[llvm-commits] [llvm] r130405 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp test/Transforms/InstCombine/merge-icmp.ll

[Benjamin Kramer]

Author: d0k
Date: Thu Apr 28 11:58:40 2011
New Revision: 130405

URL: http://llvm.org/viewvc/llvm-project?rev=130405&view=rev
Log:
InstCombine: Merge "(trunc x) == C1 & (and x, CA) == C2" into a single and+icmp.

This happens when GVN widens loads. Part of PR6627.

Added:
    llvm/trunk/test/Transforms/InstCombine/merge-icmp.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=130405&r1=130404&r2=130405&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Thu Apr 28 11:58:40 2011
@@ -769,6 +769,42 @@
       return Builder->CreateICmp(LHSCC, NewOr, LHSCst);
     }
   }
+
+  // (trunc x) == C1 & (and x, CA) == C2 -> (and CA|CMAX) == C1|C2
+  // where CMAX is the all ones value for the truncated type,
+  // iff the lower bits of CA are zero.
+  if (LHSCC == RHSCC && ICmpInst::isEquality(LHSCC) &&
+      LHS->hasOneUse() && RHS->hasOneUse()) {
+    Value *V;
+    ConstantInt *AndCst, *SmallCst = 0, *BigCst = 0;
+
+    // (trunc x) == C1 & (and x, CA) == C2
+    if (match(Val2, m_Trunc(m_Value(V))) &&
+        match(Val, m_And(m_Specific(V), m_ConstantInt(AndCst)))) {
+      SmallCst = RHSCst;
+      BigCst = LHSCst;
+    }
+    // (and x, CA) == C2 & (trunc x) == C1
+    else if (match(Val, m_Trunc(m_Value(V))) &&
+             match(Val2, m_And(m_Specific(V), m_ConstantInt(AndCst)))) {
+      SmallCst = LHSCst;
+      BigCst = RHSCst;
+    }
+
+    if (SmallCst && BigCst) {
+      unsigned BigBitSize = BigCst->getType()->getBitWidth();
+      unsigned SmallBitSize = SmallCst->getType()->getBitWidth();
+
+      // Check that the low bits are zero.
+      APInt Low = APInt::getLowBitsSet(BigBitSize, SmallBitSize);
+      if ((Low & AndCst->getValue()) == 0) {
+        Value *NewAnd = Builder->CreateAnd(V, Low | AndCst->getValue());
+        APInt N = SmallCst->getValue().zext(BigBitSize) | BigCst->getValue();
+        Value *NewVal = ConstantInt::get(AndCst->getType()->getContext(), N);
+        return Builder->CreateICmp(LHSCC, NewAnd, NewVal);
+      }
+    }
+  }
   
   // From here on, we only handle:
   //    (icmp1 A, C1) & (icmp2 A, C2) --> something simpler.

Added: llvm/trunk/test/Transforms/InstCombine/merge-icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/merge-icmp.ll?rev=130405&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/merge-icmp.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/merge-icmp.ll Thu Apr 28 11:58:40 2011
@@ -0,0 +1,29 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+define i1 @test1(i16* %x) {
+  %load = load i16* %x, align 4
+  %trunc = trunc i16 %load to i8
+  %cmp1 = icmp eq i8 %trunc, 127
+  %and = and i16 %load, -256
+  %cmp2 = icmp eq i16 %and, 17664
+  %or = and i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK: @test1
+; CHECK-NEXT: load i16
+; CHECK-NEXT: icmp eq i16 %load, 17791
+; CHECK-NEXT: ret i1
+}
+
+define i1 @test2(i16* %x) {
+  %load = load i16* %x, align 4
+  %and = and i16 %load, -256
+  %cmp1 = icmp eq i16 %and, 32512
+  %trunc = trunc i16 %load to i8
+  %cmp2 = icmp eq i8 %trunc, 69
+  %or = and i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK: @test2
+; CHECK-NEXT: load i16
+; CHECK-NEXT: icmp eq i16 %load, 32581
+; CHECK-NEXT: ret i1
+}