From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 9 Jul 2013 07:50:59 +0000 (+0000)
Subject: InstCombine: add more transforms
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=377a5c1a87b879b7a05a635ed7bbf125b0b61e28;p=oota-llvm.git

InstCombine: add more transforms

C1-X <u C2 -> (X|(C2-1)) == C1
C1-X >u C2 -> (X|C2) == C1
X-C1 <u C2 -> (X & -C2) == C1
X-C1 >u C2 -> (X & ~C2) == C1


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185909 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index f4734461a62..d843842cb3a 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1512,6 +1512,30 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
         return R;
     break;
 
+  case Instruction::Sub: {
+    ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(0));
+    if (!LHSC) break;
+    const APInt &LHSV = LHSC->getValue();
+
+    // C1-X <u C2 -> (X|(C2-1)) == C1
+    //   iff C1 & (C2-1) == C2-1
+    //       C2 is a power of 2
+    if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
+        RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == (RHSV - 1))
+      return new ICmpInst(ICmpInst::ICMP_EQ,
+                          Builder->CreateOr(LHSI->getOperand(1), RHSV - 1),
+                          LHSC);
+
+    // C1-X >u C2 -> (X|C2) == C1
+    //   iff C1 & C2 == C2
+    //       C2+1 is a power of 2
+    if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
+        (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == RHSV)
+      return new ICmpInst(ICmpInst::ICMP_NE,
+                          Builder->CreateOr(LHSI->getOperand(1), RHSV), LHSC);
+    break;
+  }
+
   case Instruction::Add:
     // Fold: icmp pred (add X, C1), C2
     if (!ICI.isEquality()) {
@@ -1708,6 +1732,24 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
       default:
         break;
       }
+
+      // X-C1 <u C2 -> (X & -C2) == C1
+      //   iff C1 & (C2-1) == 0
+      //       C2 is a power of 2
+      if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
+          RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == 0)
+        return new ICmpInst(ICmpInst::ICMP_EQ,
+                            Builder->CreateAnd(LHSI->getOperand(0), -RHSV),
+                            ConstantExpr::getNeg(LHSC));
+
+      // X-C1 >u C2 -> (X & ~C2) == C1
+      //   iff C1 & C2 == 0
+      //       C2+1 is a power of 2
+      if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
+          (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == 0)
+        return new ICmpInst(ICmpInst::ICMP_NE,
+                            Builder->CreateAnd(LHSI->getOperand(0), ~RHSV),
+                            ConstantExpr::getNeg(LHSC));
     }
   }
   return 0;
diff --git a/test/Transforms/InstCombine/2007-01-27-AndICmp.ll b/test/Transforms/InstCombine/2007-01-27-AndICmp.ll
index 4d1b982f676..6298a072333 100644
--- a/test/Transforms/InstCombine/2007-01-27-AndICmp.ll
+++ b/test/Transforms/InstCombine/2007-01-27-AndICmp.ll
@@ -1,8 +1,8 @@
 ; RUN: opt < %s -instcombine -S | grep "ugt.*, 1"
 
 define i1 @test(i32 %tmp1030) {
-	%tmp1037 = icmp ne i32 %tmp1030, 40		; <i1> [#uses=1]
-	%tmp1039 = icmp ne i32 %tmp1030, 41		; <i1> [#uses=1]
+	%tmp1037 = icmp ne i32 %tmp1030, 39		; <i1> [#uses=1]
+	%tmp1039 = icmp ne i32 %tmp1030, 40		; <i1> [#uses=1]
 	%tmp1042 = and i1 %tmp1037, %tmp1039		; <i1> [#uses=1]
 	ret i1 %tmp1042
 }
diff --git a/test/Transforms/InstCombine/and.ll b/test/Transforms/InstCombine/and.ll
index 8492df9a120..3d36bfb404d 100644
--- a/test/Transforms/InstCombine/and.ll
+++ b/test/Transforms/InstCombine/and.ll
@@ -186,9 +186,9 @@ define i1 @test25(i32 %A) {
 }
 
 define i1 @test26(i32 %A) {
-        %B = icmp ne i32 %A, 50         ; <i1> [#uses=1]
-        %C = icmp ne i32 %A, 51         ; <i1> [#uses=1]
-        ;; (A-50) > 1
+        %B = icmp ne i32 %A, 49         ; <i1> [#uses=1]
+        %C = icmp ne i32 %A, 50         ; <i1> [#uses=1]
+        ;; (A-49) > 1
         %D = and i1 %B, %C              ; <i1> [#uses=1]
         ret i1 %D
 }
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index cf8305df2a9..aaac9b64939 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -1123,3 +1123,43 @@ define i1 @icmp_add_ult_2(i32 %X) {
   %cmp = icmp ult i32 %add, 2
   ret i1 %cmp
 }
+
+; CHECK: @icmp_add_X_-14_ult_2
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %X, -2
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp eq i32 [[AND]], 14
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_add_X_-14_ult_2(i32 %X) {
+  %add = add i32 %X, -14
+  %cmp = icmp ult i32 %add, 2
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_sub_3_X_ult_2
+; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %X, 1
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp eq i32 [[OR]], 3
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_sub_3_X_ult_2(i32 %X) {
+  %add = sub i32 3, %X
+  %cmp = icmp ult i32 %add, 2
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_add_X_-14_uge_2
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %X, -2
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp ne i32 [[AND]], 14
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_add_X_-14_uge_2(i32 %X) {
+  %add = add i32 %X, -14
+  %cmp = icmp uge i32 %add, 2
+  ret i1 %cmp
+}
+
+; CHECK: @icmp_sub_3_X_uge_2
+; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %X, 1
+; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp ne i32 [[OR]], 3
+; CHECK-NEXT: ret i1 [[CMP]]
+define i1 @icmp_sub_3_X_uge_2(i32 %X) {
+  %add = sub i32 3, %X
+  %cmp = icmp uge i32 %add, 2
+  ret i1 %cmp
+}