commit 9115cf8c9dc23e3a9bd0e915f426b4fc694cd133
author Sanjay Patel <spatel@rotateright.com> Thu Oct 08 16:56:55 2015 +0000
committer Sanjay Patel <spatel@rotateright.com> Thu Oct 08 16:56:55 2015 +0000
tree 08fe8f3380b4e09941e8696311d7747fb03c8d93
parent aac75382160bb19e7d58c8d3af15ee629eaa860d

[ValueTracking] teach computeKnownBits that a fabs() clears sign bits

This was requested in D13076: if we're going to canonicalize to fabs(), ValueTracking
should know that fabs() clears sign bits.

In this patch (as in D13076), we're not handling vectors yet even though computeKnownBits'
fabs() case itself should be vector-ready via the splat in this patch. 
Fixing this will require follow-on patches to correct other logic that uses 'getScalarType'.

Differential Revision: http://reviews.llvm.org/D13222

llvm-svn: 249701

llvm/lib/Analysis/ValueTracking.cpp

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d8a4491..2259d87 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1065,7 +1065,8 @@
   }
   case Instruction::BitCast: {
     Type *SrcTy = I->getOperand(0)->getType();
-    if ((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
+    if ((SrcTy->isIntegerTy() || SrcTy->isPointerTy() ||
+         SrcTy->isFloatingPointTy()) &&
         // TODO: For now, not handling conversions like:
         // (bitcast i64 %x to <2 x i32>)
         !I->getType()->isVectorTy()) {
@@ -1378,6 +1379,12 @@
         KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
         break;
       }
+      case Intrinsic::fabs: {
+        Type *Ty = II->getType();
+        APInt SignBit = APInt::getSignBit(Ty->getScalarSizeInBits());
+        KnownZero |= APInt::getSplat(Ty->getPrimitiveSizeInBits(), SignBit);
+        break;
+      }
       case Intrinsic::x86_sse42_crc32_64_64:
         KnownZero |= APInt::getHighBitsSet(64, 32);
         break;
@@ -1477,8 +1484,9 @@
   unsigned BitWidth = KnownZero.getBitWidth();
 
   assert((V->getType()->isIntOrIntVectorTy() ||
+          V->getType()->isFPOrFPVectorTy() ||
           V->getType()->getScalarType()->isPointerTy()) &&
-         "Not integer or pointer type!");
+         "Not integer, floating point, or pointer type!");
   assert((DL.getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) &&
          (!V->getType()->isIntOrIntVectorTy() ||
           V->getType()->getScalarSizeInBits() == BitWidth) &&