[llvm] r279263 - [InstCombine] use m_APInt to allow icmp X, C folds for splat constant vectors

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Fri Aug 19 10:40:44 2016
New Revision: 279263

URL: http://llvm.org/viewvc/llvm-project?rev=279263&view=rev
Log:
[InstCombine] use m_APInt to allow icmp X, C folds for splat constant vectors

Of course, we really need to refactor and fix all of the cmp predicates, 
but this one is interesting because without it, we later perform an 
information-losing transform of icmp (shl 1, Y), C, and we can't recover
the better fold.

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

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=279263&r1=279262&r2=279263&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Fri Aug 19 10:40:44 2016
@@ -3622,25 +3622,30 @@ Instruction *InstCombiner::visitICmpInst
                            Constant::getAllOnesValue(Op0->getType()));
       }
       break;
-    case ICmpInst::ICMP_UGT:
+    case ICmpInst::ICMP_UGT: {
       if (Op0Min.ugt(Op1Max))          // A >u B -> true if min(A) > max(B)
         return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
+
       if (Op0Max.ule(Op1Min))          // A >u B -> false if max(A) <= max(B)
         return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
 
       if (Op1Max == Op0Min)            // A >u B -> A != B if min(A) == max(B)
         return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
-      if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
-        if (Op1Min == Op0Max-1)        // A >u C -> A == C+1 if max(a)-1 == C
+
+      const APInt *CmpC;
+      if (match(Op1, m_APInt(CmpC))) {
+        // A >u C -> A == C+1 if max(a)-1 == C
+        if (*CmpC == Op0Max - 1)
           return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
-                              Builder->getInt(CI->getValue()+1));
+                              ConstantInt::get(Op1->getType(), *CmpC + 1));
 
         // (x >u 2147483647) -> (x <s 0)  -> true if sign bit set
-        if (CI->isMaxValue(true))
+        if (CmpC->isMaxSignedValue())
           return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
                               Constant::getNullValue(Op0->getType()));
       }
       break;
+    }
     case ICmpInst::ICMP_SLT:
       if (Op0Max.slt(Op1Min))          // A <s B -> true if max(A) < min(C)
         return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=279263&r1=279262&r2=279263&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Fri Aug 19 10:40:44 2016
@@ -1672,7 +1672,7 @@ define i1 @icmp_shl_1_V_uge_2147483648(i
 define <2 x i1> @icmp_shl_1_V_uge_2147483648_vec(<2 x i32> %V) {
 ; CHECK-LABEL: @icmp_shl_1_V_uge_2147483648_vec(
 ; CHECK-NEXT:    [[SHL:%.*]] = shl <2 x i32> <i32 1, i32 1>, %V
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt <2 x i32> [[SHL]], <i32 2147483647, i32 2147483647>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt <2 x i32> [[SHL]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %shl = shl <2 x i32> <i32 1, i32 1>, %V
@@ -2591,6 +2591,10 @@ define i1 @ugtMaxSignedVal(i8 %a) {
 }
 
 define <2 x i1> @ugtMaxSignedValVec(<2 x i8> %a) {
+; CHECK-LABEL: @ugtMaxSignedValVec(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt <2 x i8> %a, zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[CMP]]
+;
   %cmp = icmp ugt <2 x i8> %a, <i8 127, i8 127>
   ret <2 x i1> %cmp
 }
@@ -2609,7 +2613,7 @@ define i1 @ugtKnownBits(i8 %a) {
 define <2 x i1> @ugtKnownBitsVec(<2 x i8> %a) {
 ; CHECK-LABEL: @ugtKnownBitsVec(
 ; CHECK-NEXT:    [[B:%.*]] = and <2 x i8> %a, <i8 17, i8 17>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt <2 x i8> [[B]], <i8 16, i8 16>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i8> [[B]], <i8 17, i8 17>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %b = and <2 x i8> %a, <i8 17, i8 17>