[InstSimplify] Teach decomposeBitTestICmp to handle non-canonical compares

This adds support non-canonical compare predicates. InstSimplify can't rely on canonicalization to have occurred.

Differential Revision: https://reviews.llvm.org/D36646

llvm-svn: 310893

1 files changed, 28 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/CmpInstAnalysis.cpp b/llvm/lib/Analysis/CmpInstAnalysis.cpp
index 079811fe9a2..c879b8729dc 100644
--- a/llvm/lib/Analysis/CmpInstAnalysis.cpp
+++ b/llvm/lib/Analysis/CmpInstAnalysis.cpp
@@ -81,6 +81,13 @@ bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
     Mask = APInt::getSignMask(C->getBitWidth());
     Pred = ICmpInst::ICMP_NE;
     break;
+  case ICmpInst::ICMP_SLE:
+    // X <= -1 is equivalent to (X & SignMask) != 0.
+    if (!C->isAllOnesValue())
+      return false;
+    Mask = APInt::getSignMask(C->getBitWidth());
+    Pred = ICmpInst::ICMP_NE;
+    break;
   case ICmpInst::ICMP_SGT:
     // X > -1 is equivalent to (X & SignMask) == 0.
     if (!C->isAllOnesValue())
@@ -88,6 +95,13 @@ bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
     Mask = APInt::getSignMask(C->getBitWidth());
     Pred = ICmpInst::ICMP_EQ;
     break;
+  case ICmpInst::ICMP_SGE:
+    // X >= 0 is equivalent to (X & SignMask) == 0.
+    if (!C->isNullValue())
+      return false;
+    Mask = APInt::getSignMask(C->getBitWidth());
+    Pred = ICmpInst::ICMP_EQ;
+    break;
   case ICmpInst::ICMP_ULT:
     // X <u 2^n is equivalent to (X & ~(2^n-1)) == 0.
     if (!C->isPowerOf2())
@@ -95,6 +109,13 @@ bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
     Mask = -*C;
     Pred = ICmpInst::ICMP_EQ;
     break;
+  case ICmpInst::ICMP_ULE:
+    // X <=u 2^n-1 is equivalent to (X & ~(2^n-1)) == 0.
+    if (!(*C + 1).isPowerOf2())
+      return false;
+    Mask = ~*C;
+    Pred = ICmpInst::ICMP_EQ;
+    break;
   case ICmpInst::ICMP_UGT:
     // X >u 2^n-1 is equivalent to (X & ~(2^n-1)) != 0.
     if (!(*C + 1).isPowerOf2())
@@ -102,6 +123,13 @@ bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
     Mask = ~*C;
     Pred = ICmpInst::ICMP_NE;
     break;
+  case ICmpInst::ICMP_UGE:
+    // X >=u 2^n is equivalent to (X & ~(2^n-1)) != 0.
+    if (!C->isPowerOf2())
+      return false;
+    Mask = -*C;
+    Pred = ICmpInst::ICMP_NE;
+    break;
   }
 
   X = LHS;