10:18:51 2010
@@ -376,3 +376,17 @@
   ; CHECK-NEXT: or i32 %a, %b
   ; CHECK-NEXT: or i32 %1, 1135
 }
+
+define i1 @test36(i32 %x) {
+  %cmp1 = icmp eq i32 %x, 23
+  %cmp2 = icmp eq i32 %x, 24
+  %ret1 = or i1 %cmp1, %cmp2
+  %cmp3 = icmp eq i32 %x, 25
+  %ret2 = or i1 %ret1, %cmp3
+  ret i1 %ret2
+; CHECK: @test36
+; CHECK-NEXT: %x.off = add i32 %x, -23
+; CHECK-NEXT: icmp ult i32 %x.off, 3
+; CHECK-NEXT: ret i1
+}
+