commit 26c8dcc692fb2addd475446cfff24d6a4e958bca
author Rafael Espindola <rafael.espindola@gmail.com> Wed Apr 04 12:51:34 2012 +0000
committer Rafael Espindola <rafael.espindola@gmail.com> Wed Apr 04 12:51:34 2012 +0000
tree b71cb0d781e2735397c728f276f14ea63780d04c
parent 00b73a5e443d49d68f59a5fb517e940842423ae6

Always compute all the bits in ComputeMaskedBits.
This allows us to keep passing reduced masks to SimplifyDemandedBits, but
know about all the bits if SimplifyDemandedBits fails. This allows instcombine
to simplify cases like the one in the included testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154011 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineCalls.cpp

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index b550fe8..77e4727 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -361,8 +361,7 @@
     uint32_t BitWidth = IT->getBitWidth();
     APInt KnownZero(BitWidth, 0);
     APInt KnownOne(BitWidth, 0);
-    ComputeMaskedBits(II->getArgOperand(0), APInt::getAllOnesValue(BitWidth),
-                      KnownZero, KnownOne);
+    ComputeMaskedBits(II->getArgOperand(0), KnownZero, KnownOne);
     unsigned TrailingZeros = KnownOne.countTrailingZeros();
     APInt Mask(APInt::getLowBitsSet(BitWidth, TrailingZeros));
     if ((Mask & KnownZero) == Mask)
@@ -380,8 +379,7 @@
     uint32_t BitWidth = IT->getBitWidth();
     APInt KnownZero(BitWidth, 0);
     APInt KnownOne(BitWidth, 0);
-    ComputeMaskedBits(II->getArgOperand(0), APInt::getAllOnesValue(BitWidth),
-                      KnownZero, KnownOne);
+    ComputeMaskedBits(II->getArgOperand(0), KnownZero, KnownOne);
     unsigned LeadingZeros = KnownOne.countLeadingZeros();
     APInt Mask(APInt::getHighBitsSet(BitWidth, LeadingZeros));
     if ((Mask & KnownZero) == Mask)
@@ -394,17 +392,16 @@
     Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
     IntegerType *IT = cast<IntegerType>(II->getArgOperand(0)->getType());
     uint32_t BitWidth = IT->getBitWidth();
-    APInt Mask = APInt::getSignBit(BitWidth);
     APInt LHSKnownZero(BitWidth, 0);
     APInt LHSKnownOne(BitWidth, 0);
-    ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
+    ComputeMaskedBits(LHS, LHSKnownZero, LHSKnownOne);
     bool LHSKnownNegative = LHSKnownOne[BitWidth - 1];
     bool LHSKnownPositive = LHSKnownZero[BitWidth - 1];
 
     if (LHSKnownNegative || LHSKnownPositive) {
       APInt RHSKnownZero(BitWidth, 0);
       APInt RHSKnownOne(BitWidth, 0);
-      ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
+      ComputeMaskedBits(RHS, RHSKnownZero, RHSKnownOne);
       bool RHSKnownNegative = RHSKnownOne[BitWidth - 1];
       bool RHSKnownPositive = RHSKnownZero[BitWidth - 1];
       if (LHSKnownNegative && RHSKnownNegative) {
@@ -488,14 +485,13 @@
   case Intrinsic::umul_with_overflow: {
     Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
     unsigned BitWidth = cast<IntegerType>(LHS->getType())->getBitWidth();
-    APInt Mask = APInt::getAllOnesValue(BitWidth);
 
     APInt LHSKnownZero(BitWidth, 0);
     APInt LHSKnownOne(BitWidth, 0);
-    ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
+    ComputeMaskedBits(LHS, LHSKnownZero, LHSKnownOne);
     APInt RHSKnownZero(BitWidth, 0);
     APInt RHSKnownOne(BitWidth, 0);
-    ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
+    ComputeMaskedBits(RHS, RHSKnownZero, RHSKnownOne);
 
     // Get the largest possible values for each operand.
     APInt LHSMax = ~LHSKnownZero;